台风麦莎与赤道穿透对流云团的初步比较分析

A preliminary analysis and comparison between Typhoon Matsa (2005) and an equatorial cluster of penetrative convection

  • 摘要: 利用TRMM卫星的测雨雷达、微波成像仪、可见光和红外扫描仪资料详细分析比较了麦莎台风和位于南海南部的赤道穿透对流云团(EPCC)的云高以及降水结构特征。首先,对热带地区对流层到平流层的过渡带(TTL)以及进入TTL的穿透对流云团进行了阐述和定义。然后,分析对比了赤道穿透对流云团和台风麦莎不同生命史阶段的云高、降水结构特征,分析对比结果表明: (1) 在强降水区: 麦莎台风和EPCC的云顶上部均出现了冰粒子散射现象,但EPCC的散射强度强,微波亮温值均低于180 K,并且其雷达云高和红外云顶亮温云高相差较大、云顶亮温曲线平缓。(2) EPCC的深对流数量百分比、穿透对流数量百分比、尤其是穿透对流数量占深对流数量比,都比麦莎台风各阶段的高;在麦莎台风和EPCC(10—20 km)云体中大部分云高集中在10—12 km,但EPCC (10—20 km) 的云高谱相对具有连续性、相对较宽。(3) 麦莎台风以层云降水为主,对总降水量的贡献中也是层云降水贡献大,但是EPCC中却是对流性降水的贡献大,且EPCC对流降水与层云降水的像素数量比值和降水量比值也比麦莎台风的3个时次都高。 (4) EPCC的降水廓线深度无论是层云降水还是对流降水都比麦莎台风深,层云廓线深度达11 km,对流廓线深度达18 km。另外,从EPCC的穿透对流数量百分比比麦莎台风多,层云、对流降水廓线比麦莎台风深这几方面,一定程度上说明了EPCC的局部垂直对流强度比麦莎台风强。

     

    Abstract: Cloud tops and rainfall structures of Typhoon Matsa (2005) and the Equatorial penetration convective cluster (EPCC) which is located in the southern South China Sea are analyzed and compared based on the data from the TRMM Precipitation Radar (PR), TRMM Microwave Imager (TMI) and Visible Infrared Scanner (VIRS). Firstly, the tropical tropopause layer (TTL) and the EPCC which penetrated into the TTL are illuminated and defined. And then, the cloud tops and precipitation structures of Typhoon Matsa and the EPCC are analyzed and compared. The results are as followings: (1) In heavy rain areas, ice particle scattering occurrs at the cloudtop of Matsa and the EPCC, but the scattering intensity of the EPCC is much stronger with 85 GHz brightness temperature all below 180 K and the difference between the cloud tops from the PR and the VIRS for the EPCC being larger as well as the curve of VIRS cloudtop brightness temperature being flat. (2) The percent of samples of deep convection, and the percent of penetration convection, and esp. the percent of deep convection accounted for by penetration convection in the EPCC are more than those in Matsa, with the clouds in the Matsa and the EPCC from 10 to 20 km whose top heights dominate between 10 and 12 km, but the distribution of PR cloud tops between 10 and 20 km in the EPCC relatively continuous and wide. (3) Stratiformis precipitation is the predominant type in Matsa and contributes more rainfall to the total. However, convective precipitation is mainly found in the EPCC with larger ratios of convective area to stratiformis area, convective rainfall to stratiformis rainfall for the EPCC than those for Matsa. (4) The results also show that the profiles of both the convective and stratiformis precipitation for the EPCC are deeper than Matsa with the convective and stratiformis profile depth being 18 and 11 km, respectively. In addition, the fact that, the percent of samples of penetrative convection in the EPCC more than Matsa as well as the profile of convective and stratiformis precipitation deeper than Matsa seems to suggest that the local vertical convective intensity of the EPCC is stronger than Matsa.

     

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