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  • 51.
    Broman, Barry
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Peterson, Carsten
    SMHI.
    Spridningsundersökningar i yttre fjärden Piteå1985Rapport (Annet vitenskapelig)
    Abstract [sv]

    Sveriges Meteorologiska och Hydrologiska Institut (SMHI) får i september 1984 i uppdrag av SCA, Piteå-Munksund att undersöka utspädnings- och spridningsförhållandena för avloppsvattnet från SCAs Munksundsindustri.

    Under åren 1981 och 1982 utförs strömundersökningar i Yttre fjärden, Piteå, för att med detta som underlag kunna simulera spridningen av avloppsvattnet från Munksundsindustrin (ref nr 8).

    En ändring av utsläppets läge görs i maj 1982 och ytterligare förändringar sker senare under året genom att länsor och strömbildare läggs ut, i syfte att föra avloppsvattnet i ett samlat stråk ut i Piteälvens strömfåra. SMHI rekommenderar, med ledning av strömundersökningarna 1981-82, att en avloppsledning skall dras ut centralt i fjärden med en utsläppsnivå ovan 6 meters djup, dvs ovan språngskiktet.

    Enligt beslut av Länsstyrelsen i Norrbotten i november 1983 (bilaga 1), skall SMHI, i enlighet med Länsstyrelsens anvisningar och på uppdrag av SCA, studera utspädnings- och spridningsförhållandena med hjälp av spårämne.

  • 52.
    Bärring, Lars
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Berlin, Mats
    Andersson Gull, Bengt
    Tailored climate indices for climate-proofing operational forestry applications in Sweden and Finland2017Inngår i: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 37, nr 1, s. 123-142Artikkel i tidsskrift (Fagfellevurdert)
  • 53.
    Bärring, Lars
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Christensen, Jens
    Déqué, Michel
    Giorgi, Filippo
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Richard
    Laprise, René
    Rummukainen, Markku
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    von Storch, Hans
    Synthesis of Workshop2005Inngår i: Extended abstracts of a WMO/WCRP-sponsored Regional-Scale Climate Modelling Workshop : high-resolution climate modelling : assessment, added value and applications, Lund, Sweden, 29 March-2 April 2004 / [ed] Bärring, Lars; René, Laprise, Department of Physical Geography & Ecosystem Analysis, Lund University, Sweden , 2005, s. 18-25Konferansepaper (Annet vitenskapelig)
  • 54.
    Bärring, Lars
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Fortuniak, Krzysztof
    Multi-indices analysis of southern Scandinavian storminess 1780-2005 and links to interdecadal variations in the NW Europe-North Sea region2009Inngår i: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 29, nr 3, s. 373-384Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Extra-tropical cyclone frequency and intensity are Currently under intense scrutiny because of the destruction recent windstorms have brought to Europe, and because they are a major meridional heat transport mechanism that may respond to differential latitudinal warming trends. Several studies using reanalysis data covering the second half of the 20th century Suggest increasing storm intensity in the northeastern Atlantic and European sector. Fewer analyses cover a longer time period but show different trends or point towards the dominance of interdecadal variability instead of ally clear trends. Hence, it is relevant to analyse cyclone variability over as long a period as possible. In this Study, we analyse interdecadal variability in cyclone activity over northwestern Europe back to AD 1780 by combining information from eight storminess indices applied in all Eulerian framework. These indices, including four new approaches towards gauging cyclone activity, use the series of thrice-daily sea level pressure observations at Lund and Stockholm. We find pronounced interdecadal variability in cyclonic activity but no significant overall consistent long-term trend. The major interdecadal-scale variability common to all indices is in good agreement with geostrophic wind reconstructions for NE Atlantic and NW Europe, and with variations in the North Atlantic oscillation (NAO). Our results show that the reanalysis studies cover a time period chiefly coinciding with a marked, but not exceptional in our 225-year perspective, positive variation in the regional cyclone activity that has more recently reversed. Because of the interdecadal variations, a near-centennial time perspective is needed when analysing variations in extra-tropical cyclone activity and the associated weather conditions over northwestern Europe. Copyright (C) 2009 Royal Meteorological Society

  • 55.
    Bärring, Lars
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Holt, Tom
    Linderson, Maj-Lena
    Radziejewski, Madej
    Moriondo, Marco
    Palutikof, Jean P.
    Defining dry/wet spells for point observations, observed area averages, and regional climate model gridboxes in Europe2006Inngår i: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 31, nr 1, s. 35-49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new method for optimising threshold values of dry/wet spells is evaluated. A set of indices is used to find the best threshold giving good correspondence between the frequency of dry/wet spells in Hadley Centre regional model (HadRM3) output, reference observations with predetermined thresholds, and area-averaged observations. The analyses focus on selected model gridboxes in 3 different European climate regimes (Sweden, UK, Italy), where station data are available from several locations. In addition, a pan-European analysis using the European Climate Assessment (ECA) dataset is carried out. Generally, there is good agreement between point observations and the corresponding area average using the common thresholds of 0.1 or 1.0 mm with observational data. Applying the optimal thresholds on the model output is important, as it typically results in substantially better agreement between the simulated and observed series of dry/wet days. The fitted optimal pan-European dry/wet threshold is (1) 0.47 or 0.15 mm, depending on model version, for the observed point data threshold of 0.1 mm, and (2) 1.2 or 0.56 mm, depending on model version, for the threshold of 1.0 mm.

  • 56.
    Bärring, Lars
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jonsson, P
    Achberger, C
    Ekstrom, M
    Alexandersson, Hans
    SMHI.
    The Lund instrumental record of meteorological observations: Reconstruction of monthly sea-level pressure 1780-19971999Inngår i: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 19, nr 13, s. 1427-1443Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reconstructed surface air pressure series from Lund, southern Sweden, covers the period 1780-1997 and comprises mon than 234000 valid observations (three observations per day), i.e. > 98% of all possible observation occasions. For the Early Instrumental Period (EIP; 1780-1860) data were digitised from the original records. For most of the Modern Instrumental Period (MIP; 1861-) a series was compiled from various databases containing instrument corrected data. During EIP, the series of raw monthly means show several substantial inhomogeneities. With the aid of a detailed reconstruction of the station history, it was possible to remove almost all inhomogeneities during EIP by applying the correct instrument corrections (for barometer temperature, to standard gravity and to mean sea-level pressure) to the series of original observations. In particular, corrections for the temperature and altitude of the barometer eliminated several inhomogeneities. A prerequisite for applying these corrections is the availability of high-resolution data (actual raw observations or daily averages). Further homogenisation was attained by intercomparison of the monthly mean pressure with acknowledged homogeneous series (mainly the UKMO monthly grid, station records from Copenhagen and Edinburgh). Statistical tests of homogeneity showed that no substantial inhomogeneities remain in the final version. The modern part of the final monthly pressure series largely follows that of the southern Baltic Sea region. Furthermore, it shows relatively high pressure during spring (MAM) in the period 1780-1820, which was paralleled by severe wind erosion in southern Scandinavia during this time. Relatively high pressure throughout the year is also notable during a period of precipitation deficit in 1970s. Copyright (C) 1999 Royal Meteorological Society.

  • 57.
    Bärring, Lars
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Persson, Gunn
    SMHI, Affärsverksamhet.
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Samuelsson, Patrick
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Evaluation of climate extremes in transient runs with the new Rossby Centre regional atmospheric model.2006Inngår i: Abstracts of the contributions of the EGU General Assembly 2006, EGU06-A-10110, 2006Konferansepaper (Annet vitenskapelig)
  • 58.
    Bärring, Lars
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Strandberg, Gustav
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Does the projected pathway to global warming targets matter?2018Inngår i: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 13, nr 2, artikkel-id 024029Artikkel i tidsskrift (Fagfellevurdert)
  • 59.
    Bärring, Lars
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    von Storch, H
    Scandinavian storminess since about 18002004Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 31, nr 20, artikkel-id L20202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the history of storminess in Northern Europe, as derived from local pressure observations in Lund since 1780 and Stockholm since 1820 ( Sweden). At both stations barometer readings were made three times per day, morning, midday and evening, and after about 1850 at fixed observation hours. We use four common storminess indices: annual number of deep lows ( p < 980 hPa), the annual 95th and 99th percentile of pressure changes between two observations, and the annual number of fast absolute pressure changes (\&UDelta;p\/&UDelta;t > 16 hPa/12 h). It turns out that the 1980' s - mid 1990' s were a period of enhanced storminess, mainly seen in the Stockholm record, but his period is within the natural variability of the records. Thus, there are no robust signs of any long-term trend in the storminess indices. Storminess is during the entire historical period remarkably stable, with no systematic change and little transient variability.

  • 60.
    Caian, Mihaela
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Koenigk, Torben
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Doescher, Ralf
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Devasthale, Abhay
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation2018Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, nr 1-2, s. 423-441Artikkel i tidsskrift (Fagfellevurdert)
  • 61.
    Caian, Mihaela
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Koenigk, Torben
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Doescher, Ralf
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Devasthale, Abhay
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation (vol 50, pg 423, 2017)2018Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, nr 1-2, s. 443-443Artikkel i tidsskrift (Fagfellevurdert)
  • 62.
    Caron, Louis-Philippe
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre. Climate Forecasting Unit, Institut Cátála de Ciènces del clima (IC3).
    Boudreault, Mathieu
    Bruyere, Cindy L.
    Changes in large-scale controls of Atlantic tropical cyclone activity with the phases of the Atlantic multidecadal oscillation2015Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 44, nr 7-8, s. 1801-1821Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Atlantic tropical cyclone activity is known to oscillate between multi-annual periods of high and low activity. These changes have been linked to the Atlantic multidecadal oscillation (AMO), a mode of variability in Atlantic sea surface temperature which modifies the large-scale conditions of the tropical Atlantic. Cyclone activity is also modulated at higher frequencies by a series of other climate factors, with some of these influences appearing to be more consistent than others. Using the HURDAT2 database and a second set of tropical cyclone data corrected for possible missing storms in the earlier part of the record, we investigate, through Poisson regressions, the relationship between a series of climate variables and a series of metrics of seasonal Atlantic cyclone activity during both phases of the AMO. We find that, while some influences, such as El Nino Southern oscillation, remain present regardless of the AMO phase, other climate factors show an influence during only one of the two phases. During the negative phase, Sahel precipitation and the North Atlantic oscillation (NAO) are measured to play a role, while during the positive phase, the 11-year solar cycle and dust concentration over the Atlantic appear to be more important. Furthermore, we show that during the negative phase of the AMO, the NAO influences all our measures of tropical cyclone activity, and we go on to provide evidence that this is not simply due to changes in steering current, the mechanism by which the NAO is usually understood to impact Atlantic cyclone activity. Finally, we conclude by demonstrating that our results are robust to the sample size as well as to the choice of the statistical model.

  • 63. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Analysing present, past and future tropical cyclone activity as inferred from an ensemble of Coupled Global Climate Models2008Inngår i: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 60, nr 1, s. 80-96Artikkel i tidsskrift (Fagfellevurdert)
  • 64. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Understanding and simulating the link between African easterly waves and Atlantic tropical cyclones using a regional climate model: the role of domain size and lateral boundary conditions2012Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, nr 1-2, s. 113-135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using a suite of lateral boundary conditions, we investigate the impact of domain size and boundary conditions on the Atlantic tropical cyclone and african easterly Wave activity simulated by a regional climate model. Irrespective of boundary conditions, simulations closest to observed climatology are obtained using a domain covering both the entire tropical Atlantic and northern African region. There is a clear degradation when the high-resolution model domain is diminished to cover only part of the African continent or only the tropical Atlantic. This is found to be the result of biases in the boundary data, which for the smaller domains, have a large impact on TC activity. In this series of simulations, the large-scale Atlantic atmospheric environment appears to be the primary control on simulated TC activity. Weaker wave activity is usually accompanied by a shift in cyclogenesis location, from the MDR to the subtropics. All ERA40-driven integrations manage to capture the observed interannual variability and to reproduce most of the upward trend in tropical cyclone activity observed during that period. When driven by low-resolution global climate model (GCM) integrations, the regional climate model captures interannual variability (albeit with lower correlation coefficients) only if tropical cyclones form in sufficient numbers in the main development region. However, all GCM-driven integrations fail to capture the upward trend in Atlantic tropical cyclone activity. In most integrations, variations in Atlantic tropical cyclone activity appear uncorrelated with variations in African easterly wave activity.

  • 65. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Doblas-Reyes, Francisco
    Multi-year prediction skill of Atlantic hurricane activity in CMIP5 decadal hindcasts2014Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 42, nr 9-10, s. 2675-2690Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using a statistical relationship between simulated sea surface temperature and Atlantic hurricane activity, we estimate the skill of a CMIP5 multi-model ensemble at predicting multi-annual level of Atlantic hurricane activity. The series of yearly-initialized hindcasts show positive skill compared to simpler forecasts such as persistence and climatology as well as non-initialized forecasts and return anomaly correlation coefficients of similar to 0.6 and similar to 0.8 for five and nine year forecasts, respectively. Some skill is shown to remain in the later years and making use of those later years to create a lagged-ensemble yields, for individual models, results that approach that obtained by the multi-model ensemble. Some of the skill is shown to come from persisting rather than predicting the climate shift that occur in 1994-1995. After accounting for that shift, the anomaly correlation coefficient for five-year forecasts is estimated to drop to 0.4, but remains statistically significant up to lead years 3-7. Most of the skill is shown to come from the ability of the forecast systems at capturing change in Atlantic sea surface temperature, although the failure of most systems at reproducing the observed slow down in warming over the tropics in recent years leads to an underestimation of hurricane activity in the later period.

  • 66.
    Caron, Louis-Philippe
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Vaillancourt, Paul A.
    Winger, Katja
    On the relationship between cloud-radiation interaction, atmospheric stability and Atlantic tropical cyclones in a variable-resolution climate model2013Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 40, nr 5-6, s. 1257-1269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We compare two 28-year simulations performed with two versions of the Global Environmental Multiscale model run in variable-resolution mode. The two versions differ only by small differences in their radiation scheme. The most significant modification introduced is a reduction in the ice effective radius, which is observed to increase absorption of upwelling infrared radiation and increase temperature in the upper troposphere. The resulting change in vertical lapse rate is then observed to drive a resolution-dependent response of convection, which in turn modifies the zonal circulation and induces significant changes in simulated Atlantic tropical cyclone activity. The resulting change in vertical lapse rate and its implication in the context of anthropogenic climate change are discussed.

  • 67.
    Caron, Louis-Philippe
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Winger, Katja
    Impact of resolution and downscaling technique in simulating recent Atlantic tropical cylone activity2011Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 37, nr 5-6, s. 869-892Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using the global environmental multiscale (GEM) model, we investigate the impact of increasing model resolution from 2A degrees to 0.3A degrees on Atlantic tropical cyclone activity. There is a clear improvement in the realism of Atlantic storms with increased resolution, in part, linked to a better representation of African easterly waves. The geographical distribution of a Genesis Potential Index, composed of large-scales fields known to impact cyclone formation, coincides closely in the model with areas of high cyclogenesis. The geographical distribution of this index also improves with resolution. We then compare two techniques for achieving local high resolution over the tropical Atlantic: a limited-area model driven at the boundaries by the global 2A degrees GEM simulation and a global variable resolution model (GVAR). The limited-area domain and high-resolution part of the GVAR model coincide geographically, allowing a direct comparison between these two downscaling options. These integrations are further compared with a set of limited-area simulations employing the same domain and resolution, but driven at the boundaries by reanalysis. The limited-area model driven by reanalysis produces the most realistic Atlantic tropical cyclone variability. The GVAR simulation is clearly more accurate than the limited-area version driven by GEM-Global. Degradation in the simulated interannual variability is partly linked to the models failure to accurately reproduce the impact of atmospheric teleconnections from the equatorial Pacific and Sahel on Atlantic cyclogenesis. Through the use of a smaller limited-area grid, driven by GEM-Global 2A degrees, we show that an accurate representation of African Easterly Waves is crucial for simulating Atlantic tropical cyclone variability.

  • 68. Carril, A. F.
    et al.
    Menendez, C. G.
    Remedio, A. R. C.
    Robledo, F.
    Soerensson, A.
    Tencer, B.
    Boulanger, J. -P
    de Castro, M.
    Jacob, D.
    Le Treut, H.
    Li, L. Z. X.
    Penalba, O.
    Pfeifer, S.
    Rusticucci, M.
    Salio, P.
    Samuelsson, Patrick
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Sanchez, E.
    Zaninelli, P.
    Performance of a multi-RCM ensemble for South Eastern South America2012Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, nr 12, s. 2747-2768Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ability of four regional climate models to reproduce the present-day South American climate is examined with emphasis on La Plata Basin. Models were integrated for the period 1991-2000 with initial and lateral boundary conditions from ERA-40 Reanalysis. The ensemble sea level pressure, maximum and minimum temperatures and precipitation are evaluated in terms of seasonal means and extreme indices based on a percentile approach. Dispersion among the individual models and uncertainties when comparing the ensemble mean with different climatologies are also discussed. The ensemble mean is warmer than the observations in South Eastern South America (SESA), especially for minimum winter temperatures with errors increasing in magnitude towards the tails of the distributions. The ensemble mean reproduces the broad spatial pattern of precipitation, but overestimates the convective precipitation in the tropics and the orographic precipitation along the Andes and over the Brazilian Highlands, and underestimates the precipitation near the monsoon core region. The models overestimate the number of wet days and underestimate the daily intensity of rainfall for both seasons suggesting a premature triggering of convection. The skill of models to simulate the intensity of convective precipitation in summer in SESA and the variability associated with heavy precipitation events (the upper quartile daily precipitation) is far from satisfactory. Owing to the sparseness of the observing network, ensemble and observations uncertainties in seasonal means are comparable for some regions and seasons.

  • 69. Casanueva, A.
    et al.
    Kotlarski, S.
    Herrera, S.
    Fernandez, J.
    Gutierrez, J. M.
    Boberg, F.
    Colette, A.
    Christensen, O. B.
    Goergen, K.
    Jacob, D.
    Keuler, K.
    Nikulin, Grigory
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Teichmann, C.
    Vautard, R.
    Daily precipitation statistics in a EURO-CORDEX RCM ensemble: added value of raw and bias-corrected high-resolution simulations2016Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 47, nr 3-4, s. 719-737Artikkel i tidsskrift (Fagfellevurdert)
  • 70. Cavazos, Tereza
    et al.
    Luna-Nino, Rosa
    Cerezo-Mota, Ruth
    Fuentes Franco, Ramon
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Mendez, Matias
    Pineda Martinez, Luis Felipe
    Valenzuela, Ernesto
    Climatic trends and regional climate models intercomparison over the CORDEX-CAM (Central America, Caribbean, and Mexico) domain2019Inngår i: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An intercomparison of three regional climate models (RCMs) (PRECIS-HadRM3P, RCA4, and RegCM4) was performed over the Coordinated Regional Dynamical Experiment (CORDEX)-Central America, Caribbean, and Mexico (CAM) domain to determine their ability to reproduce observed temperature and precipitation trends during 1980-2010. Particular emphasis was given to the North American monsoon (NAM) and the mid-summer drought (MSD) regions. The three RCMs show negative (positive) temperature (precipitation) biases over the mountains, where observations have more problems due to poor data coverage. Observations from the Climate Research Unit (CRU) and ERA-Interim show a generalized warming over the domain. The most significant warming trend (>= 0.34 degrees C/decade) is observed in the NAM, which is moderately captured by the three RCMs, but with less intensity; each decade from 1970 to 2016 has become warmer than the previous ones, especially during the summer (mean and extremes); this warming appears partially related to the positive Atlantic Multidecadal Oscillation (+AMO). CRU, GPCP, and CHIRPS show significant decreases of precipitation (less than -15%/decade) in parts of the southwest United States and northwestern Mexico, including the NAM, and a positive trend (5-10%/decade) in June-September in eastern Mexico, the MSD region, and northern South America, but longer trends (1950-2017) are not statistically significant. RCMs are able to moderately simulate some of the recent trends, especially in winter. In spite of their mean biases, the RCMs are able to adequately simulate inter-annual and seasonal variations. Wet (warm) periods in regions affected by the MSD are significantly correlated with the +AMO and La Nina events (+AMO and El Nino). Summer precipitation trends from GPCP show opposite signs to those of CRU and CHIRPS over the Mexican coasts of the southern Gulf of Mexico, the Yucatan Peninsula, and Cuba, possibly due to data limitations and differences in grid resolutions.

  • 71. Cerezo-Mota, Ruth
    et al.
    Cavazos, Tereza
    Arritt, Raymond
    Torres-Alavez, Abraham
    Sieck, Kevin
    Nikulin, Grigory
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Moufouma-Okia, Wilfram
    Antonio Salinas-Prieto, Jose
    CORDEX-NA: factors inducing dry/wet years on the North American Monsoon region2016Inngår i: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 36, nr 2, s. 824-836Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The output of four regional climate models (RCMs) from the Coordinated Regional Climate Downscaling Experiment (CORDEX)-North America (NA) region was analysed for the 1990-2008 period, with particular interest on the mechanisms associated with wet and dry years over the North American Monsoon (NAM) core region. All RCMs (RCA3.5, HadGEM3-RA, REMO, and RegCM4) were forced by the ERA-Interim reanalysis. Model precipitation was compared against several observational gridded data sets at different time scales. Most RCMs capture well the annual cycle of precipitation and outperform ERA-Interim, which is drier than the observations. RCMs underestimate (overestimate) the precipitation over the coastal plains (mountains) and have some problems to reproduce the interannual variability of the monsoon. To further investigate this, two extreme summers that showed the largest consistency among observations and RCMs were chosen: one wet (1990) and one dry (2005). The impact of the passage of tropical cyclones, the size of the Western Hemisphere Warm Pool (WHWP), the Intertropical Convergence Zone (ITCZ) position, and the initial intensity of the land-sea thermal contrast (LSTC) were analysed. During the wet year, the LSTC was stronger than the 2005 dry monsoon season and there were a larger number of hurricanes near the Gulf of California, the WHWP was more extended, and the ITCZ was located in a more northerly position than in 2005. All these processes contributed to a wetter NAM season. During the dry year, the LSTC was weaker, with a later onset, probably due to a previous very wet winter. The inverse precipitation relationship between winter and summer in the monsoon region was well captured by most of the RCMs. RegCM4 showed the largest biases and HadGEM3-RA the smallest ones.

  • 72. Chadwick, R.
    et al.
    Martin, G. M.
    Copsey, D.
    Bellon, G.
    Caian, Mihaela
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Codron, F.
    Rio, C.
    Roehrig, R.
    Examining the West African Monsoon circulation response to atmospheric heating in a GCM dynamical core2017Inngår i: Journal of Advances in Modeling Earth Systems, ISSN 1942-2466, Vol. 9, nr 1, s. 149-167Artikkel i tidsskrift (Fagfellevurdert)
  • 73. Christensen, J H
    et al.
    Räisänen, Jouni
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Iversen, T
    Bjorge, D
    Christensen, O B
    Rummukainen, Markku
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    A synthesis of regional climate change simulations - A Scandinavian perspective2001Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 28, nr 6, s. 1003-1006Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Four downscaling experiments of regional climate change for the Nordic countries have been conducted with three different regional climate models (RCMs). A short synthesis of the outcome of the suite of experiments is presented as an ensemble, reflecting the different driving atmosphere-ocean general circulation model (AOGCM) conditions, RCM model resolution and domain size, and choice of emission scenarios. This allows the sources of uncertainties in the projections to be assessed. At the same time analysis of the climate change signal for temperature and precipitation over the period 1990-2050 reveals strong similarities. In particular, all experiments in the suite simulate changes in the precipitation distribution towards a higher frequency of heavy precipitation.

  • 74. Christensen, Jens H.
    et al.
    Carter, Timothy R.
    Rummukainen, Markku
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Amanatidis, Georgios
    Evaluating the performance and utility of regional climate models: the PRUDENCE project2007Inngår i: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 81, s. 1-6Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    This special issue of Climatic Change contains a series of research articles documenting coordinated work carried out within a 3-year European Union project 'Prediction of Regional scenarios and Uncertainties for Defining European Climate change risks and Effects' (PRUDENCE). The main objective of the PRUDENCE project was to provide high resolution climate change scenarios for Europe at the end of the twenty-first century by means of dynamical downscaling (regional climate modelling) of global climate simulations. The first part of the issue comprises seven overarching PRUDENCE papers on: (1) the design of the model simulations and analyses of climate model perfort-natice, (2 and 3) evaluation and intercomparison of simulated climate changes, (4 and 5) specialised analyses of impacts on water resources and on other sectors including agriculture, ecosystems, energy, and transport, (6) investigation of extreme weather events and (7) implications of the results for policy. A paper summarising the related MICE (Modelling the Impact of Climate Extremes) project is also included. The second part of the issue contains 12 articles that focus in more detail on some of the themes summarised in the overarching papers. The PRUDENCE results represent the first comprehensive, continental-scale intercomparison and evaluation of high resolution climate models and their applications, bringing together climate modelling, impact research and social sciences expertise on climate change.

  • 75. Christensen, Jens Hesselbjerg
    et al.
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Giorgi, Filippo
    Lenderink, Geert
    Rummukainen, Markku
    SMHI, Samhälle och säkerhet.
    Weight assignment in regional climate models2010Inngår i: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 44, nr 2-3, s. 179-194Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An important new development within the European ENSEMBLES project has been to explore performance-based weighting of regional climate models (RCMs). Until now, although no weighting has been applied in multi-RCM analyses, one could claim that an assumption of 'equal weight' was implicitly adopted. At the same time, different RCMs generate different results, e. g. for various types of extremes, and these results need to be combined when using the full RCM ensemble. The process of constructing, assigning and combining metrics of model performance is not straightforward. Rather, there is a considerable degree of subjectivity both in the choice of metrics and on how these may be combined into weights. We explore the applicability of combining a set of 6 specifically designed RCM performance metrics to produce one aggregated model weight with the purpose of combining climate change information from the range of RCMs used within ENSEMBLES. These metrics capture aspects of model performance in reproducing large-scale circulation patterns, meso-scale signals, daily temperature and precipitation distributions and extremes, trends and the annual cycle. We examine different aggregation procedures that generate different inter-model spreads of weights. The use of model weights is sensitive to the aggregation procedure and shows different sensitivities to the selected metrics. Generally, however, we do not find compelling evidence of an improved description of mean climate states using performance-based weights in comparison to the use of equal weights. We suggest that model weighting adds another level of uncertainty to the generation of ensemble-based climate projections, which should be suitably explored, although our results indicate that this uncertainty remains relatively small for the weighting procedures examined.

  • 76. Christensen, Ole Bossing
    et al.
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Zorita, Eduardo
    Projected Change-Atmosphere2015Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    This chapter builds on the comprehensive summary of climate change scenarios in the first BACC assessment published in 2008. This chapter first addresses the dynamical downscaling of general circulation model (GCM) results to the regional scale, focussing on results from 13 regional climate model (RCM) simulations in the ENSEMBLES project as this European-scale ensemble simulation is also relevant for the Baltic Sea region and many studies on temperature, precipitation, wind speed and snow amounts have been performed. This chapter then reviews statistical downscaling studies that use large-scale atmospheric variables (predictors) to estimate possible future change in several smaller scale fields (predictands), with the greatest emphasis given to hydrological variables (such as precipitation and run-off). For the Baltic Sea basin, the findings of the statistical downscaling studies are generally in line with studies employing dynamical downscaling.

  • 77. Clausen, Niels-Erik
    et al.
    Pryor, Sara C.
    Larsén, Xiaoli Guo
    Hyvönen, Reijo
    Venäläinen, Ari
    Suvilampi4, Elina
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Barthelmie, Rebecca
    Are we facing increasing extreme winds in the future?2009Konferansepaper (Annet vitenskapelig)
  • 78. Corrales-Suastegui, Arturo
    et al.
    Fuentes Franco, Ramon
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Pavia, Edgar G.
    The mid-summer drought over Mexico and Central America in the 21st century2019Inngår i: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The southern Mexico and Central America (SMCA) region shows a dominant well-defined precipitation annual cycle. The rainy season usually begins in May and ends in October, with a relatively dry period in July and August known as the mid-summer drought (MSD); notable exceptions are the Caribbean coast of Honduras and Costa Rica. This MSD phenomenon is expected to be affected as the SMCA experiences an enhanced differential warming between the Pacific and Atlantic Oceans (PO-AO) towards the end of the 21st century. Previous studies have suggested that this differential warming will induce a strengthening of the westward Caribbean low-level jet (CLLJ) and that this heightened CLLJ will shift precipitation westwards, falling on the PO instead that within the SMCA region causing a severe drought. In this work we examine this scenario with a new model, the Rossby Center Regional Climate Model (RCA4), for the COordinated Regional climate Downscaling EXperiment (CORDEX) Central America domain, forced with different general circulation models (GCMs) and for different representative concentration paths (RCPs). We consider 25-year periods as "present conditions" (1981-2005) and "future scenario" (2071-2095), focusing on the "extended summer" season (May-October). Results suggest that in the future the spatial extension of the MSD will decrease and that in certain areas the MSD will be more intense but less frequent compared to present conditions. Also, the oceanic differential warming, the intensification of the CLLJ, and the reduction in regional precipitation in the future scenario, suggested by previous works, were verified in this study.

  • 79. Couvreux, F.
    et al.
    Roehrig, R.
    Rio, C.
    Lefebvre, M. -P
    Caian, Mihaela
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Komori, T.
    Derbyshire, S.
    Guichard, F.
    Favot, F.
    D'Andrea, F.
    Bechtold, P.
    Gentine, P.
    Representation of daytime moist convection over the semi-arid Tropics by parametrizations used in climate and meteorological models2015Inngår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 141, nr 691, s. 2220-2236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A case of daytime development of deep convection over tropical semi-arid land is used to evaluate the representation of convection in global and regional models. The case is based on observations collected during the African Monsoon Multidisciplinary Analysis (AMMA) field campaign and includes two distinct transition phases, from clear sky to shallow cumulus and from cumulus to deep convection. Different types of models, run with identical initial and boundary conditions, are intercompared: a reference large-eddy simulation (LES), single-column model (SCM) version of four different Earth system models that participated in the Coupled Model Intercomparison Project 5 exercise, the SCM version of the European Centre for Medium-range Weather Forecasts operational forecast model, the SCM version of a mesoscale model and a bulk model. Surface fluxes and radiative heating are prescribed preventing any atmosphere-surface and cloud-radiation coupling in order to simplify the analyses so that it focuses only on convective processes. New physics packages are also evaluated within this framework. As the LES correctly reproduces the observed growth of the boundary layer, the gradual development of shallow clouds, the initiation of deep convection and the development of cold pools, it provides a basis to evaluate in detail the representation of the diurnal cycle of convection by the other models and to test the hypotheses underlying convective parametrizations. Most SCMs have difficulty in representing the timing of convective initiation and rain intensity, although substantial modifications to boundary-layer and deep-convection parametrizations lead to improvements. The SCMs also fail to represent the mid-level troposphere moistening during the shallow convection phase, which we analyse further. Nevertheless, beyond differences in timing of deep convection, the SCM models reproduce the sensitivity to initial and boundary conditions simulated in the LES regarding boundary-layer characteristics, and often the timing of convection triggering.

  • 80. Crewell, S
    et al.
    Bloemink, H
    Feijt, A
    Garcia, S G
    Jolivet, D
    Krasnov, O A
    van Lammeren, A
    Lohnert, J
    van Meijgaard, E
    Meywerk, J
    Quante, M
    Pfeilsticker, K
    Schmidt, S
    Scholl, T
    Simmer, C
    Schroder, M
    Trautmann, T
    Venema, V
    Wendisch, M
    Willén, Ulrika
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    The BALTEX Bridge Campaign - An integrated approach for a better understanding of clouds2004Inngår i: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 85, nr 10, s. 1565-+Artikkel i tidsskrift (Fagfellevurdert)
  • 81. Deandreis, Celine
    et al.
    Page, Christian
    Braconnot, Pascale
    Bärring, Lars
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Bucchignani, Edoardo
    de Cerff, Wim Som
    Hutjes, Ronald
    Joussaume, Sylvie
    Mares, Constantin
    Planton, Serge
    Plieger, Maarten
    Towards a dedicated impact portal to bridge the gap between the impact and climate communities: Lessons from use cases2014Inngår i: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 125, nr 3-4, s. 333-347Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Future climate evolution is of primary importance for the societal, economical, political orientations and decision-making. It explains the increasing use of climate projections as input for quantitative impact studies, assessing vulnerability and defining adaptation strategies in different sectors. Here we analyse 17 national and representative use cases so as to identify the diversity of the demand for climate information depending on user profiles as well as the best practices, methods and tools that are needed to answer the different requests. A particular emphasis is put on the workflow that allows to translate climate data into suitable impact data, the way to deal with the different sources of uncertainty and to provide a suited product to users. We identified three complementary tools to close the gap between climate scientists and user needs: an efficient interface between users and providers; an optimized methodology to handle user requests and a portal to facilitate access to data and elaborated products. We detail in the paper how these three tools can limit the intervention of experts, educate users, and lead to the production of useful information. This work provides the basis on which the ENES (European Network for Earth System Modelling) Portal Interface for the Climate Impact Communities is built.

  • 82. Deque, M
    et al.
    Jones, R G
    Wild, M
    Giorgi, F
    Christensen, J H
    Hassell, D C
    Vidale, P L
    Rockel, B
    Jacob, D
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    de Castro, M
    Kucharski, F
    van den Hurk, B
    Global high resolution versus Limited Area Model climate change projections over Europe: quantifying confidence level from PRUDENCE results2005Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 25, nr 6, s. 653-670Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Four high resolution atmospheric general circulation models (GCMs) have been integrated with the standard forcings of the PRUDENCE experiment: IPCC-SRES A2 radiative forcing and Hadley Centre sea surface temperature and sea-ice extent. The response over Europe, calculated as the difference between the 2071-2100 and the 1961-1990 means is compared with the same diagnostic obtained with nine Regional Climate Models (RCM) all driven by the Hadley Centre atmospheric GCM. The seasonal mean response for 2m temperature and precipitation is investigated. For temperature, GCMs and RCMs behave similarly, except that GCMs exhibit a larger spread. However, during summer, the spread of the RCMs-in particular in terms of precipitation-is larger than that of the GCMs. This indicates that the European summer climate is strongly controlled by parameterized physics and/or high-resolution processes. The temperature response is larger than the systematic error. The situation is different for precipitation. The model bias is twice as large as the climate response. The confidence in PRUDENCE results comes from the fact that the models have a similar response to the IPCC-SRES A2 forcing, whereas their systematic errors are more spread. In addition, GCM precipitation response is slightly but significantly different from that of the RCMs.

  • 83. Deque, M.
    et al.
    Rowell, D. P.
    Luethi, D.
    Giorgi, F.
    Christensen, J. H.
    Rockel, B.
    Jacob, D.
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    de Castro, M.
    van den Hurk, B.
    An intercomparison of regional climate simulations for Europe: assessing uncertainties in model projections2007Inngår i: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 81, s. 53-70Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ten regional climate models (RCM) have been integrated with the standard forcings of the PRUDENCE experiment: IPCC-SRES A2 radiative forcing and Hadley Centre boundary conditions. The response over Europe, calculated as the difference between the 2071 2100and the 1961-1990 means can be viewed as an expected value about which various uncertainties exist. Uncertainties are measured here by variance in eight sub-European boxes. Four sources of uncertainty can be evaluated with the material provided by the PRUDENCE project. Sampling uncertainty is due to the fact that the model climate is estimated as an average over a finite number of years (30). Model uncertainty is due to the fact that the models use different techniques to discretize the equations and to represent sub-grid effects. Radiative uncertainty is due to the fact that IPCC-SRES A2 is merely one hypothesis. Some RCMs have been run with another scenario of greenhouse gas concentration (IPCC-SRES B2). Boundary uncertainty is due to the fact that the regional models have been run under the constraint of the same global model. Some RCMs have been run with other boundary forcings. The contribution of the different sources varies according to the field, the region and the season, but the role of boundary forcing is generally greater than the role of the RCM, in particular for temperature. Maps of minimum expected 2m temperature and precipitation responses for the IPCC-A2 scenario show that, despite the above mentioned uncertainties, the signal from the PRUDENCE ensemble is significant.

  • 84.
    Devasthale, Abhay
    et al.
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Sedlar, Joseph
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Koenigk, Torben
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Fetzer, E. J.
    The thermodynamic state of the Arctic atmosphere observed by AIRS: comparisons during the record minimum sea ice extents of 2007 and 20122013Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, nr 15, s. 7441-7450Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The record sea ice minimum (SIM) extents observed during the summers of 2007 and 2012 in the Arctic are stark evidence of accelerated sea ice loss during the last decade. Improving our understanding of the Arctic atmosphere and accurate quantification of its characteristics becomes ever more crucial, not least to improve predictions of such extreme events in the future. In this context, the Atmospheric Infrared Sounder (AIRS) instrument onboard NASA's Aqua satellite provides crucial insights due to its ability to provide 3-D information on atmospheric thermodynamics. Here, we facilitate comparisons in the evolution of the thermodynamic state of the Arctic atmosphere during these two SIM events using a decade-long AIRS observational record (2003-2012). It is shown that the meteorological conditions during 2012 were not extreme, but three factors of preconditioning from winter through early summer played an important role in accelerating sea ice melt. First, the marginal sea ice zones along the central Eurasian and North Atlantic sectors remained warm throughout winter and early spring in 2012 preventing thicker ice build-up. Second, the circulation pattern favoured efficient sea ice transport out of the Arctic in the Atlantic sector during late spring and early summer in 2012 compared to 2007. Third, additional warming over the Canadian archipelago and southeast Beaufort Sea from May onward further contributed to accelerated sea ice melt. All these factors may have lead the already thin and declining sea ice cover to pass below the previous sea ice extent minimum of 2007. In sharp contrast to 2007, negative surface temperature anomalies and increased cloudiness were observed over the East Siberian and Chukchi seas in the summer of 2012. The results suggest that satellite-based monitoring of atmospheric preconditioning could be a critical source of information in predicting extreme sea ice melting events in the Arctic.

  • 85.
    Devasthale, Abhay
    et al.
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Tjernstrom, M.
    Caian, Mihaela
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Thomas, Manu Anna
    SMHI, Forskningsavdelningen, Luftmiljö.
    Kahn, B. H.
    Fetzer, E. J.
    Influence of the Arctic Oscillation on the vertical distribution of clouds as observed by the A-Train constellation of satellites2012Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, nr 21, s. 10535-10544Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main purpose of this study is to investigate the influence of the Arctic Oscillation (AO), the dominant mode of natural variability over the northerly high latitudes, on the spatial (horizontal and vertical) distribution of clouds in the Arctic. To that end, we use a suite of sensors on-board NASA's A-Train satellites that provide accurate observations of the distribution of clouds along with information on atmospheric thermodynamics. Data from three independent sensors are used (AQUA-AIRS, CALIOP-CALIPSO and CPR-CloudSat) covering two time periods (winter half years, November through March, of 2002-2011 and 2006-2011, respectively) along with data from the ERA-Interim reanalysis. We show that the zonal vertical distribution of cloud fraction anomalies averaged over 67-82 degrees N to a first approximation follows a dipole structure (referred to as "Greenland cloud dipole anomaly", GCDA), such that during the positive phase of the AO, positive and negative cloud anomalies are observed eastwards and westward of Greenland respectively, while the opposite is true for the negative phase of AO. By investigating the concurrent meteorological conditions (temperature, humidity and winds), we show that differences in the meridional energy and moisture transport during the positive and negative phases of the AO and the associated thermodynamics are responsible for the conditions that are conducive for the formation of this dipole structure. All three satellite sensors broadly observe this large-scale GCDA despite differences in their sensitivities, spatio-temporal and vertical resolutions, and the available lengths of data records, indicating the robustness of the results. The present study also provides a compelling case to carry out process-based evaluation of global and regional climate models.

  • 86.
    Devasthale, Abhay
    et al.
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Tjernstrom, Michael
    Karlsson, Karl-Göran
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Thomas, Manu Anna
    SMHI, Forskningsavdelningen, Luftmiljö.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Sedlar, Joseph
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Omar, Ali H.
    The vertical distribution of thin features over the Arctic analysed from CALIPSO observations2011Inngår i: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 63, nr 1, s. 77-85Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Clouds play a crucial role in the Arctic climate system. Therefore, it is essential to accurately and reliably quantify and understand cloud properties over the Arctic. It is also important to monitor and attribute changes in Arctic clouds. Here, we exploit the capability of the CALIPSO-CALIOP instrument and provide comprehensive statistics of tropospheric thin clouds, otherwise extremely difficult to monitor from passive satellite sensors. We use 4 yr of data (June 2006-May 2010) over the circumpolar Arctic, here defined as 67-82 degrees N, and characterize probability density functions of cloud base and top heights, geometrical thickness and zonal distribution of such cloud layers, separately for water and ice phases, and discuss seasonal variability of these properties. When computed for the entire study area, probability density functions of cloud base and top heights and geometrical thickness peak at 200-400, 1000-2000 and 400-800 m, respectively, for thin water clouds, while for ice clouds they peak at 6-8, 7-9 and 400-1000 m, respectively. In general, liquid clouds were often identified below 2 km during all seasons, whereas ice clouds were sensed throughout the majority of the upper troposphere and also, but to a smaller extent, below 2 km for all seasons.

  • 87.
    Devasthale, Abhay
    et al.
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Willén, Ulrika
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Karlsson, Karl-Göran
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Quantifying the clear-sky temperature inversion frequency and strength over the Arctic Ocean during summer and winter seasons from AIRS profiles2010Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, nr 12, s. 5565-5572Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Temperature inversions are one of the dominant features of the Arctic atmosphere and play a crucial role in various processes by controlling the transfer of mass and moisture fluxes through the lower troposphere. It is therefore essential that they are accurately quantified, monitored and simulated as realistically as possible over the Arctic regions. In the present study, the characteristics of inversions in terms of frequency and strength are quantified for the entire Arctic Ocean for summer and winter seasons of 2003 to 2008 using the AIRS data for the clear-sky conditions. The probability density functions (PDFs) of the inversion strength are also presented for every summer and winter month. Our analysis shows that although the inversion frequency along the coastal regions of Arctic decreases from June to August, inversions are still seen in almost each profile retrieved over the inner Arctic region. In winter, inversions are ubiquitous and are also present in every profile analysed over the inner Arctic region. When averaged over the entire study area (70 degrees N-90 degrees N), the inversion frequency in summer ranges from 69 to 86% for the ascending passes and 72-86% for the descending passes. For winter, the frequency values are 88-91% for the ascending passes and 89-92% for the descending passes of AIRS/AQUA. The PDFs of inversion strength for the summer months are narrow and right-skewed (or positively skewed), while in winter, they are much broader. In summer months, the mean values of inversion strength for the entire study area range from 2.5 to 3.9 K, while in winter, they range from 7.8 to 8.9 K. The standard deviation of the inversion strength is double in winter compared to summer. The inversions in the summer months of 2007 were very strong compared to other years. The warming in the troposphere of about 1.5-3.0K vertically extending up to 400 hPa was observed in the summer months of 2007.

  • 88.
    Dieterich, Christian
    et al.
    SMHI, Forskningsavdelningen, Oceanografi.
    Schimanke, Semjon
    SMHI, Forskningsavdelningen, Oceanografi.
    Wang, Shiyu
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Väli, Germo
    SMHI, Forskningsavdelningen, Oceanografi.
    Liu, Ye
    SMHI, Forskningsavdelningen, Oceanografi.
    Hordoir, Robinson
    SMHI, Forskningsavdelningen, Oceanografi.
    Höglund, Anders
    SMHI, Forskningsavdelningen, Oceanografi.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Evaluation of the SMHI coupled atmosphere-ice-ocean model RCA4-NEMO2013Rapport (Annet vitenskapelig)
    Abstract [sv]

    Den regionala kopplade atmosfär-is-havsmodellen RCA4-NEMO som utvecklats vid SMHI, utvärderas baserat på en ERA40-återanalys. Utvecklingen av den regionala klimatmodellen fortsätter men en första utvärdering presenteras här för att informera om aktuell status.RCA4-NEMO i aktuell status innehåller två modellkomponenter. Den regionala atmosfärsmodellen RCA4 täcker hela Europa och är tvåvägskopplad till en is-hav-modell för Nordsjön och Östersjön baserat på NEMO. Den används för tillfället för nedskalning av CMIP5-scenarier för detta århundrade för Nordsjön och Östersjön. Som en del av utvärderingen av RCA4-NEMO presenteras en analys och diskussion av hindcast-körning 1970-1999. Modellresulaten jämförs med observationsdata. Temperatur nära ytan och värmeflödet är förhållandevis bra vid en jämförelse med in-situ-mätningar och skattningar baserade på satellitdata. Salthalt och färskvattenutbyte är dock mindre bra. Momentumflödet från atmosfär till hav identifieras som en kritisk process i kopplingen mellan modellerna. Med undantag för färskvattensutbytet mellan atmosfär och hav är de klimatologiska egenskaperna nära ytan och motsvarande flöden jämförbara med klimatologiska observationer för perioden 1970-1999.

  • 89.
    Dieterich, Christian
    et al.
    SMHI, Forskningsavdelningen, Oceanografi.
    Wang, Shiyu
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Schimanke, Semjon
    SMHI, Forskningsavdelningen, Oceanografi.
    Groger, Matthias
    SMHI, Forskningsavdelningen, Oceanografi.
    Klein, Birgit
    Hordoir, Robinson
    SMHI, Forskningsavdelningen, Oceanografi.
    Samuelsson, Patrick
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Liu, Ye
    SMHI, Forskningsavdelningen, Oceanografi.
    Axell, Lars
    SMHI, Forskningsavdelningen, Oceanografi.
    Höglund, Anders
    SMHI, Forskningsavdelningen, Oceanografi.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Surface Heat Budget over the North Sea in Climate Change Simulations2019Inngår i: Atmosphere, ISSN 2073-4433, E-ISSN 2073-4433, Vol. 10, nr 5, artikkel-id 272Artikkel i tidsskrift (Fagfellevurdert)
  • 90.
    Doescher, Ralf
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Beckmann, A
    Effects of a bottom boundary layer parameterization in a coarse-resolution model of the North Atlantic Ocean2000Inngår i: Journal of Atmospheric and Oceanic Technology, ISSN 0739-0572, E-ISSN 1520-0426, Vol. 17, nr 5, s. 698-707Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The bottom boundary layer model approach of Beckmann and Doscher has been adopted for application in a coarse-resolution model of the North Atlantic Ocean. Both components of the approach (advective and conditional diffusive) are found to affect the deep water stratification and circulation. A significant deepening of the downward spreading North Atlantic Deep Water (NADW) is the major effect. This is associated with an enhanced spatial coverage of the NADW cell in the meridional circulation.

  • 91.
    Doescher, Ralf
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Hansson, Ulf
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Rutgersson, Anna
    Willén, Ulrika
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    The development of the coupled ocean-atmosphere model RCAO2001Inngår i: Third study conference on BALTEX / [ed] J. Meywerk, 2001, s. 45-46Konferansepaper (Annet vitenskapelig)
  • 92.
    Doescher, Ralf
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Koenigk, Torben
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Arctic rapid sea ice loss events in regional coupled climate scenario experiments2013Inngår i: Ocean Science, ISSN 1812-0784, E-ISSN 1812-0792, Vol. 9, nr 2, s. 217-248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rapid sea ice loss events (RILEs) in a mini-ensemble of regional Arctic coupled climate model scenario experiments are analyzed. Mechanisms of sudden ice loss are strongly related to atmospheric circulation conditions and preconditioning by sea ice thinning during the seasons and years before the event. Clustering of events in time suggests a strong control by large-scale atmospheric circulation. Anomalous atmospheric circulation is providing warm air anomalies of up to 5 K and is forcing ice flow, affecting winter ice growth. Even without a seasonal preconditioning during winter, ice drop events can be initiated by anomalous inflow of warm air during summer. It is shown that RILEs can be generated based on atmospheric circulation changes as a major driving force without major competing mechanisms, other than occasional longwave effects during spring and summer. Other anomalous seasonal radiative forcing or short-lived forcers (e.g., soot) play minor roles or no role at all in our model. RILEs initiated by ocean forcing do not occur in the model, although cannot be ruled out due to model limitations. Mechanisms found are qualitatively in line with observations of the 2007 RILE.

  • 93.
    Doescher, Ralf
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Simulated sea surface temperature and heat fluxes in different climates of the Baltic Sea2004Inngår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 33, nr 4-5, s. 242-248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The physical state of the Baltic Sea in possible future climates is approached by numerical model experiments with a regional coupled ocean-atmosphere model driven by different global simulations. Scenarios and recent climate simulations are compared to estimate changes. The sea surface is clearly warmer by 2.9degreesC in the ensemble mean. The horizontal pattern of average annual mean warming can largely be explained in terms of ice-cover reduction. The transfer of heat from the atmosphere to the Baltic Sea shows a changed seasonal cycle: a reduced heat loss in fall, increased heat uptake in spring, and reduced heat uptake in summer. The interannual variability of surface temperature is generally increased. This is associated with a smoothed frequency distribution in northern basins. The overall heat budget shows increased solar radiation to the sea surface, which is balanced by changes of the other heat flux components.

  • 94.
    Doescher, Ralf
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Simulated Sea Surface Temperature and Sea Ice in Different Climates of the Baltic2004Inngår i: Fourth Study Conference on BALTEX: Conference Proceedings / [ed] Hans-Jörg Isemer, Risø National Laboratory Technical University of Denmark GKSS Forschungszentrum Geesthacht GmbH , 2004, Vol. 4, s. 162-163Konferansepaper (Annet vitenskapelig)
  • 95.
    Doescher, Ralf
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Vihma, T.
    Maksimovich, E.
    Recent advances in understanding the Arctic climate system state and change from a sea ice perspective: a review2014Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 14, nr 24, s. 13571-13600Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sea ice is the central component and most sensitive indicator of the Arctic climate system. Both the depletion and areal decline of the Arctic sea ice cover, observed since the 1970s, have accelerated since the millennium. While the relationship of global warming to sea ice reduction is evident and underpinned statistically, it is the connecting mechanisms that are explored in detail in this review. Sea ice erodes both from the top and the bottom. Atmospheric, oceanic and sea ice processes interact in non-linear ways on various scales. Feedback mechanisms lead to an Arctic amplification of the global warming system: the amplification is both supported by the ice depletion and, at the same time, accelerates ice reduction. Knowledge of the mechanisms of sea ice decline grew during the 1990s and deepened when the acceleration became clear in the early 2000s. Record minimum summer sea ice extents in 2002, 2005, 2007 and 2012 provide additional information on the mechanisms. This article reviews recent progress in understanding the sea ice decline. Processes are revisited from atmospheric, oceanic and sea ice perspectives. There is strong evidence that decisive atmospheric changes are the major driver of sea ice change. Feedbacks due to reduced ice concentration, surface albedo, and ice thickness allow for additional local atmospheric and oceanic influences and self-supporting feedbacks. Large-scale ocean influences on Arctic Ocean hydrology and circulation are highly evident. Northward heat fluxes in the ocean are clearly impacting the ice margins, especially in the Atlantic sector of the Arctic. There is little indication of a direct and decisive influence of the warming ocean on the overall sea ice cover, due to an isolating layer of cold and fresh water underneath the sea ice.

  • 96.
    Doescher, Ralf
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Willen, Ulrika
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Rutgersson, Anna
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Hansson, Ulf
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Graham, Phil
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    The development of the regional coupled ocean-atmosphere model RCAO2002Inngår i: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 7, nr 3, s. 183-192Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A regional coupled ocean-atmosphere-ice general circulation model for northern Europe is introduced for climate study purposes. The Baltic Sea is interactively coupled. The coupled model is validated in a 5-year hind-cast experiment with a focus on surface quantities and atmosphere-ocean heat fluxes. The coupled sea surface temperature matches observations well. The system is free of drift, does not need flux corrections and is suitable for multi-year climate runs. With flux forcing from the atmospheric model the regional ocean model gives sea surface temperatures statistically equivalent to the uncoupled ocean model forced by observations. Other oceanic surface quantities do not reach this quality in combination with the current atmosphere model. A strong dependence of sea ice extent on details of the atmospheric radiation scheme is found. Our standard scheme leads to an overestimation of ice, most likely due to a negative bias of long-wave radiation. There is indication that a latent heat flux bias in fall contributes to the ice problem. Other atmosphere-ocean heat fluxes are generally realistic in the long term mean.

  • 97.
    Doescher, Ralf
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Wyser, Klaus
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Qian, Minwei
    Redler, Ren
    Quantifying Arctic contributions to climate predictability in a regional coupled ocean-ice-atmosphere model2010Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 34, nr 7-8, s. 1157-1176Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relative importance of regional processes inside the Arctic climate system and the large scale atmospheric circulation for Arctic interannual climate variability has been estimated with the help of a regional Arctic coupled ocean-ice-atmosphere model. The study focuses on sea ice and surface climate during the 1980s and 1990s. Simulations agree reasonably well with observations. Correlations between the winter North Atlantic Oscillation index and the summer Arctic sea ice thickness and summer sea ice extent are found. Spread of sea ice extent within an ensemble of model runs can be associated with a surface pressure gradient between the Nordic Seas and the Kara Sea. Trends in the sea ice thickness field are widely significant and can formally be attributed to large scale forcing outside the Arctic model domain. Concerning predictability, results indicate that the variability generated by the external forcing is more important in most regions than the internally generated variability. However, both are in the same order of magnitude. Local areas such as the Northern Greenland coast together with Fram Straits and parts of the Greenland Sea show a strong importance of internally generated variability, which is associated with wind direction variability due to interaction with atmospheric dynamics on the Greenland ice sheet. High predictability of sea ice extent is supported by north-easterly winds from the Arctic Ocean to Scandinavia.

  • 98. Doos, K
    et al.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Doescher, Ralf
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    The Baltic haline conveyor belt or the overturning circulation and mixing in the Baltic2004Inngår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 33, nr 4-5, s. 261-266Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A study of the water-mass circulation of the Baltic has been undertaken by making use of a three dimensional Baltic Sea model simulation. The saline water from the North Atlantic is traced through the Danish Sounds into the Baltic where it upwells and mixes with the fresh water inflow from the rivers forming a Baltic haline conveyor belt. The mixing of the saline water from the Great Belt and Oresund with the fresh water is investigated making use of overturning stream functions and Lagrangian trajectories. The overturning stream function was calculated as a function of four different vertical coordinates (depth, salinity, temperature and density) in order to understand the path of the water and where it upwells and mixes. Evidence of a fictive depth overturning cell similar to the Deacon Cell in the Southern Ocean was found in the Baltic proper corresponding to the gyre circulation around Gotland, which vanishes when the overturning stream function is projected on density layers. A Lagrangian trajectory study was performed to obtain a better view of the circulation and mixing of the saline and fresh waters. The residence time of the water masses in the Baltic is calculated to be 26-29 years and the Lagrangian dispersion reaches basin saturation after 5 years.

  • 99. Dosio, Alessandro
    et al.
    Mentaschi, Lorenzo
    Fischer, Erich M.
    Wyser, Klaus
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Extreme heat waves under 1.5 degrees C and 2 degrees C global warming2018Inngår i: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 13, nr 5, artikkel-id 054006Artikkel i tidsskrift (Fagfellevurdert)
  • 100.
    Eliasson, Salomon
    et al.
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Karlsson, Karl-Göran
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    van Meijgaard, Erik
    Meirink, Jan Fokke
    Stengel, Martin
    Willén, Ulrika
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    The Cloud_cci simulator v1.0 for the Cloud_cci climate data record and its application to a global and a regional climate model2019Inngår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 12, nr 2, s. 829-847Artikkel i tidsskrift (Fagfellevurdert)
1234567 51 - 100 of 496
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