ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
4DVAR Numerical Simulation Analysis Using ATOVS Data and Asymmetrical Bogus Data on Landing Typhoon Weipha
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Abstract:
An axisymmetric Bogus vortex at sea level was used in the traditional bogus data assimilation (BDA) scheme. This vortex could not accurately describe the specific characteristics of the typhoon. The reasonable elements of the background field were discarded. And, the assimilation of thermal and humidity elements, and the impact of the largescale environment, were not taken into account. Thus, an asymmetrical typhoon bogus method with blend information from the analysis and the observation is brought forward while the impact of the subtropical anticyclone is considered as well. Then the fast radiative transfer model RTTOV8 is planted into the adjoint model of the fifth generation NCAR/Penn State Mesoscale Model (MM5) to assimilate the brightness temperature and Bogus data based on the fourdimensional variational data assimilation (4DVAR) technique. A group of BDA experiments on landing typhoon “Weipha” for 48hour simulation are studied. The Bogus sea level wind and pressure, and the multisatellite and multiorbital ATOVS data are assimilated. The Noah land surface model is employed in simulation. The results show that, the BDA scheme which assimilates Bogus data alone transmits the Bogus information from the sea surface to high layers, and an asymmetrical threedimensional circulation assorted with the model is brought out, the temperature is indirectly adjusted in whole layers, and a warmcore structure is strengthened. Whereas, the adjusting of humidity is deficient, the environmental fields outside the typhoon area cannot be adjusted well, and the improvement of track forecast is not obvious while the intensity forecast is greatly improved; The employment of Noah land surface model can improve the track forecast after landing; When ATOVS data are assimilated, significant adjustments are made on the humidity condition and environmental fields, lots of mesoscale information is reconfigured, more precise typhoon circulation and more precise thermal and humidity structure in the initial field is obtained. And the advantage of BDA scheme in track and intensity forecast is maintained, the precipitation intensity in forecast is increasing, and the precipitation location is changed.
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