基于PRECIS的西北太平洋热带气旋生成情景预估

THE SCENARIO PROJECTION OF TROPICAL CYCLONE GENESIS OVER WESTERN NORTH PACIFIC USING(PRECIS)

利用全球气候模式ECHAM5的模拟数据驱动区域气候模拟系统PRECIS,产生西北太平洋SRES A1B气候情景数据。在模拟数据中分别采用三种热带气旋(TC)生成信息提取法,得出SRES A1B情景下1951—2050年的热带气旋生成模拟值,并分析不同热带气旋生成信息提取法对热带气旋生成的预估及其不确定性。结果表明:在气候基准时段(1971—2000年)下,对流年生成指数(CYGP)与热带气旋中心定位追踪识别法(TRACK)得出的TC生成气候平均态均接近观测值,而年生成指数(YGP)高于观测值;TRACK识别法得出的生成频数的年代际波动特征与实况相近;在未来2030 s预估时段(2021—2050年)下,CYGP指数与TRACK识别法的预估结果均显示未来TC生成数与基准时段相比呈减少趋势,而YGP指数的结果则显示未来逐年代的TC生成数与基准时段相比呈明显增加趋势。对各提取方法差异的初步分析结果表明,热力因子(包括海表温度、湿静力稳定度和对流降水等)是导致三种TC生成信息提取法预估不确定性的主要原因。

This study presents the future change of tropical cyclone（TC） genesis over Western North Pacific using the Providing Regional Climates for Impacts Studies（PRECIS） regional climate modeling system, which was driven by a Global Climate Model（ECHAM5） forced with the SRES A1B scenario. In PRECIS outputs, the TC genesis for the period from 1951 to 2050 was diagnosed by three methods： YGP（Yearly Genesis Parameter）, CYGP（Convective Yearly Genesis Parameter） and TRACK（locating and tracking individual TC centers）. In the baseline period（1971—2000）, the TC genesis climatology diagnosed by CYGP and TRACK both showed good agreement with observed TCs, while the YGP overestimated the TC genesis number. For the future period of 2021—2050, results from both CYGP and TRACK showed decreases of TC genesis number relative to the baseline period but YGP presented a significant increase. The preliminary analysis of discrepancies in extraction methods of TC genesis revealed that thermal factors, including sea surface temperature, moist static stability and convective precipitation etc., greatly affect diagnosed TC genesis thus introduced large uncertainties in future projections.