青藏高原零度层亮带的识别订正方法及在雷达估测降水中的应用  

Application of Bright Band Identification and Correction in Radar-Based QPE over Tibetan Plateau

作　　者：庄薇[1,2] 刘黎平[1] 胡志群[1] 

机构地区：[1]中国气象科学研究院灾害天气国家重点实验室,北京100081 [2]南京信息工程大学,南京210044

出　　处：《气象》2013年第8期1004-1013,共10页Meteorological Monthly

基　　金：国家重大基础研究(973)项目(2012CB417202);中国气象科学研究院基本科研业务费专项资金项目(大气水凝物微物理参数及风场垂直结构多波长遥感探测和反演方法研究);公益性行业(气象)科研专项(GYHY201006042);十一五国家科技支撑计划课题(2012BAC22BB00)共同资助

摘　　要：零度层亮带是指雪花或冰晶降落到零度层附近,表面发生融化而使雷达反射率突然增大的现象。它是影响雷达资料质量的重要因素,常会导致雷达估测降水的高估。青藏高原海拔高、零度层低,零度层以下的降水范围非常有限,亮带对青藏高原地区的雷达估测降水的影响更加显著。因此,对亮带进行自动识别订正,对提高青藏高原雷达降水估测的精度有重要意义。本文在考虑青藏高原遮挡严重的情况下,通过计算反射率垂直廓线来识别零度层亮带,对亮带区域进行订正,并将亮带订正前后的混合扫描反射率分别估测降水,分析亮带订正对降水估测误差的影响。结果表明:雷达识别的亮带高度在探空资料零度层以下几百米内;亮带订正前,反射率垂直廓线在零度层附近有显著弯曲,雷达对降水的估测明显偏高;亮带订正后,反射率垂直廓线在零度层附近的显著弯曲消失,雷达估测的降水量与雨量计的观测值较一致,降水估测误差比订正前明显减小。The bright band at 0℃ level is a phenomenon of sudden enhancement of the radar reflectivity due to the melting of snowflakes or ice crystals near the 0℃ isotherm. It is an important factor for the quality of radar data, often causing the over-estimation of precipitation. The altitude of Tibetan Plateau is high and the 0℃ level there is low, and the precipitation scopes under the layer are very limited, so the impact of bright band on the precipitation estimate of radar over the Tibetan Plateau is quite remarkable. There- fore, identifying and correcting the bright band automatically is of great significance to improve the preci- sion of radar-based quantitative precipitation estimation （QPE） over Tibetan Plateau. Consideri ng the seri ous blockage of radar beam over Tibetan Plateau, this paper identifies the 0℃ level bright band by calcu lating the vertical profile of refleetivity and corrects the bright band areas, using the hybrid scan reflectivi ty before and after the correction to estimate QPE respectively and analyzing the effect of bright band cor- rection on QPE errors. The results show that the height of the bright band from radar is usually severalcantly.

关 键 词：零度层亮带 反射率垂直廓线 青藏高原 降水 复杂地形 

分 类 号：P412[天文地球—大气科学及气象学]