冬、夏季热带及副热带穿透性对流气候特征分析

文中利用热带测雨卫星 (TRMM) 搭载的测雨雷达 (PR) 1998~2007年的探测结果, 就热带及副热带地区穿透性对流的频次、条件降水强度及垂直廓线等特征进行了分析。研究结果表明: 深对流和穿透性对流都主要发生在热带辐合带 ( ITCZ)、南太平洋辐合带 (SPCZ)、亚洲季风区、20°N以南的非洲以及美洲等地区, 它们的空间分布具有明显的地域性和季节变化特征, 而且陆地深对流更容易发展成为穿透性对流, 但绝大部分地区的穿透性对流频次不超过0.2%。对穿透性对流条件降水强度的分析表明, 热带及副热带大部分地区的穿透性对流条件降水强度在10 mm/h以上, 且洋面的条件降水强度要比陆地大, 但由于其频次较小导致其对总降水的贡献并不大。尽管深对流和穿透性对流降水廓线的外形比较相似, 但相同的高度, 深对流的降水强度要比穿透性对流偏小, 而且这种差异随海陆和纬度的不同而有所区别。此外, 热带地区 (15°S~15°N) 冬、夏季深对流和穿透性对流降水廓线都只存在较小差异, 并没有显示出明显的季节变化。

Climatological Characteristics of Overshooting Convective Precipitation in Summer and Winter over the Tropical and Subtropical Regions

The climatological characteristics of overshooting convective precipitation including frequency, conditional rain rate, and precipitation profiles are investigated based on the measurements of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) during 1998-2007 over the tropical and subtropical areas. Results indicate that both deep and overshooting convections are mainly distributed over the intertropical convergence zone, the South Pacific convergence zone, the Asia monsoon region, Africa south of 20°N, and America. The distributions of deep and overshooting convections show remarkable regionality and seasonal variations. Meanwhile, deep convections over land penetrate into TTL (Tropical Tropopause Layer) more easily than those over ocean. And totally, the overshooting convection frequencies are under 0.2% over most of the tropical and subtropical areas. Conditional rain rates of the overshooting convections over most regions exceed 10mm/h, and those over ocean are higher than that over land. But the contribution of the overshooting convections to total rain is small due to the low frequency. The shapes of deep and overshooting convective precipitation profiles are similar, but rain rates of overshooting convections are larger than that of deep convections, and the differences also show remarkable regionality. Moreover, seasonal variations of deep and overshooting convective precipitation profiles over the tropical areas (15°S-15°N) are minimal.