利用10年NCEP/NCAR逐日再分析资料和GPCP-1DD降水资料,依据频次分析,研究了季节尺度副热带高压(副高)中心内降水分布的特点。研究结果表明:副高中心内四季均存在降水,其中夏季副高中心降水频次为40%-80%,而其他季节副高中心降水频次不超过50%;季平均副高中心降水率冬季约1-2mm/d、夏季不超过4mm/d,它对局地总降水的贡献变化在30%-90%,其中,夏季的贡献基本为50%-90%,其他季节的多数区域贡献一般不超过40%。统计表明,夏季副高中心上升运动频次变化范围为25%-75%,其他季节上升运动频次在25%以下。研究结果还发现夏季西太平洋副高中心频次约30%出现在中国东部大陆,相应的降水频次及上升运动频次分别为25%和15%,从而形成夏季中国东部一种独特的降水天气形势,即500hPa副高控制下的降水。另外,文中还指出副高中心内降水有一半以上出现在500hPa存在上升运动的情况下,而半数以下的降水出现时,500hPa存在下沉运动,前者降水可能为深厚性质,而后者则可能表明为浅薄降水。
Based on the NCEP/NCAR reanalysis daily data and GPCP-1DD precipitation data from 1997 to 2006, seasonal characteristics of precipitation occurring in the core area of the subtropical high was investigated by a frequency analysis method. The results indicate that precipitation phenomena occurs in the core area of the subtropical high in each seasons. In summer there exists from 40 % to 80 % precipitation frequency in the area against less than 50 % frequency in other seasons. Generally, the seasonal mean rain rate inside the core area is about 1 2 mm/d in winter and less than 4 mm/d in summer, which contributes about 30 % - 90 % precipitation amount to the local total precipitation. While in summer such contribution is about 50 % - 90 % basically contrary to less than 40 % in other seasons. Statistically, the occurrence frequency of updrafts within the core area of the subtropical high varies from 25 % to 75% in summer and less than 25% in other seasons. Furthermore, results also expose that there is about 30% frequency for the core area of the subtropical high existing over the eastern parts of China in summer, which is corresponding to 25 % and 15 % frequency for precipitation and updrafts, respectively. That is the so called a unique precipitation weather pattern, i.e. precipitation under the controlling of the core of the subtropical high, in summer over the eastern parts of China. Additionally, it is found that more than half of the precipitation occurring in the core area of the subtropical high is accompanied with updrafts at 500 hPa against to the rest accompanying with downdrafts. The former may represent deep precipitation circumstances whereas the latter may hint shallow precipitation situations in the core area of the subtropical high.