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  • 1.
    Andersson, Tage
    SMHI, Research Department.
    VAD winds from C band Ericsson Doppler Weather Radars1998In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 7, no 6, p. 309-319Article in journal (Refereed)
    Abstract [en]

    The VAD (Velocity Azimuth Display) technique for retrieving winds from a single Doppler weather radar is well known as a robust and simple one, though still not used on its merits. Precipitation generally gives VAD winds, but it is less known that even in high latitudes during the warmer seasons the Doppler weather radars of today record enough clear air echos to give wind profiles in the planetary boundary layer. There are, however, few verifications of VAD winds in general, and hardly any concerning clear air. In this paper mainly VAD winds from one Ericsson Doppler Weather Radar in Jonsered, Gothenburg (57.723 degrees N, 12.172 degrees E, 164 m above MSL) are compared to Radiosonde Winds (RAWINDs) from Landwetter (57.668 degrees N, 12.296 degrees E, 155 m above MSL). The sites are about 10 km apart, and the radiosonde is within the range used for the VAD (30 km). The VAD soundings were made each hour, and the radiosoundings every 6th (00, 06, 12 and 18 UTC). About seven months of data were available (9 Dec. 1994 to 14 Feb. 1995 and 28 Jun. to 30 Nov. 1995). The LORAN C system was used to retrieve the RAWINDs during the first period (Dec. 1994 to Feb. 1995), and the OMEGA system was used during the second period. The comparisons are made using the five standard pressure levels, 925, 850, 700, 500 and 400 hPa, corresponding to heights above MSL of about 750, 1450, 3000, 5600 and 7200 m. As overall results, the average differences, in m/s, between the VAD and RAWIND were largest at the lowest (geometrically) levels, and higher up more or less constant with height. This is remarkable, since the wind speed increases with height, and the relative differences thus decrease with height. As an example, the average of the magnitude of the wind vector differences was 3.2 m/s at 925 hPa, but about 2.8 m/s at the higher levels. The differences also tend to be somewhat larger for winds retrieved from clear air echos. In the planetary boundary layer during summer, that is up to about 800 hPa, the availability of VAD winds was about 90 %. The availability decreases with height, and at 400 hPa it was 15 % for the whole period. Comparisons are also performed between VAD winds and winds from a limited area model, HIRLAM.

  • 2. Dersch, Juergen
    et al.
    Schroedter-Homscheidt, Marion
    Gairaa, Kacem
    Hanrieder, Natalie
    Landelius, Tomas
    SMHI, Research Department, Atmospheric remote sensing.
    Lindskog, Magnus
    SMHI, Research Department, Meteorology.
    Mueller, Stefan C.
    Santigosa, Lourdes Ramirez
    Sirch, Tobias
    Wilbert, Stefan
    Impact of DNI nowcasting on annual revenues of CSP plants for a time of delivery based feed in tariff2019In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 28, no 3, p. 235-253Article in journal (Refereed)
  • 3.
    Graham, Phil
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jacob, D
    Using large-scale hydrologic modeling to review runoff generation processes in GCM climate models2000In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 9, no 1, p. 49-57Article in journal (Refereed)
    Abstract [en]

    A large-scale application of the Swedish HBV hydrologic model was used to model the daily water balance of total runoff to the Baltic Sea. Ten-year present atmospheric climate model simulations from the ECHAM4/T106 global climate model were summarized on a runoff catchment basis. Climate model daily temperature and precipitation for the Baltic region were input to the water balance model for intercomparison runs. Comparison of results from the water balance model - with climate model input - to direct results from the climate model provides critical review of the behavior of the climate model. This: helped pinpoint systematic compensating errors in the land parameterization scheme.

  • 4. Helmert, Juergen
    et al.
    Lange, Martin
    Dong, Jiarui
    De Rosnay, Patricia
    Gustafsson, David
    SMHI, Research Department, Hydrology.
    Churulin, Evgeniy
    Kurzeneva, Ekaterina
    Mueller, Richard
    Trentmann, Joerg
    Souverijns, Niels
    Koch, Roland
    Boehm, Uwe
    Bartik, Martin
    Osuch, Marzena
    Rozinkina, Inna
    Bettems, Jean-Marie
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Marcucci, Francesca
    Milelli, Massimo
    1st Snow Data Assimilation Workshop in the framework of COST HarmoSnow ESSEM 14042018In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 27, no 4, p. 325-333Article in journal (Refereed)
  • 5.
    Karlsson, Karl-Göran
    SMHI, Research Department, Atmospheric remote sensing.
    Satellite sensing techniques and applications for the purpose of BALTEX2000In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 9, no 2, p. 111-116Article in journal (Refereed)
    Abstract [en]

    Various satellite sensing techniques and their corresponding applications suitable for use in validation and modelling activities in BALTEX are presented and discussed. Special emphasis is given to data and mature applications available during the main BALTEX BRIDGE experiment. For atmospheric simulations and studies, sensors measuring radiation budget quantities, cloud properties, moisture content and precipitation are considered as most important. Sensors measuring ice conditions and sea state parameters are identified for oceanographical applications and sensors measuring snow conditions and surface conditions are listed for hydrological studies. One example of an application based on extracted cloud information from NOAA AVHRR imagery is demonstrated. Estimations of mean cloud conditions in summer for the period 1991-1998 are shown for the total cloud cover, Cirrus cloudiness and low-level cloudiness over the Nordic region. It is shown that the Baltic Sea and other sea surfaces in the region has a large impact in suppressing summertime cloudiness, in particular low-level cloudiness. As a contrast, cloud patterns for high-level clouds show low correlation with the spatial distribution of sea surfaces. The influence of topographic features (i.e., the Scandinavian mountain range) seems more important here. Cirrus cloudiness peak on the lee side (to the east) of mountains suggesting a frequent presence of lee-wave cirrus clouds. As a summary, the following satellites and sensors will be the main satellite data sources for BALTEX: the ScaRaB instruments on the Ressurs and METEOR satellites, the CERES instrument on the EOS-AMI satellite, the AVHRR and ATOVS sensors on the NOAA satellites. the MVIRI and SEVIRI sensors on the METEOSAT satellites, the SAR instruments on the ERS, Radarsat and ENVISAT satellites and the SSM/I instrument on the DMSP satellites. Of particular interest is also radio occultation measurements of the radio signals from the GPS satellites. The need for a central BALTEX coordination facility (a satellite data function) with the objective to compile and transfer satellite data from various processing centres to BALTEX research groups is particularly stressed.

  • 6.
    Michelson, Daniel
    et al.
    SMHI, Core Services.
    Foltescu, Valentin
    SMHI.
    Häggmark, Lars
    SMHI, Core Services.
    Lindgren, Bo
    SMHI.
    MESAN Mesoscale analysis of precipitation2000In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 9, no 2, p. 85-96Article in journal (Refereed)
    Abstract [en]

    The Mesoscale Analysis System (MESAN) has been running operationally since April, 1997, providing science and consumers of weather information with spatially continuous fields of nine analysed meteorological parameters every hour. Data input to MESAN consists of surface observations from different observation systems, numerical weather prediction model fields, weather radar and satellite imageries, and climate information. Each data source is quality controlled before being subjected to an optimal interpolation (OI) scheme, together with data from the other sources. This paper presents MESAN's accumulated precipitation product. The methods used for interpolation of the multisource data are presented and discussed, as are the methods used to quality control each data source. Results from August-October 1995, using multisource data including gauge observations from the countries in the Baltic Sea Experiment (BALTEX) Region, exemplify the product. OI, used with a variable first guess error, has been compared with conventional inverse distance interpolation of precipitation in two catchments in mountainous terrain. Verification was conducted through modelled runoff, using areally integrated accumulated precipitation, compared with hydrograph observations. Significant improvements using OI were found in one of the catchments. The relative contribution (or importance) of each data source to the analysis has been evaluated using cross validation. Results show that gauge networks are the single most important sources and that radar imagery makes a significant contribution in areas lacking networks of dense gauges, such as the Baltic Sea. Analysis quality improves with the use of a greater number of input data sources. MESAN is an appropriate tool for creating an overall best estimate precipitation analysis and should be useful in applications where such information is required. In validating precipitation produced by numerical weather prediction models. analyses generated without the use of such model fields is recommended.

  • 7.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Rutgersson, Anna
    SMHI, Research Department, Climate research - Rossby Centre.
    Closing the water and heat cycles of the Baltic Sea2000In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 9, no 1, p. 59-66Article in journal (Refereed)
    Abstract [en]

    The objective of the present paper is to analyze the water and heat cycles of the Baltic Sea. The closure equations fur the water and heat cycles are formulated and the appropriate fluxes are calculated using the ocean model PROBE-Baltic forced by meteorological fields, river runoff and sea level data from the Kattegat. The time period considered is from November 1980 to November 1995. In the closing of the water cycle it is clear that river runoff, net precipitation (precipitation minus evaporation), in- and outflows through the Baltic Sea entrance area are the dominating flows. From the ocean model it is illustrated that the long-term water balance is consistent with the salinity in the Baltic Sea and that the net precipitation is positive during the studied period. For the closing of the heat cycle, the net heat loss to the atmosphere from the open water surface, as an annual moan, is in close balance with the solar radiation. The dominating fluxes in the net heat loss to the atmosphere are the sensible heat flux, the latent heat Aux and the net long wave radiation. The heat flux from water to ice also needs to be included in the modeling efforts. Heat flows associated with precipitation in the form of rain and snow can, as annual means, be neglected as well as the heat fluxes associated with river runoff, solar radiation through the ice and ice advecting out through the Baltic Sea entrance area. The total annual mean heat loss from the water body is in close balance with the annual change of heat storage in the water and the net heat exchange through the Baltic Sea entrance area is small. This illustrates that the Baltic Sea thermodynamically responds as a closed ocean basin.

  • 8.
    Rutgersson, Anna
    SMHI, Research Department, Climate research - Rossby Centre.
    A comparison between long term measured and modeled sensible heat and momentum fluxes using a High Resolution Limited Area Model (HIRLAM)2000In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 9, no 1, p. 31-39Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to study the surface fluxes obtained by a High Resolution Limited Area Model (HIRLAM), used for weather forecasts. The question arises whether the quality of the fluxes are high enough to make HIRLAM a proper tool for performing calculations of the water and energy budgets over the Baltic Sea, which is one of the aims of the BALTEX project. Turbulent fluxes modeled by HIRLAM are compared with direct flux measurements over sea for an extended time period. The model is shown to overestimate both sensible heat and momentum flux for the studied period. The sensible heat Aux for the studied period is overestimated by 8.1 W/m(2) and the momentum flux is systematically overestimated by 0.03 kg/ms(2) or 50 %. It is shown that the values of parameters in the surface parameterization scheme can be improved, for example will a lower value of the Charnock's coefficient agree better with the measurements. The sensitivity of the surface scheme to changes in mean parameters is studied. It is also shown that it is of great importance to have correct values of the near surface wind speed and the temperature difference between air and sea to obtain correct fluxes.

  • 9. Soerensson, Anna A.
    et al.
    Menendez, Claudio G.
    Ruscica, Romina
    Alexander, Peter
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Projected precipitation changes in South America: a dynamical downscaling within CLARIS2010In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 19, no 4, p. 347-355Article in journal (Refereed)
    Abstract [en]

    Responses of precipitation seasonal means and extremes over South America in a downscaling of a Climate change scenario are assessed with the Rossby Centre Regional Atmospheric Model (RCA). The anthropogenic warming under A1B scenario influences more on the likelihood of occurrence of severe extreme events like heavy precipitation and dry spells than on the mean seasonal precipitation. The risk of extreme precipitation increases in the La Plata Basin with a factor of 1.5-2.5 during all seasons and in the northwestern part of the continent with a factor 1.5-3 in summer, while it decreases in central and northeastern Brazil during winter and spring. The maximum amount of 5-days precipitation increases by up to 50% in La Plata Basin, indicating risks of flooding. Over central Brazil and the Bolivian lowland, where present 5-days precipitation is higher, the increases are similar in magnitude and could cause less impacts. In southern Amazonia, northeastern Brazil and the Amazon basin, the maximum number of consecutive dry days increases and mean winter and spring precipitation decreases, indicating a longer dry season. In the La Plata Basin, there is no clear pattern of change for the dry spell duration.

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