摘要
本文利用地球流体力学实验室(GFDL)的低分辨气候模式进行数值试验,以研究海温异常对台风形成的影响.试验采用恒定8月气候条件和海表温度(SST).海温异常(SSTA)被置于北太平洋不同区域.结果表明,台风生成频率在暖SSTA区明显增加.这是由于暖SSTA区低层辐合的增强一方面使低空气旋式环流和高空反气旋式环流加大,另一方面导致低层水汽向该区辐合,使潜热释放加强,对流加剧所致.此一机制被用于解释台风频率和ENSO事件的相关.在冷ENSO年份,西北和西南太平洋台风增多不仅是由于赤道东太平洋SST异常冷,还与西太平洋SST异常暖有关.
Numerical experiments based upon a low resolution version of the GFDL climate model were developed to investigate the sensitivity of tropical storm (TS) formation to sea surface temperature (SST) anomaly. Perpetual August climate was specified, and the mean August SST was prescribed for the model. SST anomalies (SSTAS) were placed in different parts of the tropical North Pacific Ocean. The frequencies of tropical storm formation over the western North Pacific were counted in the different experiments and used for the sensitivity study.It was shown that the frequency of TS formation is very sensitive to the underlying SST. Significant increases in the frequency of TS formation were found over the warm SSTA region. The mechanism linking the TS formation to SSTA was investigated. It was found that the primary atmospheric response to a given SSTA is the low level convergence over warm SSTA region and divergence over cold SST regions. This large- scale pattern causes cyclonic vorticity generation in the lower troposphere and anticyclonic vorticity generation in the upper troposphere over the regions of positive SSTA, resulting in lower level water vapor flux convergence in that region to reinforce the latent heat energy for the development of convection. More TSs are then formed over the warm SSTA region. These mechanisms were used to link the variation of TS formation frequency to ENSO events. During cold ENSO years, more TS formation occurs over the regions of the western North Pacific and western South Pacific not only because the SST in the eastern equatorial Pacific is colder than normal, but also because the SST in the western Pacific becomes warmer than normal.
出处
《大气科学》
CSCD
北大核心
1992年第3期322-332,共11页
Chinese Journal of Atmospheric Sciences
关键词
海温
异常
台风
形成
Sea surface temperature anomaly, Low level convergence
Typhoon.
