利用雨滴譜儀分析不同降水系統之微物理特性研究

Use distrometer analyze different precipitation type

吳舜華(Shun-Hua Wu)

指導教授 ： 林沛練

國立中央大學/地球科學學院/大氣物理研究所/碩士(2006年)

摘要

觀測雨滴粒徑分布(Drop size distribution：DSD)可應用於氣象、水文領域。而且平均的雨滴粒徑分布可代表某個地區的降雨型態，將此雨滴粒徑分布應用於雲模式中，可以了解雲的成長以及垂直剖面上雨滴的形成與潛熱釋放的情形。由此可知雨滴粒徑分布對於降雨特性的了解扮演很重要的角色，本研究即使用雨滴譜儀觀測的資料進行雨滴粒徑分布的特性分析。

本研究首先比較光學式和撞擊式雨滴譜儀觀測雨滴粒徑分布分降雨率之差異性。在雨滴粒徑分布方面，兩種雨滴譜儀在雨滴粒徑為1.5〜2.5mm的雨滴個數量測有很好的一致性。撞擊式雨滴譜儀在弱降雨率時，會低估最小雨滴個數，因儀器之限制；而劇烈降雨時，則會低估小雨滴和大雨滴的個數，此結果與Tokay(2001)的研究結果一致。此外由雨滴粒徑分布參數與降雨積分參數也可看到此兩種雨滴譜儀之觀測結果很相似。

進一步應用光學式雨滴譜儀所觀測到長期且大量的雨滴譜資料進行不同季節與不同降雨型態之降雨特性分析。各個季節中值體積直徑(D0：Median Volume Diameter)隨降雨率都有明顯之變化，D0值由小到大之分布為：冬季，春季，颱風季，秋季，梅雨季。

在不同降雨型態中，降雨率大於20mm/hr時，鋒面與颱風降雨型態的D0值較局部降雨型態明顯小，可知在強降雨率且受鋒面或颱風天氣系統影響下，雨滴易破碎，不易成長。相較之下，局部降雨型態則較易出現大雨滴的粒徑。

在相同降雨型態之季節性差異分析發現：(1)局部降雨型態：冬季與春季之局部降雨DSD特性較為相似；梅雨季與颱風季之局部降雨DSD特性也比較相似；而秋季之局部降雨特性則介於冬季與梅雨季之間。(2)鋒面降雨型態深受季節之影響，D0值分布：冬季、春季較大，梅雨季次之，秋季最小。 (3)颱風降雨型態與季節交替沒有顯著關連。

關鍵字

雨滴譜儀

並列摘要

Measurements of the drop size distribution(DSD) have a broad range of applications in meteorology and hydrology.
The characteristics of an averaged DSD,which represents a precipitation type in a climatological region,are important for cloud-modeling studies.
The observations were designed to test how accurately they measure drop size distribution by Impact(JWD) and Optical(2DVD) disdrometers.The comparison of DSDs,raindrop in 1.5〜2.5mm showed good agreement between two types of disdrometers.
The Joss-Waldvogel disdrometer underestimate small drop size in weak rainfall rate, and underestimate small and big drop size in strong rainfall rate.Beside,the Gamma parameter distribution also showed good agreement between two types of disdrometers.
Further more, apply A long-period and copious data observed by Optical disdrometer(2DVD) to analyze the precipitation characteristics during different season and different precipitation type. In different season analysis, D0 value in each season varies with rainrate, and the distribution of D0 value from large to small is winter，spring，typhoon， fall ，meiyu season.
In analysis of different precipitation type, the D0 value of the fronal type and typhoonic type is apparent small than the local precipipation type when R>20mm/hr.It might result from the drop broken easily and evolved hardly when it is in strong rainrate affected by the frontal system or typhoon. Local precipipation type usually have big drop size distribution.
In the same precipipation type analysis of different season，we found：(1)The local precipipation type: the DSD in winter is similar with spring. The DSD in meiyu season is similar with typhoon season. The DSD in fall is between winter and meiyu season. (2)The DSD of front precipipation type is seasonal dependent. The distribution of D0 value from large to small is : winter〜spring>meiyu>fall(3)The DSD of typhoon precipipation seems seasonal independent.

並列關鍵字

distrometer

參考文獻

林位總,2004：利用二維雨滴譜儀研究雨滴譜特性, 國立中央大學碩士論文,89頁

Atlas, D., and C. W. Ulbrich. 1977：Path- and Area-Integrated Rainfall Measurement by Microwave Attenuation in the 1-3cm Band. J. Appl. Meteor., 16, 1322-1331.

Chen C. S., and Y. L. Chen, 2003：The Rainfall Characteristics of Taiwan. Mon. Wea. Rev., 131,1323-1341.

Double-moment Multiple-phase Four-Class Bulk Ice Scheme.

PartⅡ：Simulations of convective Storms in Different Large-