Monsoon Rainfall Characteristics: Precipitation Types and Associated Environment Regimes observed during SoWMEX/TiMREX

In this study, the composited hybrid scan radar reflectivity data of the Central Weather Bureau (CWB)'s Quantitative Precipitation Estimation Segregation Using Multiple Sensors (QPESUMS) system and the lightning data of the Taiwan Power Company (Taipower)'s Total Lightning Detection System (TLDS) are used to characterize the significant continuous rainfall periods in southwestern Taiwan during the 2008 Mei-Yu season. High temporal resolution sounding data taken during SoWMEX/TiMREX are used to describe the environment conditions.

A total of 40 rainfall events are identified in the 2008 Mei-Yu season. The results indicate that, based on the initiation location, the precipitation events can be classified into three types: land, oceanic, and mixed. The former two types are evenly distributed (18:17) and occupy most of the cases. For the time of development, the land events usually begin in the daytime with shorter durations. In contrast, the oceanic events have their initiations in the nighttime and persist longer. Most of the land events are related to the afternoon thunderstorms and reveal pronounced diurnal cycle signal. In terms of spatial distribution, on the average, the land-type (oceanic-type) precipitating systems are more concentrated (widespread) with higher fraction of convective (stratiform) precipitation and higher (lower) lightning density.

For the environmental conditions, the land (oceanic) events are associated with larger (smaller) convective available potential energy (CAPE) and smaller (larger) convective inhibition (CIN). Otherwise, the composited soundings show that the oceanic-type has a much stronger and moister southwesterly flow over the lower troposphere than the land-type.

Using dropsondes and shipsondes, it is found the upstream southwesterly possesses quite different characteristics from the one over the plain area in the southwestern Taiwan. The influence of terrain is indicated.

*corresponding author: Jouben@ntu.edu.tw