一次层状云降水过程云中液态水含量的演变特征

The liquid water evolverment in a stratiform cloud-precipitation process

利用2011年7月3日甘南玛曲一次层云降水过程的地基微波辐射计探测资料,分析了玛曲强降水发生前后云中温度、湿度以及液态水含量在不同高度上随时间的演变特征:在降水开始前2小时左右,空中大气温度及相对湿度均随高度的升高而递减,云液态水含量为1.0g/m3出现急剧的增加累积;降水影响时,0℃层高度逐渐降低,空中大气冷却降温较快,温度随高度的增加出现了10～20℃/2km的递减,相对湿度随高度的升高而虽然也呈现递减规律,但8km高度以下的范围内,相对湿度比降水前有较大幅度的增加,尤其在4km高度处最为明显;而液态水含量的急剧减小过程,预示着降水即将出现消亡。指出了地面产生降水明显滞后于液态水含量的增加累积约40min,空中云液态水含量特别是低层液态水含量的累积厚度、持续时间和累积区顶层与底层有无明显的波动可判识层云地面产生降水的强弱。

The temporal evolvement characteristics of cloud temperature,humidity and liquid water content in different altitudes in a strong precipitation process were analyzed using the data detected by foundation of microwave radiometer on 3 July,2011 in Maqu.It was showed that with in about two hours before the precipitation start,the temperature and relative humidity decreased with the hight increasing,the content of cloud liquid water was 1.0g/m3 and aggrandized rapidly.When the rainfull started,the hight of 0℃ decreased and the atmosphere temperature was cool down faster;with the hight increasing,the temperature decreased in 10~20℃/2km.The relative humidity also decreased with the altitude increasing,but within the hight less than 8km the relative humidity increased rapidly than precipitation which was more distinct in the hight of 4km.The rapid decrease of liquid water content indicated the precipitation should be end. The time rain fall began was lagged about 40min far behind the cumulation of the liquid water content increasing.Cloud liquid water content,especially low-level liquid water content,was in good agreement with the distribution of surface rainfall intensity.The precipitation strength could be judged by the cumulative thickness,duration and bottom wave of cloud liquid water content.