利用中壢特高頻雷達觀測潭美颱風的降雨現象

Observation of TRAMI typhoon precipitations made with Chung-Li VHF radar andground-based disdrometer

陳睿祥(Ruei-siang Chen)

指導教授 ： 朱延祥教授

國立中央大學/地球科學學院/太空科學研究所/碩士(2014年)

摘要

本次研究是利用中壢52MHz特高頻雷達以及地面二維雨滴譜儀(Disdrometer)來研究紀錄潭美颱風的降水情形，可分別得到空中降水粒子之終端速度、回波功率、頻譜寬、大氣回波功率、大氣垂直速度、頻譜寬以及地面之降雨率、雨滴粒徑分佈等等。
本次觀測資料為潭美颱風降水事件為2013年8月20日15:01~23:34LT以及8月21日與8月22日這兩天的降水資料，首先區分是冷降水還是暖降水的降水事件，冷降水是固體冰晶往下掉經亮帶後降落到0^° C等溫線以下變液態雨，而暖降水是強上升氣流從底部帶降水粒子衝到2~4km或以上的高度所產生的降雨現象，再利用空中降水粒子的終端速度和回波功率之間的關係，可推得空中降水粒子指數型態及伽瑪型態兩種雨滴粒徑分佈的參數N_0，再與地面雨滴譜儀得到的N_0作散佈圖，只取冷降水事件且是指數型態雨滴粒徑分佈的情況下，斜率較接近於1且相關係數非常好。
在8月20日約19:42在8-10km附近發現有強上升氣流的出現，平均都卜勒速度最大將近15m/s，所以我們取8月20日19:02:44~20:03:10這段時間來作大氣回波功率與頻譜寬、大氣回波功率與垂直速度之間的散佈圖。發現高層(7.05km~12.3km)的相關係數良好比率都優於低層(1.65km~6.9km)。
比較融解層(5.4km)以上的冰晶和過冷水的特性，以終端速度絕對值2.5m/s當作冰晶與過冷水的篩選條件大致區分兩者，各個高度平均回波功率的比較上兩者差異在8-11dB，平均頻譜寬的比較上兩者差異在0.15Hz以上。

關鍵字

中壢特高頻雷達 ； 降水 ； 颱風

並列摘要

The research is to record the rainfall phenomenon of TRAMI-typhoon.We can obtain precipitation terminal velocity, echo power, rain fall rate, DSD and the spectral width etc by using the Chung-Li 52MHz VHF radar and ground 2DVD- Disdrometer.
The data is the events from August 20th 15:01~August 22th,2013.We can distinguish the cold precipitation events and the warm precipitation events with the air vertical velocity and bright band,and make scatter diagram by using the relation between precipitation terminal velocity and echo power in air to obtain the N_0 from exponential and gamma of DSD of precipitation particle and the N_0 from ground 2DVD- Disdrometer. The slope is closer to 1 and the correlation coefficient is very well,when only takes not only the cold precipitation events but the DSD is exponential.
We take the time from August 20th 19:02:04 to 20:03:10 to make the scatter diagram of air echo power with the spectral width,and air echo power with the air vertical velocity,because we found the presence of the strong updraft, average Doppler velocity maximum nearly 15m/s on August 20 at about 19:42 near 8-10 km.Then we found the correlation coefficient ratio of the range 7.05km~12.3km is better than the range 1.65km~6.9km.
We can use the filter criteria to distinguish the character between ice and supercooled above melting layer(5.4km) by terminal velocity greater than 2.5m/s.The average echo power between ice and supercooled water is 8-11dB,and supercooled water is greater than ice about 0.15Hz in average spectral width.We have lightning echo signals in this observing data.

並列關鍵字

Chung-Li VHF radar ； precipitation ； typhoon

參考文獻

characteristic of precipitation at vertical incidence, Rev.

Geophys ., 11, 1-35, 1973.

Batten,L.J., Radar observations of the atmosphere, pp324, University

of Chicago Press, Chicago, Ⅲ, 1973.

Chu,Y.H., and C.H.Lin, The severe depletion of turbulent echo power