19B.8 Sensitivities of Very Short-Term Numerical Prediction to Polarimetric Radar Data Assimilation: Typhoon Soudelor (2015)

Wednesday, 30 August 2017: 12:15 PM
St. Gallen 1&2 (Swissotel Chicago)
Chih-Chien Tsai, Taiwan Typhoon and Flood Research Institute, Taipei, Taiwan; and Y. Jung

A radar forward operator for reflectivity (ZH), differential reflectivity (ZDR) and specific differential phase (KDP) that follows the CAPS Polarimetric Radar Data Simulator has been incorporated into a regional data assimilation system employing the local ensemble transform Kalman filter. Utilizing this system and the polarimetric radar data from Central Weather Bureau’s RCWF WSR-88D radar, several assimilation experiments as well as a control experiment with no data assimilation (NoDA) have been carried out for a heavy rainfall event in Taiwan associated with Typhoon Soudelor (2015). The sensitivities of the analyses and very short-term forecasts to different assimilated observation variables have been investigated. For the final-cycle analyses, assimilating ZH or KDP greatly corrects the over-forecasts of ZH and KDP in NoDA but not that of ZDR; on the other hand, assimilating ZDR corrects the over-forecast of ZDR in NoDA to a certain extent but over-corrects those of ZH and KDP. For the 1-hour rainfall forecasts, assimilating any of ZH, ZDR and KDP results in similar and significant improvements compared with NoDA. Further analyses and more experiments with various cloud microphysical schemes and assimilation strategies are in progress.
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