冬夏季环流隔季相关的数值试验

Numerical Experiment on the Interseasonal Connection of Circulation

利用海气耦合和大气气候模式研究东亚冬季风异常对夏季环流的影响,结果表明,东亚冬季风异常对于后期环流及海洋状态异常都起了很大的作用。一般情况下,强的冬季风与后期弱的东亚夏季风和较强的南海季风相对应。与强(弱)冬季风异常相关的风应力的改变可以使热带太平洋海温从冬季至夏季呈现LaNinna(ElNino)型异常分布。试验得到的由冬季风异常所产生的海洋及夏季环流的变化与实况是相当接近的。在异常的冬季风偏北风分量强迫下,西太平洋上形成的偏差气旋环流在夏季已不存在,这时东亚夏季风反而增强。而冬季赤道西风分量所产生的影响,则在西太平洋上形成显著的偏差气旋环流,使东亚副热带夏季风减弱,南海夏季风加强。对于东亚大气环流而言,与强弱冬季风对应的热带海洋海温异常强迫下,不仅是冬季,后期春季和夏季环流的特征都能得到很好的模拟。但是从分区看,西太平洋暖池区的海温异常比东太平洋更为重要。单纯的热带中东太平洋的海温异常对东亚大气环流的影响主要表现在冬季,对后期的影响并不十分清楚。整个热带海洋的异常型分布(不论是ElNino还是LaNina)型,对冬夏季风的影响是重要的,而单纯的某个地区的海温异常都比它的整体影响要小。从试验结果看,海温在大尺度冬夏季环流的隔季相关中起了十分重要的作用。

Based on numerical experiments of the Global Ocean\|Atmosphere\|Land System Model(CGCM) and the atmosphere general circulation model (LGCM) developed by State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), the influence of East Asian winter monsoon on the circulation of coming spring and summer is studied. Sensitivity experiments show that the anomalous East Asian winter monsoon plays a main role in interseasonal connection of circulation and SST anomaly (SSTA) distribution. Strong winter monsoon is accompanied by the posterior weak East Asian summer monsoon and strong South China Sea summer monsoon. Anomalous wind stress forcing of strong (weak) winter monsoon makes the tropical Pacific SSTA form La Nia (El Nio) pattern. Both the circulation and SSTA distribution forced by anomalous winter monsoon are in good agreement with the observed results. The northerly component of the winter monsoon anomaly makes the anomalous cyclone over the western Pacific not exist and the East Asian summer monsoon becomes stronger. The tropical westerly component over the winter monsoon anomaly makes the anomalous cyclone over the western Pacific form and the East Asian summer monsoon become weaker and the South China Sea summer monsoon stronger. The circulations over East Asia in winter and coming spring and summer are well simulated by the tropical SSTA effect in LCGM. Influence of the western Pacific warm pool SSTA is more important than the eastern tropical Pacific. The eastern tropical Pacific SSTA is favorable to the East Asian circulations in winter instead of coming seasons. The whole tropical SSTA pattern (El Nio or La Nia) plays a main role in winter and summer monsoons in comparison with the western Pacific warm pool or the eastern tropical Pacific SSTA. These results suggest that the sea surface temperature plays an important medium role in interseasonal connection.