暴雨期间GNSS遥感气象要素的时序变化

Time series changes of GNSS remote sensing meteorological elements during rainstorms

针对暴雨短临预报准确率不高的问题,该文结合香港地区的暴雨实例,分析暴雨发生期间天气尺度特征和GNSS气象要素的时序变化特点及其各要素之间的相关性。研究结果表明:强烈的西南气流带来丰富水汽,高空强烈的辐散抽吸引起低层气压降低和对流运动的发展,配合中层低槽过境和低层冷空气南下,为暴雨发生提供条件;天顶对流层延迟变化的主要贡献来自大气水汽含量,可以用天顶对流层延迟替代大气水汽含量分析大气中的水汽累计及变化情况;暴雨发生前,气温较高,大气水汽含量和相对湿度时序增长快速,增长强度及其维持高水平状态的时长与后续雨量有较好的对应关系;大气水汽含量和相对湿度时序的上升分别反映了降水之前的充足水汽供应和水汽正在转向于饱和状态。

At present, the accuracy of short-term rainstorm nowcasting is not high. In this paper, a rainstorm happened in HongKong region was used as an instance to analyze its weather scale feature, characteristics of time series changes and their correlations of GNSS meteorological elements. The results showed that a strong south-west wind brought abundant moisture before heavy rain. The strong divergence and pumping in the upper level caused pressure reduction and development of convection in the lower level. In addition with the impact of middle level trough and cold air from the north, heavy rain occurred soon. The trends of precipitation water vapor（PWV）, zenith total delay （ZTD） and zenith wet delay（ZWD） were almost the same. PWV mainly influenced the changes of ZTD, so ZTD could be substitute for PWV to analyze the accumulation process and changes of atmospheric water vapor. Before the rainstorm, the temperature was higher, which inevitably led to increase of PWV and relative humidity（RH） series rapidly. Their growing velocity and time length of maintaining on a high level had a good correspondence to the subsequent precipitation. Before the precipitation happened, the increasing PWV reflected the sufficient supply of water vapor, and the growing RH revealed the phase inversion of atmospheric water vapor to its saturated state.