Characteristics of the Variation of Upper-level Winds at Xisha,South China Sea
Using the daily data of 07:00 winds from an upper-level meteorological station at Xisha,South China Sea from 2007 to 2022,this paper analyzed the characteristics of wind direction and speed vari-ations for mandatory isobaric surface layers,maximum wind layers,zero-degree layers and the tropopause.The results are shown as follows.The wind directions of Xisha as detected by radiosonde at mandatory iso-baric surface layers are bimodal and their variations differ much with with the season.The wind direction is relatively concentrated for the layer of maximum wind,mainly at ENE.For Xisha,summer monsoons prevail at a time when the maximum wind layer occurs most frequently,being highly consistent in the time of occur-rence.The maximum wind layer at the upper level is mainly of the ENE wind and at heights between 15 000 and 16 000 m on average.Dominated by the WSW wind,the layer with zero degree of temperature has the lowest average air pressure and highest average altitude when the summer monsoon prevails.Historically,the layer between 150 and 40 hPa is the only layer for Xisha where a secondary tropopause occurs,at which the wind direction is mainly of ENE.At Xisha,the tropopause wind direction concentrates at ENE and the wind speed is the maximum when the summer monsoon is at its prime stage.
万方数据
维普
