夏季青藏高原深厚及浅薄降水云气候特征分析

Analysis on Climatological Characteristics of Deep and Shallow Precipitation Cloud in Summer over Qinghai-Xizang Plateau

利用1998-2007年热带测雨卫星TRMM搭载的测雨雷达PR和可见光/红外扫描仪VIRS的融合资料,研究了夏季青藏高原深厚降水(深厚强对流和深厚弱对流)及浅薄降水的水平分布、垂直结构及红外信号特征,并对其日变化特点和降水的经向移动特征进行了分析。结果表明,夏季高原降水主要以深厚弱对流降水为主(67.8%),浅薄降水次之(26.4%),深厚强对流降水出现最少(5.8%)。不同云顶红外辐射温度的平均降水廓线表明,深厚降水从雨顶高度至近地面高度均经历先增大后减小的过程,而浅薄降水只有增大过程。深厚强对流和深厚弱对流的降水频次峰值均出现在16:00(地方时,下同),降水强度峰值分别出现在18:00和13:00,其中深厚强对流降水强度在00:00还出现次峰值。浅薄降水的降水频次及强度峰值均出现在20:00,呈现夜雨特点。深厚降水和浅薄降水的云顶红外辐射温度日变化特征相似,最低值均出现在19:00。深厚强对流和深厚弱对流降水具有明显的东移特征,其中深厚弱对流降水的东移特征更为明显,而浅薄降水无明显的经向传播特征。

Climatological characteristics of the deep(strong deep convection and weak deep convection),shallow precipitat ionincluding their horizontal distribution,vertical structures,infrared signal characteristics,the diurnal variation and meridional movement of the precipitation mentioned above in the Plateau(QX) are investigated based on combining measurements of the tropical rainfall measuring mission(TRMM) precipitation radar(PR) and visible and infrared scanner(V1RS) from 1998 to 2007.The results show that the precipitation over QX is mainly in the form of week deep convection,which occupies 67.8%followed by the form of shallow precipitation with 26.4%and the strong deep convection with 5.8%.The average rain rates of deep precipitation for different cloud infrared radiant temperature all experience an increasing-reducing process from the storm top altitude to the ground level,while the shallow precipitation only has anincreasing process.Both the precipitation frequency peaks forstrong deep convection and weak deep convection appear at 16:00(local time,hereafter the same).While the precipitation intensities of which reach their peak at 13:00 and 18:00,respectively.Moreover,the strong deep convection has a secondary peak at 00:00.For the shallow precipitation,the precipitation frequency and intensity peaks both appear at 20:00,having the characteristicof night rain.The diurnal variation curves of radiant temperatureof deep and shallow precipitation are similar to each other,as a result,their minimaappcar around 19:00.It is obvious that the strong deep convection and weak deep convection have the characteristics of eastward movement,and the week deep convection is more obvious.The shallow precipitation don't have significant meridional propagation characteristics.