- 期刊
第一階段TAMEX密集觀測之個案對流系統與降水研究
Case Study of the MCSs and Rainfall during TAMEX/PHASE I
摘要
本文利用傳統觀測資料，逐時降水量及每三小時間距之衛星資料，分析導致1986年6月4～6日台灣地區豪雨之主要對流系統之演進及可能機制，對流強度之海陸差異與日夜變化，以及對流與降水量之關係。結果顯示，除地面鋒面擾動輻合與鋒面攀升，低對流層西南氣流與高對流層輻散為導致MCSs形成與加強之有利環境條件外，地形效應（攀升、加熱）及日間海風造成之局部輻合與夜間陸風與MCS前緣外流邊界造成之低層輻合均為導致系統形成與加強之主要機制。對流系統之強度變化主要發生在成熟前3小時至後3小時，且減弱速率遠比增強速率為快。對流中心在海上者，其強度在深夜至清晨最強，屬夜強日弱型，而在陸上則自午後至傍晚達最強並持續至午夜，屬日強夜弱型。陸上日間較強顯係因太陽加熱及海風輻合而來，海上夜間最強可能因雲區與非雲區輻射差異導致局部環流日夜變化而來。此外，對流強度在鋒區亦有明顯的日夜變化，對流在南北部之強度亦有不同，並俱有海陸差異。雨量多寡與雲系生命階段有關，較大雨量發生在成長期至成熟期且在成熟期最大，減弱期則迅速減少。短時內一地區雨量之多寡亦與雲系面積及對流強度（雲頂溫度）有關。
並列摘要
Conventional observations, hourly rainfall and three-hourly satellite data were used to study the evolution and the possible mechanisms of Mesoscale Convective Systems (MCSs) which produced heavy rainfall on 4-6 June. 1986. The land-sea difference and diurnal variations of the MCSs as well as the relationship between the precipitation and the evolution of convective systems were analyzed. Results show that the frontal forcing. SW flows t lower troposphere and the divergence at upper-level troposphere were the favorable conditions for the formation and intensification of MCSs. The terrain effects (mechanical lifting and heating), the local convergence produced by the daytime sea-breeze and the low-level convergence induced by the leading edge of outflow boundary of MCS and the night-time land-breeze were the possible triggering mechanisms for the formation and intensification of the MCSs.The intensity variation of convective systems occurred mainly before and after three hours of the mature stage. The weakening rate was far faster than the intensifying rare. Convective systems over the ocean, reached their maximum from the late afternoon to early evening and maintained their intensity until before midnight (day strong/night weak type). Convective systems over land were intensified in daytime probably due to the solar heating and the local convergence produced by sea-breeze. Those over the ocean reached their maximum perhaps due to the diurnal variations of local circulation driven by the radiation difference between the cloud and cloud-free area. The diurnal variations of convective systems in the frontal area were also obvious. The intensity of MCSs over northern part of 24°N was different from those over the southern part. Their intensity also contained land-sea difference. The rainfall amount is positively related to the different lifetime of the MCSs. Heavier rainfall occurred during the intensifying and maturing stages. After mature stage the rainfall amount decreased rapidly. The rainfall amount over a specific area is also closely related to the area and the intensity of MCSs.