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  • 351.
    Bärring, Lars
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Persson, Gunn
    SMHI, Professional Services.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Evaluation of climate extremes in transient runs with the new Rossby Centre regional atmospheric model.2006In: Abstracts of the contributions of the EGU General Assembly 2006, EGU06-A-10110, 2006Conference paper (Other academic)
  • 352.
    Bärring, Lars
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    Does the projected pathway to global warming targets matter?2018In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 13, no 2, article id 024029Article in journal (Refereed)
  • 353.
    Bärring, Lars
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    von Storch, H
    Scandinavian storminess since about 18002004In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 31, no 20, article id L20202Article in journal (Refereed)
    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.

  • 354.
    Caian, Mihaela
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Devasthale, Abhay
    SMHI, Research Department, Atmospheric remote sensing.
    An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation2018In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, no 1-2, p. 423-441Article in journal (Refereed)
  • 355.
    Caian, Mihaela
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Devasthale, Abhay
    SMHI, Research Department, Atmospheric remote sensing.
    An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation (vol 50, pg 423, 2017)2018In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, no 1-2, p. 443-443Article in journal (Refereed)
  • 356. Campana, P. E.
    et al.
    Zhang, J.
    Yao, T.
    Andersson, Sandra
    SMHI, Core Services.
    Landelius, Tomas
    SMHI, Research Department, Atmospheric remote sensing.
    Melton, F.
    Yan, J.
    Managing agricultural drought in Sweden using a novel spatially-explicit model from the perspective of water-food-energy nexus2018In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 197, p. 1382-1393Article in journal (Refereed)
  • 357. Cardoso Pereira, Susana
    et al.
    Marta-Almeida, Martinho
    Carvalho, Ana
    SMHI, Research Department, Air quality.
    Heat wave and cold spell changes in Iberia for a future climate scenario2017In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088Article, review/survey (Refereed)
    Abstract [en]

    : This study investigates the impacts of climate change scenario on summer heat waves’ (HWs) and winter cold spells’ (CSs) characteristics for 12 locations over the Iberian Peninsula (IP). These characteristics are duration, recovery factor and intensity. Two future time slices of the chosen scenario are studied, namely, the periods 2046–2065 and 2081–2100 which are compared with a reference climate for the recent-past (1986–2005). The RCP8.5 greenhouse gas emission scenario is considered. The minimum and maximum daily temperature were obtained for these periods through regional model simulations using the Weather and Research Forecast (WRF) model forced with the MPI-ESM-LR model. The model was validated against EOBS and SPAIN02 datasets. The model shows 90th/10th percentile temperature (i.e. thresholds to identify HW/CS) biases. Therefore, HW/CS numbers and properties were evaluated using the model’s respective thresholds. HW/CS numbers and characteristics were also compared between the model and EOBS derived data. Probability density functions (PDFs) of the duration, recovery factor and intensity show significant changes in the mean and variance for the summer HWs. Differences, between future and recent-past climate in the extremes are evaluated by the 95th percentile which show an increase in the duration and intensity of the HWs for the future time slices. Very few CSs were detectable in the mid-term future (2046–2065) and none in the long-term future (2080–2100), except for Barcelona. For most locations, the CS for the future are of smaller duration and intensity. The PDF of the recovery factor suggests smaller absolute differences between the minimum and maximum temperature during winter which is also confirmed by the percentile analysis. The increase in the duration and intensity of HWs is greater in the long-term future than in the mid-term future, pointing for a warmer IP with more and longer HWs towards the end of the XXI century

  • 358.
    Carlberg, Stig
    SMHI, Research Department, Oceanography.
    Conservation of marine ecological quality - a current European perspective2005In: Aquatic conservation, ISSN 1052-7613, E-ISSN 1099-0755, Vol. 15, no 3, p. 211-214Article in journal (Other academic)
  • 359.
    Carlberg, Stig
    et al.
    SMHI, Core Services.
    Engström, Sven
    SMHI.
    Fonselius, Stig
    SMHI, Research Department, Oceanography.
    Palmén, Håkan
    SMHI.
    Fyrberg, Lotta
    SMHI, Core Services.
    Yhlén, Bengt
    SMHI.
    Szaron, Jan
    SMHI.
    Program för miljökvalitetsövervakning – PMK: Utsjöprogram under 19891990Report (Other academic)
  • 360.
    Carlberg, Stig
    et al.
    SMHI, Core Services.
    Engström, Sven
    SMHI.
    Fonselius, Stig
    SMHI, Research Department, Oceanography.
    Palmén, Håkan
    SMHI.
    Thelén, Eva-Gun
    SMHI.
    Fyrberg, Lotta
    SMHI, Core Services.
    Program för miljökvalitetsövervakning – PMK: Utsjöprogram under 19861987Report (Other academic)
  • 361.
    Carlberg, Stig
    et al.
    SMHI, Core Services.
    Engström, Sven
    SMHI.
    Fonselius, Stig
    SMHI, Research Department, Oceanography.
    Palmén, Håkan
    SMHI.
    Thelén, Eva-Gun
    SMHI.
    Fyrberg, Lotta
    SMHI, Core Services.
    Zagradkin, Danuta
    SMHI.
    Program för miljökvalitetsövervakning – PMK: Utsjöprogram under 19871988Report (Other academic)
  • 362.
    Carlberg, Stig
    et al.
    SMHI, Core Services.
    Engström, Sven
    SMHI.
    Fonselius, Stig
    SMHI, Research Department, Oceanography.
    Palmén, Håkan
    SMHI.
    Thelén, Eva-Gun
    SMHI.
    Fyrberg, Lotta
    SMHI, Core Services.
    Zagradkin, Danuta
    SMHI.
    Juhlin, Bo
    SMHI, Core Services.
    Szaron, Jan
    SMHI.
    Program för miljökvalitetsövervakning – PMK: Utsjöprogram under 19881989Report (Other academic)
  • 363.
    Carlberg, Stig
    et al.
    SMHI, Core Services.
    Engström, Sven
    SMHI.
    Fonselius, Stig
    SMHI, Research Department, Oceanography.
    Palmén, Håkan
    SMHI.
    Thelén, Eva-Gun
    SMHI.
    Thorstenson, Bodil
    SMHI.
    Program för miljökvalitetsövervakning – PMK1986Report (Other academic)
  • 364. Carlsen, Hanne Krage
    et al.
    Back, Erik
    Eneroth, Kristina
    Gislason, Thorarinn
    Holm, Mathias
    Janson, Christer
    Jensen, Steen Solvang
    Johannessen, Ane
    Kaasik, Marko
    Modig, Lars
    Segersson, David
    SMHI, Research Department, Air quality.
    Sigsgaard, Torben
    Forsberg, Bertil
    Olsson, David
    Orru, Hans
    Indicators of residential traffic exposure: Modelled NOX, traffic proximity, and self-reported exposure in RHINE III2017In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 167, p. 416-425Article in journal (Refereed)
  • 365.
    Carlsson, Bengt
    SMHI, Research Department, Hydrology.
    Alkalinitets- och pH-förändringar i Ume-älven orsakade av minimitappning1993Report (Other academic)
    Abstract [en]

    lnfluence of regulated minimum discharge on alkalinity and pH in river Umeälven At present the Swedish State Power Board is building a hydropower plant at Klippen in river Umeälven south of lake Överurnan. The plant is intended to be in operation <luring 1994. In connection with the start the discharge will be minimized at an about 10 km long river section between the outlet from Överurnan and Klippen. This interference will lead to a decrease of the alkalinity and pH values at the river section in question. In order to reduce the consequences as far as possible, minimum releases of 2. 0 m 3 /s from 1 J une to 15 September and 0. 5 m3 /s <luring the rest of the year have been suggested. Model simulations of pH and alk:alinity have been made for the period 1984- 91. The results show that the alk:alinity decreases from the lowest annual values of 0.05 - 0.06 mekv/1 to 0.02 - 0.03 mekv/1, which corresponds to a reduction of the pH values from 6.6 – 6 .7 to 6.2 - 6.3.

  • 366.
    Carlsson, Bengt
    SMHI, Research Department, Hydrology.
    Hydrokemiska data från de svenska fältforskningsområdena1985Report (Other academic)
    Abstract [sv]

    En viktig uppgift för SMHI är att övervaka och fortlöpande geupplysningar om hydrologiska data i Sverige. I och med övertagandet1979 av ansvaret för de av NFR upprättade FältForsknings~mrådena (FFO) har även hydrokemin kommit att utgöra ennaturlig del av SMHis verksamhetsområde.Denna rapport utgör en första publicering av de hydrokemiskadata med korresponderande vattenföringsdata, som idag, 1985,finns på SMHI i FFO-arkivet. Materialet presenteras här iform av tidsdiagram samt en tabell över de analyserade variablernasmedelvärden. Ytterligare en del äldre material frånIHD-områden finns fortfarande utspritt på andra institutionermen skall så småningom läggas in i FFO-arkivet. Rapporteninnehåller också en kortfattad beskrivning av varje område.Inga försök till utvärdering har gjorts. Dock har observeratsen viss skillnad i haltnivå för bl a Cl och N0 2 från IHDperioden1965-75 (analyserade av MISU) jämfört med perioden1979-84 (analyserade av SMHI). Orsaken skall utredas. Avsiktenär att på ett överskådligt sätt redovisa vilka data, somfinns tillgängliga för forskningsändamål.

  • 367.
    Carlsson, Bengt
    SMHI, Research Department, Hydrology.
    Some facts about the Torne and Kalix River Basins. A contribution to the NEWBALTIC II workshop in Abisko June 19991999Report (Other academic)
    Abstract [en]

    The Torne and Kalix rivers rise in the uppermost north west part of Sweden and their basins are situated between approximately 65°50N and 69°N as shown in Figure 1. The size basin of the two river basins is about 58 000 km2 of which 14 500 km2 (25%) is situated in Finland and 350 km 2 (0.6%) in Norway. The remaining, 43 150km2, makes up 9.7% of the area of Sweden. Data presented in this paper originate from Swedish measurements. Finnish data of snow and evaporation from the east of the Torne River basin can be find in the FinnishHydrological Yearbook (1994), which also includes some statistics for the period 1961-90.

    The density of population is very low, about three people per square kilometre. People are mostly living in the river valleys near the coast, the towns of Haparanda, Torneo and Kalix, or in ore-mining centres like Kiruna.

    Most of the basin can be characterised as a flat forest and mire area. The mountains in the north west part compose only 7-8 % of the total drainage basin. The runoff regime is thus characterised by a flow maximum produced by the snowmelt in the forest and swamp region. The mountains are very old. They were formed during the paleozoic era 300 000 000 years ago. As can be seen in Figure 3 at least 1/3 of the basin area is situated below 200masl andalso about 1/3 above the 500m elevation line.

    Topography is further described in Figure 3.

    As can be seen from Table I, the Torne River is number two and the Kalix River number 10 in drainage area order of the Swedish rivers. Due to dominating south-west winds and orographic effects, the Abisko region has a proportionately low precipitation. The specific runoff of the Torne River is thus lower then other Swedish rivers in this part of Sweden.

  • 368.
    Carlsson, Bengt
    et al.
    SMHI, Research Department, Hydrology.
    Bergström, Sten
    SMHI, Research Department, Hydrology.
    The TELFLOOD project: Rainfall – Runoff Modelling and forecasting1998Report (Other academic)
    Abstract [en]

    The aim of the TELFLOOD project is to improve methods for hydrological forecasting in steep

    catchments. The hydrological modelling task of SMHI has been to improve the HBV model and to

    develop and test routines for model updating and forecasting.

    A new response routine, based on the variable contributing area concept, has been developed and

    proved to be successful in several experimental basins in Sweden, Italy and Ireland

    . The technique

    uses the contributing area in a way that is consistent with the procedure for soil moisture accounting

    and does not require further free parameters. Model improvements are significant to the standard

    HBV-96 version, in particular as concems minor floods after dry periods.

    A new updating routine, based on state corrections of the storages of the HBV model, was

    developed and tested. For some events it proved to be more efficient than the standard method

    based on input corrections.

  • 369.
    Carlsson, Bengt
    et al.
    SMHI, Research Department, Hydrology.
    Bergström, Sten
    SMHI, Core Services.
    Andréasson, Johan
    SMHI, Professional Services.
    Hellström, Sara-Sofia
    SMHI, Core Services.
    Framtidens översvämningsrisker2006Report (Other academic)
    Abstract [en]

    A study of the impacts of global warming on future risks for floods and inundations in Sweden has been carried out on contract from Länsförsäkringsbolagens Forskningsfond. The work focussed on River Dalälven and the big lakes Vänern, Mälaren and Hjälmaren but some nationwide analyses were carried out as well. The methodology was based on two global climate models, two assumptions about the future emissions of greenhouse gases and a regional climate model for dynamical downscaling to Swedish conditions. The regional climate scenarios are further processed by the HBV hydrological model and the resulting river runoff or water levels are treated statistically by frequency analysis. The results show that future risk exposure is changing in a different way depending on location in the country. The situation seems to be aggravated in particular in the Vänern area in southwest Sweden and along its outlet, River Göta älv. There will also be increased risks in the western parts of the Scandinavian mountains. The risks for heavy rainfalls, which may cause severe local flooding are likely to increase even though it is difficult to discern a consistent regional pattern between the models, in this respect. The study has also addressed the uncertainty in the assessments of flood risks. It is obvious that uncertainties in the global climate scenarios are responsible for a lot of the uncertainty in the end results, but there are also uncertainties inflicted by the strategy used when transferring the climate change signal from climate models to the hydrological model.

  • 370.
    Carlsson, Bengt
    et al.
    SMHI, Research Department, Hydrology.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    HBV-modellen och flödesprognoser2001Report (Other academic)
    Abstract [sv]
    • Olika uppdateringsmetoder för HBV-modellen har utvecklats och jämförts. Metoderna har utvärderats i simuleringsexperiment där modellkörningar med observerade data användes som meteorologisk prognos. De olika uppdateringsmetoder som testats är dels autoregressiva, dvs de bygger på en korrektion av uppmätt fel före prognosens början, dels sådana som bygger på en uppdatering av indata dvs nederbörd och temperatur och slutligen sådana där modellens tillståndsvariabler uppdateras. Resultaten visar att alla metoderna medför en förbättrad avrinningsprognos. Ingen av metoderna kan dock sägas vara den bästa vid alla tillfällen. AR-metoden gav bäst resultat vid högsta flöden, t ex i samband med snösmältning, medan uppdatering av modellens tillstånd gav något bättre resultat vid regnflöden. Om en modell skall användas för prognoser i samband med höga flöden är det viktigt att man redan vid kalibreringen tar hänsyn till detta och kalibrerar med hänsyn till just toppflöden, som annars systematiskt kommer att underskattas.
    • Effekten av en uppdatering avklingar jämförelsevis snabbt. Vid långtidsprognoser är det troligt att en kombination av nu testade metoder och uppdatering av t ex snömagasin och de faktorer som speciellt påverkar snösmältningen, dvs. temperatur och kanske t o m modellens graddagfaktor, skulle ge en bättre prognos.
  • 371.
    Carlsson, Bengt
    et al.
    SMHI, Research Department, Hydrology.
    Sanner, Håkan
    SMHI, Core Services.
    Influence of river regulation on runoff to the Gulf of Bothnia: Gulf of Bothnia Year 19911994Report (Other academic)
  • 372.
    Carlsson, Bengt
    et al.
    SMHI, Research Department, Hydrology.
    Sanner, Håkan
    SMHI.
    Modelling influence of river regulation on runoff to the Gulf of Bothnia1996In: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 27, no 5, p. 337-350Article in journal (Refereed)
    Abstract [en]

    Runoff from a land area of approximately 490,000 km(2) enters the Gulf of Bothnia. This runoff is of essential importance for the flushing of the Gulf. a change in the volume of runoff effects the residence time. There are many natural as well as man made changes in the runoff, both in the form of long-term changes over many years and those occurring within one year. The most significant man made changes come from hydropower regulation. This report describes the effect on runoff from the development of the hydropower plants in Sweden and Finland by means of comparing recorded regulated runoff and simulated natural runoff. A recent time period, 1980-91, and a time period before regulation, 1925-36, were simulated. The monthly magnitudes of the redistributed flows were found to be on average 1,700 m(3)/s. The maximum redistributed monthly flow in May - June reached 5,000-6,000 m(3)/s.

  • 373.
    Carlund, Thomas
    SMHI, Core Services.
    Upgrade of SMHI's meteorological radiation network 2006-2007: Effects on direct and global solar radiation2011Report (Other academic)
    Abstract [en]

    The radiation network of SMHI was modernized in 2006-2007. Old measurements were closed down after 6-18 months of parallel operation of new and old measurements. This study reports the results of the comparison mainly between the old and new global and direct solar radiation measurements.On average the agreement between old and new measurements was good. The network average of ratios of whole period values was for global radiation 0.997 and for direct radiation 1.009. None of these results are significantly different from one at a level of confidence of 90 %.Despite the fairly good agreement some systematic differences between the old and new measurements were found. The differences are mainly thought to be caused by a difference in the apparent directional response between the old and new pyranometers and different viewing geometries in the old and new pyrheliometers. Functions to correct old global and direct radiation have been developed. These should be used to increase the homogeneity in Swedish solar radiation data from 1983and onwards, especially for monthly data.A new measurement method and new instruments for determination of sunshine duration were introduced in the upgraded network. A more detailed study comparing sunshine duration measurements by pyrheliometers in the old network and by contrast sensors in the modernized network, probably based on 1-minute or even instantaneous data, needs to be done in the future.

  • 374.
    Carlund, Thomas
    et al.
    SMHI, Core Services.
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    Land, P
    Aerosol optical depth over the Baltic Sea derived from AERONET and SeaWiFS measurements2005In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 26, no 2, p. 233-245Article in journal (Refereed)
    Abstract [en]

    Three years of data on aerosol optical depth (tau(a)) from the Aerosol Robotic Network (AERONET) station on the island of Gotland in the Baltic Sea have been analysed and compared with Sea-viewing Wide Field of view Sensor (SeaWiFS) data. Normally, the atmosphere over Gotland could be considered as clear, with a daily median value Of tau(a) at 500 nm of about 0.08. The median value of Angstrom's wavelength exponent (alpha) for wavelengths between 440 nm and 870 nm was 1.37, indicating that the dominant aerosol is more of a continental than of a pure maritime type. SeaWiFS GAC level 2 data on tau(a) and alpha were compared to data from the ground-based AERONET station. For the 37 cases of simultaneous satellite and ground-based measurements under cloud-free skies it was found that, on average, the value of tau(a)(865 nm) from SeaWiFS was about 0.02 higher than tau(a)(870 nm) from the AERONET station. At the same time approximate tau(a)(440 nm) from SeaWiFS was about 0.03 lower than tau(a)(440 nm) of AERONET. alpha(510, 865) from SeaWiFS was, on average, 1.2 lower than alpha(500, 870) from the AERONET measurements. These results cannot explain the very frequent occurences of negative values of normalized water-leaving radiance at 412 nm and 443 nm in the SeaWiFS reprocessing #3 data.

  • 375.
    Carlund, Thomas
    et al.
    SMHI, Core Services.
    Kouremeti, Natalia
    Kazadzis, Stelios
    Grobner, Julian
    Aerosol optical depth determination in the UV using a four-channel precision filter radiometer2017In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 10, no 3, p. 905-923Article in journal (Refereed)
  • 376.
    Carlund, Thomas
    et al.
    SMHI, Core Services.
    Landelius, Tomas
    SMHI, Research Department, Atmospheric remote sensing.
    Josefsson, Weine
    SMHI, Research Department, Atmospheric remote sensing.
    Comparison and uncertainty of aerosol optical depth estimates derived from spectral and broadband measurements2003In: Journal of applied meteorology (1988), ISSN 0894-8763, E-ISSN 1520-0450, Vol. 42, no 11, p. 1598-1610Article in journal (Refereed)
    Abstract [en]

    An experimental comparison of spectral aerosol optical depth tau(a,lambda) derived from measurements by two spectral radiometers [a LI-COR, Inc., LI-1800 spectroradiometer and a Centre Suisse d'Electronique et de Microtechnique (CSEM) SPM2000 sun photometer] and a broadband field pyrheliometer has been made. The study was limited to three wavelengths ( 368, 500, and 778 nm), using operational calibration and optical depth calculation procedures. For measurements taken on 32 days spread over 1 yr, the rms difference in tau(a,lambda) derived from the two spectral radiometers was less than 0.01 at 500 and 778 nm. For wavelengths shorter than 500 nm and longer than 950 nm, the performance of the LI-1800 in its current configuration did not permit accurate determinations of tau(a,lambda). Estimates of spectral aerosol optical depth from broadband pyrheliometer measurements using two models of the Angstromngstrom turbidity coefficient were examined. For the broadband method that was closest to the sun photometer results, the mean (rms) differences in tau(a,lambda) were 0.014 (0.028), 0.014 (0.019), and 0.013 ( 0.014) at 368, 500, and 778 nm. The mean differences are just above the average uncertainties of the sun photometer tau(a,lambda) values (0.012, 0.011, and 0.011) for the same wavelengths, as determined through a detailed uncertainty analysis. The amount of atmospheric water vapor is a necessary input to the broadband methods. If upper-air sounding data are not available, water vapor from a meteorological forecast model yields significantly better turbidity results than does using estimates from surface measurements of air temperature and relative humidity.

  • 377. Carmichael, G R
    et al.
    Calori, G
    Hayami, H
    Uno, I
    Cho, S Y
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Kim, S B
    Ichikawa, Y
    Ikeda, Y
    Woo, J H
    Ueda, H
    Amann, M
    The MICS-Asia study: model intercomparison of long-range transport and sulfur deposition in East Asia2002In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 36, no 2, p. 175-199Article in journal (Refereed)
    Abstract [en]

    An intercomparison study involving eight long-range transport models for sulfur deposition in East Asia has been initiated, The participating models included Eulerian and Lagrangian frameworks, with a wide variety of vertical resolutions and numerical approaches. Results from this study, in which models used common data sets for emissions, meteorology, and dry, wet and chemical conversion rates, are reported and discussed. Model results for sulfur dioxide and sulfate concentrations, wet deposition amounts, for the period January and May 1993, are compared with observed quantities at 18 surface sites in East Asia. At many sites the ensemble of models is found to have high skill in predicting observed quantities. At other sites all models show poor predictive capabilities. Source-receptor relationships estimated by the models are also compared. The models show a high degree of consistency in identifying the main source-receptor relationships, as well as in the relative contributions of wet/dry pathways for removal. But at some locations estimated deposition amounts can vary by a factor or 5. The influence of model structure and parameters on model performance is discussed. The main factors determining the deposition fields are the emissions and underlying meteorological fields. Model structure in terms of vertical resolution is found to be more important than the parameterizations used for chemical conversion and removal, as these processes are highly coupled and often work in compensating directions. (C) 2002 Elsevier Science Ltd. All rights reserved.

  • 378. Carmichael, G R
    et al.
    Hayami, H
    Calori, G
    Uno, I
    Cho, S Y
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Kim, S B
    Ichikawa, Y
    Ikeda, Y
    Ueda, H
    Amann, M
    Model intercomparison study of long range transport and sulfur deposition in East Asia (MICS-ASIA)2001In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 130, no 1-4, p. 51-62Article in journal (Refereed)
    Abstract [en]

    To help improve the use of models in science & policy analysis in Asia it is necessary to have a better understanding of model performance and uncertainties. Towards this goal an intercomparison exercise has been initiated as a collaborative study of scientists interested in long-range transport in East Asia. An overview of this study is presented in this paper. The study consists of a set of prescribed test calculations with carefully controlled experiments. Models used the same domain, emission inventory, model parameters, meteorological conditions, etc. Two periods (January and May 1993) were selected to reflect long-range transport conditions under two distinct seasons. During these periods measurements of sulfur concentrations and deposition were made throughout the study region using identical sampling and analysis protocols. The intercomparison activity consists of four tasks (Blind Test, Fixed Parameter Test, Source Receptor test, and Tuning Test). All participants were asked to do Task A, and as many of the other tasks as possible. To date seven different models have participated in this study. Results and key findings are presented.

  • 379. Carmichael, G. R.
    et al.
    Sakurai, T.
    Streets, D.
    Hozumi, Y.
    Ueda, H.
    Park, S. U.
    Fung, C.
    Han, Z.
    Kajino, M.
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Bennet, Cecilia
    SMHI, Research Department, Air quality.
    Hayami, H.
    Sartelet, K.
    Holloway, T.
    Wang, Z.
    Kannari, A.
    Fu, J.
    Matsuda, K.
    Thongbooncho, N.
    Amann, M.
    MICS-Asia II: The model intercomparison study for Asia Phase II methodology and overview of findings2008In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 42, no 15, p. 3468-3490Article, review/survey (Refereed)
    Abstract [en]

    Results from the Model Intercomparison Study Asia Phase II (MICS-Asia II) are presented. Nine different regional modeling groups simulated chemistry and transport of ozone (O-3), secondary aerosol, acid deposition, and associated precursors, using common emissions and boundary conditions derived from a global model. Four-month-long periods, representing 2 years and three seasons (i.e., March, July, and December in 2001, and March in 2002), are analyzed. New observational data, obtained under the EANET (the Acid Deposition Monitoring Network in East Asia) monitoring program, were made available for this study, and these data provide a regional database to compare with model simulations. The analysis focused around seven subject areas: O-3 and related precursors, aerosols, acid deposition, global inflow of pollutants and precursor to Asia, model sensitivities to aerosol parameterization, analysis of emission fields, and detailed analyses of individual models, each of which is presented in a companion paper in this issue of Atmospheric Environment. This overview discusses the major findings of the study, as well as information on common emissions, meteorological conditions, and observations. (C) 2007 Elsevier Ltd. All rights reserved.

  • 380.
    Caron, Louis-Philippe
    et al.
    SMHI, Research Department, Climate research - 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 oscillation2015In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 44, no 7-8, p. 1801-1821Article in journal (Refereed)
    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.

  • 381. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Analysing present, past and future tropical cyclone activity as inferred from an ensemble of Coupled Global Climate Models2008In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 60, no 1, p. 80-96Article in journal (Refereed)
  • 382. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Research Department, Climate research - 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 conditions2012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, no 1-2, p. 113-135Article in journal (Refereed)
    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.

  • 383. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Doblas-Reyes, Francisco
    Multi-year prediction skill of Atlantic hurricane activity in CMIP5 decadal hindcasts2014In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 42, no 9-10, p. 2675-2690Article in journal (Refereed)
    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.

  • 384.
    Caron, Louis-Philippe
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - 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 model2013In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 40, no 5-6, p. 1257-1269Article in journal (Refereed)
    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.

  • 385.
    Caron, Louis-Philippe
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Winger, Katja
    Impact of resolution and downscaling technique in simulating recent Atlantic tropical cylone activity2011In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 37, no 5-6, p. 869-892Article in journal (Refereed)
    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.

  • 386. 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, Research Department, Climate research - Rossby Centre.
    Sanchez, E.
    Zaninelli, P.
    Performance of a multi-RCM ensemble for South Eastern South America2012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, no 12, p. 2747-2768Article in journal (Refereed)
    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.

  • 387. 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, Research Department, Climate research - Rossby Centre.
    Teichmann, C.
    Vautard, R.
    Daily precipitation statistics in a EURO-CORDEX RCM ensemble: added value of raw and bias-corrected high-resolution simulations2016In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 47, no 3-4, p. 719-737Article in journal (Refereed)
  • 388. Casini, Michele
    et al.
    Kall, Filip
    Hansson, Martin
    SMHI, Core Services.
    Plikshs, Maris
    Baranova, Tatjana
    Karlsson, Olle
    Lundstrom, Karl
    Neuenfeldt, Stefan
    Gardmark, Anna
    Hjelm, Joakim
    Hypoxic areas, density-dependence and food limitation drive the body condition of a heavily exploited marine fish predator2016In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 3, no 10, article id 160416Article in journal (Refereed)
  • 389.
    Cato, Ingemar
    et al.
    Geological Survey of Sweden (SGU),.
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    Hallberg, Ola
    Geological Survey of Sweden (SGU),.
    Kjellin, Bernt
    Geological Survey of Sweden (SGU),.
    Andersson, Pia
    SMHI, Core Services.
    Erlandsson, Cecilia
    Geological Survey of Sweden (SGU),.
    Axe, Philip
    SMHI, Research Department, Oceanography.
    A new approach to state the areas of oxygen deficits in the Baltic Sea2008Report (Other academic)
    Abstract [en]

    Sediment and near bottom water oxygen data was evaluated to look for correspondence in anoxic conditions. The SGU and SMHI monitoring data showed high correlation, although the actual data tested proved to be few, coincidence in space was promising. The conclusion drawn from the evaluation is that anoxic postglacial sediments were generally overlaid by near bottom anoxic waters. Hence, it is suggested that the spatial distribution of postglacial clays in the sea-bottom surface can be used, together with near bottom waters oxygen data, to improve spatial distribution in mapping oxygen deficits.Time series of oxygen deficit volume and area was calculated from near bottom data from several sub basins in the southern and central Baltic Proper. In general, hypoxic and anoxic water conditions increased over time but perturbations of improved oxygen conditions linked to major inflow events occurs especially in the Bornholm, Eastern and Western Gotland Basins.The high spatial variability of the postglacial sediments in the Western Gotland Basin compared to other basins indicates that it is indeed sensitive to the area coverage of anoxic waters. In addition, the relatively weak stratification and high variability over time of oxygen deficit make this basin favourable for oxygen improvement engineering methods.In coastal waters several bays along the Östergötland and Småland archipelagos should be further evaluated before selected for ecological engineering methods to improve oxygen conditions.

  • 390. Cavazos, Tereza
    et al.
    Luna-Nino, Rosa
    Cerezo-Mota, Ruth
    Fuentes Franco, Ramon
    SMHI, Research Department, Climate research - 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) domain2019In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088Article in journal (Refereed)
    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.

  • 391. Cederwall, K
    et al.
    Brandt, Maja
    SMHI, Research Department, Hydrology.
    Workshop 6 (synthesis): linking between flood risks and land use changes2002In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 45, no 8, p. 181-182Article in journal (Refereed)
    Abstract [en]

    Land use changes, such as deforestation, are increasing the world's vulnerability to flooding. Detailed knowledge of the local situation is essential for risk assessment and design of effective flood prevention measures and governs the infrastructure and engineering measures implemented. However extreme floods in large catchments can overwhelm both natural capacity and constructed flood management measures.

  • 392. Ceola, S.
    et al.
    Arheimer, Berit
    SMHI, Research Department, Hydrology.
    Baratti, E.
    Bloeschl, G.
    Capell, Réne
    SMHI, Research Department, Hydrology.
    Castellarin, A.
    Freer, J.
    Han, D.
    Hrachowitz, M.
    Hundecha, Yeshewatesfa
    SMHI, Research Department, Hydrology.
    Hutton, C.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Montanari, A.
    Nijzink, R.
    Parajka, J.
    Toth, E.
    Viglione, A.
    Wagener, T.
    Virtual laboratories: new opportunities for collaborative water science2015In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, no 4, p. 2101-2117Article in journal (Refereed)
    Abstract [en]

    Reproducibility and repeatability of experiments are the fundamental prerequisites that allow researchers to validate results and share hydrological knowledge, experience and expertise in the light of global water management problems. Virtual laboratories offer new opportunities to enable these prerequisites since they allow experimenters to share data, tools and pre-defined experimental procedures (i.e. protocols). Here we present the outcomes of a first collaborative numerical experiment undertaken by five different international research groups in a virtual laboratory to address the key issues of reproducibility and repeatability. Moving from the definition of accurate and detailed experimental protocols, a rainfall-runoff model was independently applied to 15 European catchments by the research groups and model results were collectively examined through a web-based discussion. We found that a detailed modelling protocol was crucial to ensure the comparability and reproducibility of the proposed experiment across groups. Our results suggest that sharing comprehensive and precise protocols and running the experiments within a controlled environment (e.g. virtual laboratory) is as fundamental as sharing data and tools for ensuring experiment repeatability and reproducibility across the broad scientific community and thus advancing hydrology in a more coherent way.

  • 393. Cerezo-Mota, Ruth
    et al.
    Cavazos, Tereza
    Arritt, Raymond
    Torres-Alavez, Abraham
    Sieck, Kevin
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Moufouma-Okia, Wilfram
    Antonio Salinas-Prieto, Jose
    CORDEX-NA: factors inducing dry/wet years on the North American Monsoon region2016In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 36, no 2, p. 824-836Article in journal (Refereed)
    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.

  • 394. Chadwick, R.
    et al.
    Martin, G. M.
    Copsey, D.
    Bellon, G.
    Caian, Mihaela
    SMHI, Research Department, Climate research - Rossby Centre.
    Codron, F.
    Rio, C.
    Roehrig, R.
    Examining the West African Monsoon circulation response to atmospheric heating in a GCM dynamical core2017In: Journal of Advances in Modeling Earth Systems, ISSN 1942-2466, Vol. 9, no 1, p. 149-167Article in journal (Refereed)
  • 395.
    Chen, Deliang
    et al.
    Göteborgs universitet.
    Johansson, Barbro
    SMHI, Professional Services.
    Temperaturens höjdberoende: En studie i Indalsälvens avrinningsområde2003Report (Other academic)
    Abstract [sv]

    Vid modellering av snösmältning och snöackumulation är temperaturen en viktig variabel. De lokala variationerna i temperaturen styrs till stor del av höjden över havet. Denna rapport redovisar ett projekt som haft till syfte att förbättra beskrivningen av temperaturens höjdberoende i de indata som används för att simulera avrinning med HBV-modellen. Studien har omfattat de övre delarna av Indalsälvens avrinningsområde. För att analysera variationerna i höjdberoendet prövades två angreppssätt:- En statistisk analys av observerade data vid de meteorologiska stationerna.- Simuleringar med en högupplöst meteorologisk modell.Syftet med att använda en meteorologisk modell var att den ger en mer komplett bild av temperaturvariationerna än stationerna som bara representerar en liten del av området.Den statistiska analysen av stationsdata visade en årstidsvariation i temperaturens höjdberoende. Snabbast avtog temperaturen med höjden under försommaren, medan man i snitt hade en svag ökning av temperaturen med höjden runt årskiftet. Studien visade också ett tydligt samband mellan temperatur och höjdberoende, vilket innebar att säsongsvariationen delvis förklarades av temperaturens årscykel. Under senvåren då en stor del av snösmältningen sker, låg temperaturavtagandet i snitt mycket nära 0.6oC/100m.Testerna med den meteorologiska modellen indikerade att det är ett angreppssätt som kan användas för att i detalj beskriva temperaturens variationer i ett område med komplex topografi, men att mer djupgående studier krävs för att fullt ut tolka modellresultaten. Generellt var höjdberoendet i modellen betydligt flackare än det som togs fram från stationsdata.Ur stationsdata togs ett enkelt samband fram för att beskriva temperaturens höjdberoende som en funktion av temperatur och tid på året. Sambandet användes sedan vid interpolation av temperatur och för simuleringar i HBV-modellen. En korsvalidering med stationsdata visade att ett variabelt höjdberoende gav en bättre skattning av temperaturen än ett konstant höjdavtagande. Förbättringen var störst under vintermånaderna och för högt belägna stationer.Trots att korsvalideringen visade bättre resultat med ett variabelt höjdberoende, blev det inga förbättringar av den simulerade avrinningen i HBV-modellen. Beskrivningen av höjdberoendet påverkade dock snöns fördelning i modellen. Även om det inte direkt har effekt på den simulerade avrinningen, så får det därför betydelse om man exempelvis vill uppdatera simulerat snömagasin från observationer.Slutsatsen från studien är att det idag inte finns skäl att ändra beskrivningen av temperaturens höjdberoende i HBV-modellen. Däremot bör modellen hållas öppen för ett variabelt höjdberoende i framtiden då nya typer av indata och uppdatering av snömagasinet kan bli aktuellt. Det samband som tagits fram för höjdberoendet är lätt att applicera och ger en bättre skattning av temperaturen än ett konstant höjdberoende.

  • 396. Chen, Hans W.
    et al.
    Zhang, Qiong
    Körnich, Heiner
    SMHI, Research Department, Meteorology.
    Chen, Deliang
    A robust mode of climate variability in the Arctic: The Barents Oscillation2013In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, no 11, p. 2856-2861Article in journal (Refereed)
    Abstract [en]

    The Barents Oscillation (BO) is an anomalous wintertime atmospheric circulation pattern in the Northern Hemisphere that has been linked to the meridional flow over the Nordic Seas. There are speculations that the BO has important implications for the Arctic climate; however, it has also been suggested that the pattern is an artifact of Empirical Orthogonal Function (EOF) analysis due to an eastward shift of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO). In this study, EOF analyses are performed to show that a robust pattern resembling the BO can be found during different time periods, even when the AO/NAO is relatively stationary. This BO has a high and stable temporal correlation with the geostrophic zonal wind over the Barents Sea, while the contribution from the AO/NAO is small. The surface air temperature anomalies over the Barents Sea are closely associated with this mode of climate variability.

  • 397. Cheymol, Anne
    et al.
    De Backer, Hugo
    Josefsson, Weine
    SMHI, Research Department, Atmospheric remote sensing.
    Stuebi, Rene
    Comparison and validation of the aerosol optical depth obtained with the Langley plot method in the UV-B from Brewer Ozone Spectrophotometer measurements2006In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 111, no D16, article id D16202Article in journal (Refereed)
    Abstract [en]

    [ 1] The Aerosol Optical Depths (AODs) retrieved from Brewer Ozone Spectrophotometer measurements with a method previously developed (Cheymol and De Backer, 2003) are now validated by comparisons between AODs from six Brewer spectrophotometers and two CSEM SPM2000 sunphotometers: two Brewer spectrophotometers 016 and 178 at Uccle in Belgium; one Brewer spectrophotometer 128 and one sunphotometer CSEM SPM2000 at Norrkoping in Sweden; and three Brewer instruments 040, 072, 156 at Arosa and one CSEM SPM2000 sunphotometer at Davos in Switzerland. The comparison between AODs from Brewer spectrophotometer 128 at 320.1 nm and sunphotometer SPM2000 at 368 nm at Norrkoping shows that the AODs obtained from the Brewer measurements with the Langley Plot Method (LPM) are very accurate if the neutral density filter spectral transmittances are well known: with the measured values of these filters, the correlation coefficient, the slope, and the intercept of the regression line are 0.98, 0.85 +/- 0.004, and 0.02 +/- 0.0014, respectively. The bias observed is mainly owing to the wavelength difference between the two instruments. The comparison between AODs from different Brewer spectrophotometers confirm that AODs will be in very good agreement if they are measured with several Brewer instruments at the same place: At Uccle, the correlation coefficient, slope, and intercept of the regression line are 0.98, 1.02 +/- 0.003, and 0.06 +/- 0.001, respectively; at Arosa, the comparisons between the AODs from three Brewer spectrophotometers 040, 072, and 156 give a correlation coefficient, a slope, and an intercept of the regression line above 0.94, 0.98 and below 0.04, respectively.

  • 398. Christensen, J H
    et al.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    Iversen, T
    Bjorge, D
    Christensen, O B
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    A synthesis of regional climate change simulations - A Scandinavian perspective2001In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 28, no 6, p. 1003-1006Article in journal (Refereed)
    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.

  • 399. Christensen, Jens H.
    et al.
    Carter, Timothy R.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Amanatidis, Georgios
    Evaluating the performance and utility of regional climate models: the PRUDENCE project2007In: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 81, p. 1-6Article in journal (Other academic)
    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.

  • 400. Christensen, Jens Hesselbjerg
    et al.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Giorgi, Filippo
    Lenderink, Geert
    Rummukainen, Markku
    SMHI, Core Services.
    Weight assignment in regional climate models2010In: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 44, no 2-3, p. 179-194Article in journal (Refereed)
    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.

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