Application of Doppler Radar Data Assimilation on the Retrieval of a Mei-yu Front within the Taiwan Strait Associated with a Heavy Rain Event

With the incorporation of Doppler radar radial velocity by MM5/3DVAR system, a Mei-yu frontal system related to a coming heavy rain episode over southwestern Taiwan was retrieved within the Taiwan Strait on 6 June 2003. Significant frontal wind-shift (the prefrontal southwesterlies/the postfrontal northeasterlies) was reproduced over ocean, which was not captured by the NCEP reanalysis and the other datasets. Especially, the convectively induced strong wind (>20 ms-1) and mesoscale kinematic properties (horizontal convergence and cyclonic vorticity) were retrieved along the surface frontal zone. Also, the orographically induced windward anticyclonic vorticity (ridge) and leeside cyclonic vorticuty (trough) were reproduced over the southern Taiwan.

For the prediction of the heavy rainfall over southwestern Taiwan on 7 June 2003, the simulated rainfall distribution using Doppler radar data assimilation revealed a better performance.