利用TRMM卫星分析西北太平洋各等级热带气旋降水分布特征

ANALYSIS OF TROPICAL CYCLONE PRECIPITATION FOR DIFFERENT CLASS OF INTENSITY IN NORTHWEST PACIFIC WITH TRMM DATA

为了更好掌握西北太平洋热带气旋(Tropical Cyclone,TC)降水的分布特征,将2003—2009年TRMM资料同TC最佳路径数据集相匹配,共得到这7年中118个TC的336时次个例,包括强热带风暴、台风、强台风和超强台风4种强度等级样本,建立了TRMM卫星监测西北太平洋TC的样本数据库。在此基础上,选取距TC中心300 km范围为研究区域,每间隔10 km为圆环计算其降雨方位平均值,对各等级TC平均地表降雨率的径向分布、不同降雨率和降水类型的平均出现频率和降水贡献比例以及沿TC移动方向上各象限平均降雨率分布等特征进行统计分析,研究结果表明:(1)随着强度等级的增加,TC平均地表降雨率逐渐增加,并在径向方向上表现出单峰型分布特征,降水出现频率和贡献比例的峰值也逐渐向8 mm/h附近的峰值靠拢;(2)层性降水在研究区域内占统治地位,而对流性降水主要集中在眼壁附近;(3)各象限平均降雨率相差不大,相对而言,沿TC移动的前侧降雨率更大,而右后侧最小。

Combined with TRMM products and Tropical Cyclone （TC） best track data in the Northwest Pacific from 1 January 2003 to 31 December 2009, a total of 118 TCs, including 336 TC precipitation observations for the same period of time, are established as a TRMM TC database to understand the characteristics of TC precipitation distribution better. The database is grouped into four intensity classes： Severe Tropical Storm（STS）, Typhoon（TY）, Severe Typhoon（STY） and Super Typhoon（SuperTY）. For each of the TC classes, mean rainfall distribution is computed for the area from the TC center within 300 km radius at the intervals of l0 km annuli, the axisymmetric component of TCs rainfall is represented by the radial distribution of the azimuthal mean rain rate, and mean rain rates, rain types occurrence and contribution proportion are computed for each TC intensity class. Then, the mean quadrant distribution of rain rates along TC motion is analyzed. The result shows as follows. （1） TC mean rain rates increase with intensity class, and their radial distribution shows single-peak characteristic gradually. Moreover, the rain rates occurrence and contribution proportion change from dual-peak to single-peak distribution, with the peak rain rate at about 5.0 ram/h; （2） Stratiform rain dominate the rain type in the analysis zone, while convective rain mainly occurs in the eye-wall region; （3） The value of mean rain rate in each quadrant along TCs motion is close to each other relatively, and the maximum rainfall is located in the front quadrants, and minimum in the right-rear quadrant.