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  • Data Assimilation
Type of Medium
Language
Year
  • 1
    Language: English
    In: Tellus A: Dynamic Meteorology and Oceanography, 01 January 2011, Vol.63(2), pp.263-282
    Description: A forward operator for Global Positioning System (GPS) slant total delay (STD) data and its adjoint were implemented into the Mesoscale Model version 5 (MM5) 4DVAR system to investigate its impact on quantitative precipitation forecasting (QPF)....
    Keywords: Meteorology & Climatology
    E-ISSN: 1600-0870
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  • 2
    Language: English
    In: Meteorologische Zeitschrift, 01 December 2008, Vol.17(6), pp.867-885
    Description: This article describes the development of tools for routine 4-dimensional variational data assimilation of Global Positioning System Slant Total Delay (STD) data in the framework of the MM5 system at the Institute of Physics and Meteorology of the University of Hohenheim. The Slant Total Delay forward operator is introduced which allows model validation and the assimilation in the Message-Passing Interface environment. An experiment is conducted which highlights the importance of accurate model physics in the variational assimilation system. We demonstrate that the model minus observation statistics of STD data crucially depends on the convection scheme and the implementation of horizontal diffusion. A set of modifications to the existing non linear, tangent linear and adjoint model is presented. These include an improvement of the horizontal diffusion scheme and the implementation of the Grell cumulus convective scheme in order to eliminate the observed systematic tendency in the model minus observation statistics of the STD data and precipitation in mountainous terrain. A first assimilation experiment with the improved MM5 variational assimilation system shows promising results.
    Keywords: Meteorology & Climatology
    ISSN: 0941-2948
    E-ISSN: 1610-1227
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  • 3
    Language: English
    In: Quarterly Journal of the Royal Meteorological Society, 137(S1):3-30, 24 February 2011, Vol.137(S1)
    Description: Within the frame of the international field campaign COPS (Convective and Orographically-induced Precipitation Study), a large suite of state-of-the-art meteorological instrumentation was operated, partially combined for the first time. The COPS field phase was performed from 01 June - 31 August 2007 in a low-mountain area in southwestern Germany/eastern France covering the Vosges Mountains, the Rhine valley and the Black Forest Mountains. The collected data set covers the entire evolution of convective precipitation events in complex terrain from their initiation, to their development and mature phase up to their decay. 18 Intensive Operation Periods (IOPs) with 34 operation days and 8 additional Special Observation Periods (SOPs) were performed providing a comprehensive data set covering different forcing conditions. In this paper an overview of the COPS scientific strategy, the field phase, and its first accomplishments is given. Some highlights of the campaign are illustrated with several measurement examples. It is demonstrated that COPS provided new insight in key processes leading to convection initiation and to the modification of precipitation by orography, in the improvement of QPF by the assimilation of new observations, and in the performance of ensembles of convection permitting models in complex terrain.
    Keywords: Environmental Sciences ; Complex Terrain ; Convection ; Performance ; Atmospheric Precipitations ; Field Tests ; Climate Models ; Meteorology & Climatology ; Environmental Sciences
    ISSN: 0035-9009
    E-ISSN: 1477-870X
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  • 4
    Language: English
    In: Journal of Atmospheric and Oceanic Technology, 08/2008, Vol.25(8), pp.1437-1453
    Description: The impact of water vapor observations on mesoscale initial fields provided by a triangle of Raman lidar systems covering an area of about 200 km x 200 km is investigated. A test case during the Lindenberg Campaign for Assessment of Humidity and Cloud Profiling Systems and its Impact on High-Resolution Modeling (LAUNCH-2005) was chosen. Evaluation of initial water vapor fields derived from ECMWF analysis revealed that in the model the highly variable vertical structure of water vapor profiles was not recovered and vertical gradients were smoothed out. Using a 3-h data assimilation window and a resolution of 10-30 min, continuous water vapor data from these observations were assimilated in the fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5) by means of a four-dimensional variational data analysis (4DVAR). A strong correction of the vertical structure and the absolute values of the initial water vapor field of the order of 1 g kg-1 was found. This occurred mainly upstream of the lidar systems within an area, which was comparable with the domain covered by the lidar systems. The correction of the water vapor field was validated using independent global positioning system (GPS) sensors. Much better agreement to GPS zenith wet delay was achieved with the initial water vapor field after 4DVAR. The impact region was transported with the mean wind and was still visible after 4 h of free forecast time.
    Keywords: Scientific Research ; Clouds ; Mean Winds ; Water Vapor in the Atmosphere ; Lidar Applications ; European Centre for Medium-Range Weather Forecasts ; Humidity ; Mesoscale Model Mm5 ; Global Positioning System (Gps) Satellite ; Data Analysis ; Data Assimilation ; Water Vapor Profiles ; Evaluation ; Water Vapor ; Assessments ; Profiles ; Structure ; Humidity ; Model Testing ; Wind ; Model Studies ; Germany, Brandenberg, Lindenberg ; Forecasting (551.509.1/.5) ; General ; General;
    ISSN: 0739-0572
    E-ISSN: 1520-0426
    Source: CrossRef
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  • 5
    Language: English
    In: Monthly Weather Review, 01/2006, Vol.134(1), pp.209-230
    Description: Four-dimensional variational assimilation of water vapor differential absorption lidar (DIAL) data has been applied for investigating their impact on the initial water field for mesoscale weather forecasting. A case that was observed during the International H2O Project (IHOP_2002) has been selected. During 24 May 2002, data from the NASA Lidar Atmospheric Sensing Experiment were available upstream of a convective system that formed later along the dryline and a cold front. Tools were developed for routinely assimilating water vapor DIAL data into the fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5). The results demonstrate a large impact on the initial water vapor field. This is due to the high resolution and accuracy of DIAL data making the observation of the high spatial variability of humidity in the region of the dryline and of the cold front possible. The water vapor field is mainly adjusted by a modification of the atmospheric wind field changing the moisture transport. A positive impact of the improved initial fields on the spatial/temporal prediction of convective initiation is visible. The results demonstrate the high value of accurate, vertically resolved mesoscale water vapor observations and advanced data assimilation systems for short-range weather forecasting.
    Keywords: Scientific Research ; Drylines ; Cold Fronts ; Water Vapor Distribution ; Moisture Transport ; Lidar ; Humidity ; Mesoscale Model Mm5 ; Convective Systems ; Wind Fields ; Weather Forecasting ; Data Assimilation ; Spatial Variability ; Forecasting (551.509.1/.5) ; General ; Methods of Observation/Computations (551.501);
    ISSN: 0027-0644
    E-ISSN: 1520-0493
    Source: CrossRef
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