| Description |
This study attempts to characterize the particular convection type, namely storm morphologies, convective properties, and microphysics, of different weather regimes within the East Asian Summer Monsoon (EASM). Defined rain bands and associated rainfall characteristics are examined in terms of population, location, variability, and rainfall frequency. Though the Mei-Yu rain bands produce a relatively large rain belt over South China and Taiwan during mid-May to mid-June, and over the Yangtze River region during mid-June to mid-July, rainfall maxima and heavy precipitation are most frequent over specific locations. Generally, the frequency of storms with high echo tops, significant convection, and evident ice scattering signature is greatest in post-Meiyu and break periods, less so during the active Mei-Yu, and least frequent before the monsoon onset. However, preseason, as well as break periods, has a larger fraction of intense convection that behaves more like the classic continental tropical convection with major ice-based rainfall processes. Specifically, preseason and break periods have a larger fraction of rainfall contributed from storms with a 40-dBZ convective core extending above 7-8 km. By comparison, active Mei-Yu convection more closely resembles classic tropical maritime convection with relatively more importance of "warm-rain" collision and coalescence processes with weaker convection but heavy precipitation. Monsoon precipitation over the Yangtze River region, though having similar size and cloud top, differs from its counterpart in South China on convective properties, vertical structures, and rainfall contribution by storm types. Based on Tropical Rainfall Measuring Mission (TRMM) climatology, the EASM is comparable to other monsoon regimes by having convective properties intermediate between the intense convective systems over continents, and the weaker convective systems found in the classic maritime precipitation regimes. Analysis based on Terrain-influenced Monsoon Rainfall Experiment (TiMREX) observations indicates that most of the heavy rainfall is associated with Mei-Yu rain bands, strongly influenced by upstream low-level jets, unstable upstream conditions, but a more nearly moist neutral storm environment. A particular long-duration heavy precipitation event is analyzed in detail, and features continuous development of "back-building" new convection under the influence of an extensive precipitation-created cold pool and substantial orography downstream. |
