梅雨期東亞及西太平洋中尺度對流系統之氣候特徵

Climatological Aspects of the Mesoscale Convective Systems over Subtropical China and the Western North Pacific during Mei-Yu Season of 1981-1983

陳泰然(George Tai-Jen Chen) ； 吳倩雯(Chien-Wen Wu) ； 紀水上(Shui-Shang Chi)

《大氣科學》 13卷1期 (1986/03) Pp. 33-45

摘要

本文利用1981－1983年5－6月梅雨期GMS衛星雲圖資料，分析華南及西太平洋地區中尺度對流系統（MCS）之氣候特徵。將MCS生命史分成初生期、加強期、成熟期、減弱期及消散期等五個階段，分析各階段之頻率日夜變化、海陸差異、地理分佈及移行路徑。結果顯示，梅雨期MCS之延時與美國暖季之MCC者相近。MCS之生命期與其水平尺度成正相關且隨季節演進而增長，顯示其為熱力驅動之天氣系統。MCS在陸上一般向東南移動，出海後則轉向東或東北進行。陸上MCS初生期頻率之午後最高峯，顯係因太陽加熱而來。海上與陸上MCS之加強期及／或成熟期頻率之清晨最大值，可以雲區與非雲區輻射差異解釋，而導致陸上成熟期深夜之高峯頻率機制則有待進一步研究。

並列摘要

GMS satellite pictures for the Mei-Yu season (May-June) of 1981-83 were used to study the climatological characteristics of the mesoscale convective systems (MCS) over subtropical China and the Western North Pacific. Life cycle of the MCS was divided into five stages. They are initial, intensifying, mature, weakening, and dissipating stages. Diurnal variations, land-sea differences, and geographical distribution of MCS frequencies as well as moving tracks were analyzed for each stage.Results show that the duration of Mei-Yu MCS's is nearly the same as that of the U. S. MCC's. The duration of MCS is positively correlated to the horizontal scale of MCS and increases as the season moves on. This tends to suggest that the MCS's are thermally driven weather systems. In general, MCS moves southeastward over land and turns towards east or northeast after it moves into the ocean. The early afternoon frequency peak of the initial-stage MCS's over land can be explained by the solar heating. The morning peak frequency for the intensifying-stage and/or mature-stage MCS's over land and the ocean is perhaps due to the radiational difference between the cloud and cloud-free area. The processes responsible for the mid-night peak frequency of mature-stage MCS over land are not clear and need further studies.