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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 38 (1994), S. 316-324 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary The initialization and assimilation of input data were studied and tested by the adiabatic version of a simple numerical model for short-range weather forecast. The initialization was based on the utilization of a digital filter technique. The method succeeded in removing high-frequency oscillations from prognostic pressure fields. However, excessive smoothing deteriorated the accuracy of the prediction at the lowest levels of the atmosphere. The data assimilation was performed using the nudging method. Three versions of the nudging method in a splitting scheme were tested. The inclusion of the assimilation at the end of the integration step proved to be the best. The assimilation damped the oscillations of prognostic surface pressure fields and slightly improved the pressure prediction at the lowest levels of the atmosphere.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 39 (1995), S. 60-73 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary The relationship between information, contained in aerological data from the European area, and a thunderstorm occurrence in the area of the Czech Republic was investigated with input data from the period of May–September 1989–1991. SYNOP reports from Czech ground stations were utilized to assess event occurrence. TEMP 00UTC and TEMP 12UTC reports from European stations were used to determine potential diagnostic predictors, and the TEMP00 data served as the input data set for the 12hr mesoscale model forecast to gain prognostic predictors. Each of the two diagnostic data sets from 00UTC and 12UTC and of the prognostic data set comprised about 400 predictors/predictand elements. The categorical forecast of thunderstorm occurrence, based on the application of linear regression and a simple version of pattern recognition, is discussed. The critical success index was determined for every type of forecast and used to assess forecast skill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 39 (1995), S. 74-83 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary A series of Helmholtz equations has to be solved in short-range weather forecast models which use a splitting scheme of integration. For these purposes the successive overrelaxation, the Gauss-Seidel relaxation, the conjugate gradient method, the steepest descent method, the full-multigrid method and the direct method based on the minimum degree algorithm were used and their efficiencies were compared. It was found that the full-multigrid method was the most efficient among the iterative methods in terms of computational time, and that the effect rapidly increased with the grid size. The direct method may be an appropriate approach if the solution is repeated for various right-hand sides, but it requires large auxiliary computer memory. The selection of the optimum method depends on the concrete problem being solved and on the computer memory available.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 40 (1996), S. 178-186 
    ISSN: 1573-1626
    Keywords: Convection ; categorical forecasting ; statistical forecasting techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary Predictor vectors, including upper air as well as surface data, were used for categorical forecasting convective events over a subregion of the Czech territory, and the effect of including surface variables in the predictor vector was examined. While upper air data were considered as Perfect Prognosis, the surface data were successively included according to the time of their origin. The forecasting technique was based on linear multiple regression with learning, and the accuracy of the forecast was measured by the Critical Success Index. The input data from the three May-September periods in 1989–91 were used, and the first year served as the learning set. The aerological data from TEMP 12 UTC, simulating Perfect Prognosis, were the source of the upper air predictors. The performance of all, upper air, surface and combined, predictors were evaluated and compared. It turned out that the improvement of prediction accuracy due to the inclusion of surface variables was not negligible. Significant improvements were made in the forecasts of thunderstorm occurrence between 18 and 24 UTC.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 38-56 
    ISSN: 1573-1626
    Keywords: Statistical postprocessing ; Precipitation forecast ; NWP model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract Several statistical postprocessing methods are applied to results from a numerical weather prediction (NWP) model to test the potential for increasing the accuracy of its local precipitation forecasts. Categorical (Yes/No) forecasts for 12hr precipitation sums equalling or exceeding 0.1, 2.0 and 5.0 mm are selected for improvement. The two 12hr periods 0600-1800 UTC and 1800-0600 UTC are treated separately based on NWP model initial times 0000 UTC and 1200 UTC, respectively. Input data are taken from three successive summer seasons, April-September, 1994-96. The forecasts are prepared and verified for five synoptic stations, four located in the western Czech Republic, and one in Germany near the Czech-German border. Two approaches to statistical postprocessing are tested. The first uses Model Output Statistics (MOS) and the second modifies the MOS approach by applying a successive learning technique (SLT). For each approach several statistical models for the relationship between NWP model predictors and predictand were studied. An independent data set is used for forecast verification with the skill measured by a True Skill Score. The results of the statistical postprocessing are compared with the direct model precipitation forecasts from gridpoints nearest the stations, and they show that both postprocessing approaches provide substantially better forecasts than the direct NWP model output. The relative improvement increases with increasing precipitation amount and there is no significant difference in performance between the two 12hr periods. The skill of the SLT does not depend significantly on the size of the initial learning sample, but its results are nevertheless comparable with the results obtained from the MOS approach, which requires larger developmental samples.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2020-07-03
    Description: The distribution of hydrometeors in thunderstorms is still under investigation as well as the process of electrification in thunderclouds leading to lightning discharges. One indicator of cloud electrification might be high values of the Linear Depolarization Ratio (LDR) at higher vertical levels. This study focuses on LDR values derived from vertically pointing cloud radars and the distribution of five hydrometeor species during 38 days with thunderstorms which occurred in 2018 and 2019 in Central Europe, close to our radar site. The study shows improved algorithms for de-aliasing, the derivation of vertical air velocity and the classification of hydrometeors in clouds using radar data. The comparison of vertical profiles with observed lightning discharges in the vicinity of the radar site (≤1 km) suggested that cloud radar data can indirectly identify “lightning” areas by high LDR values observed at higher gates due to the alignment of ice crystals, likely because of an intensified electric field in thunderclouds. Simultaneously, the results indicated that at higher gates, there is a mixture of several hydrometeor species, which suggests a well-known electrification process by collisions of hydrometeors.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
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  • 7
    Publication Date: 2016-11-01
    Print ISSN: 0167-6105
    Electronic ISSN: 1872-8189
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Elsevier
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  • 8
    Publication Date: 2011-11-22
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
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  • 9
    Publication Date: 2003-10-01
    Print ISSN: 0882-8156
    Electronic ISSN: 1520-0434
    Topics: Geography , Physics
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  • 10
    Publication Date: 2018-10-23
    Description: In radar meteorology, greater interest is dedicated to weather radars and precipitation analyses. However, cloud radars provide us with detailed information on cloud particles from which the precipitation consists of. Motivated by research on the cloud particles, a vertical Ka-band cloud radar (35 GHz) was installed at the Milešovka observatory in Central Europe and was operationally measuring since June 2018. This study presents algorithms that we use to retrieve vertical air velocity (Vair) and hydrometeors. The algorithm calculating Vair is based on small-particle tracers, which considers the terminal velocity of small particles negligible and, thereby, Vair corresponds to the velocity of the small particles. The algorithm classifying hydrometeors consists of calculating the terminal velocity of hydrometeors and the vertical temperature profile. It identifies six hydrometeor types (cloud droplets, ice, and four precipitating particles: rain, graupel, snow, and hail) based on the calculated terminal velocity of hydrometeors, temperature, Vair, and Linear Depolarization Ratio. The results of both the Vair and the distribution of hydrometeors were found to be realistic for a thunderstorm associated with significant lightning activity on 1 June 2018.
    Electronic ISSN: 2072-4292
    Topics: Architecture, Civil Engineering, Surveying , Geography
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