Abnormality of the monsoon wind in the sea area along the southeasterncoast of China and the response of the northern areaof the South China Sea during the ENSO events

-Variations of monsoon wind field in the sea area along the southeastern coast of China during the ENSO events and its influence on the sea level and sea surface temperature (SST) are explored mainly on the basis of the data of monthly mean wind at 850 hPa and five coastal stations during 1973-1987. The results from the analyses of the data and theoretical estimation show that the southwest wind anomalies appeared in the study area during the events, and northeast wind anomalies occurred in general before the events. With the coastline of the area being parallel basically to the direction of the wind, an Ekman transport will result in an accumulation of the water near the coast or a departure of the water from the coast. As a result , the sea level and SST there will be affected markedly. During the events, southwest wind will intensify in the summer, and northeast wind will weaken in the winter. Their total effect is that a large negative anomaly of the sea level and SST will occur. The estimations indicate that the monsoon wind is stronger in the summer and weaker in the winter than the normal by 1-1. 5 m/s during the events, and this anomaly will cause a decrease of the sea level by 7-11 cm . Changes of the wind field, therefore, is mainly responsible for a large negative anomalies of the sea level and SST there during the ENSO events.

卫星观测的我国近海海域闪电分布特征

利用星载闪电探测仪OTD(optical transient detecter)和LIS(lightning imaging sensor)所获取的1995年6月—2006年4月的卫星闪电资料,结合NOAA Optimum Interpolation SST海温资料,分析我国近海海域的闪电分布时空特征以及闪电活动与该海域海温之间的相关性。结果表明:我国近海闪电密度平均值为3.39 fl·km^(-2)·a^(-1),其中,南海和渤海的闪电活动相对频繁,随着与海岸线间距离以及纬度的增加,该海域闪电密度逐渐下降;在春季和冬季,黑潮主干海域的海温值相对较高,该处闪电活动也明显强于同纬度的东海近海和太平洋海域,表明黑潮海域是强闪电活动区;在季节变化上,我国近海海域闪电活动与同海域海温呈明显正相关,相关系数达0.797,闪电活动与海温变化体现出了一致的变化趋势;而在年际变化上,我国近海海域闪电活动与该海域海温的线性相关不显著,说明我国近海海域海温的年际变化并不是引起该海域闪电活动年际变化的主要原因。