dc.description.abstract | In this study, a typical case for heavy rainfall associated Mei-Yu front on 14-15 June 2008, also categorized as the IOP-8 event during the SoWMEX. We analyzed the observation data and compared with the WRF model simulations. One single moment microphysics scheme (WSM6) and three double moment microphysics schemes (WDM6, Morrison, Thompson) are chosen to perform sensitivity tests, in order to evaluate different schemes ability to simulate the Mei-Yu frontal rainfall near Taiwan area.
This rainfall case produced heavy precipitation over southern and southwestern Taiwan, that associated with the interactions of the Mei-Yu front and the orographic
over southern Taiwan. The WRF-simulated synoptic field, wind pattern and geopotential height were consistent but the subtropical high weaker than observation. Radar echoes show the precipitation system encountered southern Taiwan, and all the experiments simulated two rain bands were similar with S-pol (S band dual-polarization Doppler radar) radar observation but delayed 2 hours.
Reflectivity CFAD (Contoured frequency with altitude diagrams) of four microphysics simulations compared with CFAD of S-pol radar echoes were all overestimated. WDM6 simulated bright bands were more obvious than other
schemes. Vertical velocity CFAD show that four schemes simulated updraft was similar to observation, but downdraft underestimated in all simulations.
We compared with the PID (Particle Identification) vertical percentage distribution of observational analysis and simulations, the Thompson simulated produced unreasonable amount of snow because of power-law droplet size distribution; WSM6 scheme produced more amount of rainwater at high levels which without forecasting rainwater number concentration. Morrison and WDM6
scheme is not biased toward a specific type of hydrometer.
We analzed the JWD (Joss-Waldvogel disdrometer) data and compared with the model simulated rainwater number concentration time series. WDM6 schemes simulated time series show the most similar evolution to observation analysis.
Finally, WDM6 simulation was the most reasonable, but still need to consider the model error, and the error of the observations. | en_US |