基于星载测雨雷达2004-2014年观测的川渝地区降水垂直结构的气候特征

Variability in the vertical structure of precipitation in Sichuan and Chongqing based on 2004-2014 space-borne observations

中文关键词:  星载雷达  天气雷达  降水  气候态反射率垂直廓线

英文关键词:Space-borne radar  Weather radar  Precipitation  Climatological VPR

中文摘要:

      使用热带测雨卫星（TRMM）搭载的测雨雷达（PR）2004-2014年长达11 a的连续观测资料对青藏高原东南缘川渝地区不同季节不同降水类型的垂直结构特征进行了统计分析，并建立了相应的气候态反射率垂直廓线（Vertical Profiles of Reflectivity，简称VPR）。结果表明，由于不同的微物理及动力过程，降水类型对反射率垂直廓线的结构特征影响很大，90%的层云0℃层亮带峰值强度低于32 dBz，50%的对流云最大反射率强度超过35 dBz。降水类型及强度均对反射率垂直廓线的形状影响很大，层云系统发生中及大雨时其冰雪区的聚合反应效率明显较发生小雨时高。反射率垂直廓线特征参数具有一定的区域性和季节特征，且地表加热和地形高度的作用会加强上升气流对反射率垂直廓线形态的影响，上升气流的强度影响着冰雪及雨水区的碰并增长率以及低层的蒸发作用，从而进一步影响低层雨区的反射率垂直廓线斜率，边界层的相对湿度是另一个影响雨区反射率垂直廓线斜率及蒸发率的重要因素。星载测雨雷达的云分类算法在青藏高原东南缘地区受到一定的挑战，仍有改进的空间；未来可以将基于星载测雨雷达建立气候态层云典型反射率垂直廓线应用于联合地基天气雷达网观测以弥补后者在复杂地形条件下探测范围及能力受限的缺陷，从而改进雷达定量降水估测的误差。

英文摘要:

      This study presents a statistical analysis of the variability of vertical precipitation structure in the eastern downstream region of the Tibetan Plateau (TP) based on measurements by the precipitation radar (PR) onboard the National Aeronautics and Space Administration (NASA)'s Tropical Rainfall Measuring Mission (TRMM) satellite. Data over an 11-year time span (Jan 2004-Dec 2014) are analyzed. The results reveal the seasonal and spatial variability of the storm height, the freezing level, and the bright-band for different types of precipitation as well as the characteristics of intensity-related and type-related vertical profiles of reflectivity (VPR). Major findings are as follows. Precipitation types greatly impact the VPR in terms of their different microphysical and dynamical processes. About 90% of the bright-band peak reflectivity of stratiform precipitation are less than 32 dBz, and 50% of the maximum reflectivity of convective precipitation exceed 35 dBz. The intensity of surface rainfall rate also depends on the shape of the VPR. For stratiform precipitation, ice-snow aggregation is faster during moderate and heavy rainfall than that in light rainfall. Both surface heating and terrain impact the VPR shapes and their respective rain region slopes by changing the updrafts, which may affect the ratio of collision-coalescence as well as the low-level evaporation. Overall, the findings indicate that the developed representative Ku-band VPR can be used to improve surface precipitation estimates in regions with complex terrain, where ground-based radar has limited visibility at low levels.