臺灣梅雨季伴隨中尺度低壓之豪雨與雷達回波研究

Study of Rainfalls and Radar Echoes in the Heavy Rainfall Events Accompanied by Mesolow in Mei-Yu Season

陳泰然(George Tai-Jen Chen)

《大氣科學》 18卷3期 (1990/09) Pp. 213-228

摘要

本文選取1983-1987年台灣梅雨季18個伴隨中央山脈以西中尺度低壓之豪雨個案，利用地面逐時降水資料、每6小時地面天氣圖、每12小時850-500 hPa天氣圖與高雄逐時雷達回波資料，以探討中尺度低壓出現前後之降水強度、回波強度與回波面積改變及低壓出現時之綜觀形勢。結果顯示，在中尺度低壓區以南發生之豪雨，低壓出現後雨量與回波強度大增，此可能主要因氣壓梯度與風速之增強導致局部輻合之增強而來，而850 hPa低層噴流入區上升運動亦可能有些貢獻。已存之中尺度對流系統潛熱釋放，可能為中南部中尺度低壓形成之重要因子，而低壓形成後降雨與回波強度再被增強。

關鍵字

梅雨季 ； 中尺度低壓 ； 豪雨 ； 低層噴流

並列摘要

Eighteen cases of heavy rainfall events, which were accompanied by the mesolow to the west of the Central Mountain Range, observed in 1983-1987 Taiwan Mei-Yu season were selected in this study. The surface hourly rainfall, 6 hourly surface charts, 12 hourly upper-level charts (850, 700, 500 hPa) and hourly radar echoes observed at Kaohsiung station were used in the analysis. The spatial and temporal variations of rainfall and radar echoes were analyzed and discussed with respect to the appearance/formations of mesolow. The synoptic situations were also presented at the time of mesolow appearance.Results showed that the rainfall rate and radar echo increased substantially when and after the mesolow appeared. The intensity increase perhaps was due to the increase of local convergence which was caused by the increase of pressure gradient and low-level winds to the south of the mesolow. The upward motion associated with the 850 hPa low-level jet over the anticyclonic side of the entrance region also contributed partially to the occurrence of heavy rainfall. Furthermore, the latent heating associated with pre-existing mesoscale convective system might have served as an essential factor for the formation of mesolow over the central and southern Taiwan. The rainfall and radar echo in turn were enhanced by the appearance of mesolow over the same area.

並列關鍵字

Mei-Yu season ； mesolow ； heavy rainfall ； low-level jet