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Broadband radiation scheme fully interacting with clouds
Mašek, Ján ; Brožková, Radmila (advisor) ; Bednář, Jan (referee) ; Kubátová, Brankica (referee)
The parameterization of radiative transfer is a part of numerical weather prediction and general circulation models that is both essential and computationally very expensive, and is therefore subject to neverending compromises between accuracy and computational cost. The present thesis offers an improvement to the existing broadband radiation scheme by revising its critical components - gaseous transmissions, cloud optical properties, and calculation of internal longwave exchanges. The accuracy of the fullspectrum broadband approach is thus raised to the level required for the short range numerical weather forecast. The intermittent update of broadband gaseous transmissions is introduced as a new component, reducing computational cost while preserving the full cloudradiation interaction. The scalability of longwave computations is ensured by adopting the net exchanged rate decomposition with bracketing, improved by an intermittently applied selflearning algorithm determining the interpolation weights. It has been demonstrated that under conditions of operational weather forecasting, this developed scheme is fully competitive with the mainstream approach, due to the improved error balance between the...
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Study of bias correction for data assimilation in NWP model ALADIN
Benáček, Patrik ; Brožková, Radmila (advisor) ; Sokol, Zbyněk (referee)
Satellite sensor AMSU-A provides passive measurements of the radiation emitted from the earth's surface and the atmosphere. The radiances contain temperature and humidity information, but in order for this information to be directly assimilated in a numerical weather prediction (NWP) system, biases between the observed radiances and those simulated from the model first guess must be corrected. After the introduction we recall a notion of analysis, data assimilation and implementation in numerical model ALADIN, which is used by the Czech Hydrometeorological Institute. Then we introduce two radiance-bias correction schemes so-called Harris and Kelly method and variational correction method VarBC. In the last part of my thesis are presented the results of both correction methods for satellite measurements, available in one month periods, and effect of correction demonstrated on the figures.
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Study of AMDAR data in NWP model ALADIN
Bučánek, Antonín ; Brožková, Radmila (advisor) ; Brechler, Josef (referee)
The impact of assimilation (using 3D-Var method) of aircraft measurements on forecasts of the numerical model ALADIN is studied in the present work. Methods of measuring several meteorological parameters by aircrafts and their recording to AMDAR message are shown. So called BLUE equation for production of an analysis (the best assessment of the state of atmosphere represented by a numerical model) is deduced. The equivalence between the BLUE equation and a minimization of the quadratic functional used by 3D-Var is shown. Essentials steps of integrating meteorological measurements to assimilation procedure are outlined. The process of assimilation used in Czech Hydrometeorological Institute is shown and the results of aircraft measurements assimilation are presented.
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