基于多普勒天气雷达的垂直散度和温度平流廓线反演

Retrieving Vertical Divergence and Temperature Advection Profiles from Doppler Weather Radar Data

垂直散度廓线可用于推断大气垂直运动情况,垂直温度平流廓线可用于推断大气层结是否稳定,有助于预报员推断本站降水演变趋势。鉴于我国多普勒天气雷达中还没有垂直散度和温度平流廓线产品,提出了这两种产品的反演方法。首先使用分层VVP方法从雷达体扫径向速度资料中反演出雷达站上空的垂直风廓线和垂直散度廓线,然后在假设大气处于地转平衡条件下,基于温度平流与地转风随高度的变化关系,从垂直风廓线中反演出垂直温度平流廓线。以两次大范围暴雨天气过程为例,反演了雷达站上空的垂直风廓线、散度廓线和温度平流廓线,并对反演结果进行了分析。结果表明:在雷达周围有大范围降水回波的情况下,使用分层VVP方法能合理地反演出雷达站上空的垂直风廓线和散度廓线;在这种情况下,反演的垂直风廓线代表各个高度雷达有效探测范围内的平均水平风,可近似满足地转平衡条件,因此,使用热成风方程能较为合理地从垂直风廓线中反演出垂直温度平流廓线;三个反演产品的合理性可用天气学理论和天气实况来解释。

Divergence and temperature advection can be used to infer the atmospheric vertical movement situation and the stability of atmospheric stratification respectively,which is helpful to deduce the precipitation evolution trend.Considering there is no vertical divergence profile and vertical temperature advection profile products of China new generation weather radar,this paper proposes the retrieval algorithms of vertical divergence and temperature advection profiles from Doppler weather radar data.First,the vertical wind profile and vertical divergence profile above the radar station are retrieved using layered VVP method from radar radial velocity data,and then under the assumption that the atmosphere were in the geostrophic balance in middle latitude and based on the relationship between the temperature advection and geostrophic wind changing with height,the vertical temperature advection profile is retrieved from the vertical wind profile.Taking two severe precipitation processes as examples,the retrieved vertical wind profile,vertical divergence profile and vertical temperature advection profile are analyzed.The results show that the vertical wind profile and vertical divergence profile can be retrieved reasonably using layered VVP in the case of large-scale precipitation around radar.In this case,the retrieved winds represent average winds within the valid detection range of radar,which meets approximately the geostrophic equilibrium condition,so the vertical temperature advection profile can be retrieved reasonably from the vertical wind profile.The synoptic principles and the observation data can be used to explain the reliability of the retrieval results.