一次阵风锋碰并作用触发短时强降水过程观测分析

对足够精细的观测资料做详尽的分析有助于澄清对流组织与增强的动力机制。本文利用机场跑道两端的分钟雨量资料、常规观测资料、加密自动站、ERA5再分析和S波段双偏振、X波段双偏振相控阵雷达资料，对2022年7月15日厦门机场出现的一次短时强降水天气进行了分析。结果表明：此次过程因阵风锋在传播过程中与地面辐合线交叉碰并而触发抬升，在500 hPa与850 hPa假相当位温差的负大值区和低层高温高湿的环境下激发出新的对流，给厦门机场带来罕见的短时强降水天气，期间分钟雨量最大达2.5 mm、跑道能见度降至400 m，两者呈反相关，但当分钟雨量大于1.6 mm时两者反相关性减弱，能见度谷值则晚于雨量峰值出现。观测分析表明，径向速度的气旋性切变与分钟雨量的变化趋势较为一致，两者有较好的对应关系。当2～5 km高度存在气旋性切变时雨量显著增加，当有两个高度层的切变强度达到2×10^-3s^-1以上时分钟雨量可达约2 mm，为本次短时强降水的组织特征。

Observation and Analysis of a Flash Heavy Rain Event Caused by Collision of Gust Fronts

Flash heavy rain and the resulting low visibility make it difficult for pilots to visually assess the runway clearly, severely impacting the take-off and landing of aircraft, thereby posing a threat to aviation operational safety. Moreover, the flight delays and diversions caused by this also result in significant losses for airlines and negatively affect socioeconomic benefits. Therefore, conducting comprehensive studies on flash heavy rain is crucial for ensuring aviation safety and enhancing flight punctuality. A thorough analysis of sufficiently detailed observational data is beneficial for clarifying the dynamic mechanisms of convective organisation and enhancement. On July 15, 2022, Xiamen Airport experienced a rare flash heavy rain event triggered by a weak background gust front. During this period, the precipitation intensity peaked at 2.5 mm per minute, and runway visibility rapidly decreased to 600 m, which is relatively uncommon at Xiamen Airport. To analyse this flash heavy rain event, this study utilises minute rainfall data from both ends of the runway, conventional observational data, densified automatic weather station data, ERA5 reanalysis, and S-band dual-polarisation and X-band dual-polarisation phased array radar data of Xiamen. The results of the study indicate that this event occurred under weak weather-scale forcing, where the gust front triggered uplift by intersecting and merging with the surface convergence line during propagation. In an environment characterised by negative large values of pseudo-equivalent potential temperature (θ_{se500-850 hPa}) and a warm and humid lower atmosphere, new convection was stimulated, resulting in the rare flash heavy rain at Xiamen Airport. During heavy rain, strong water vapour convergence appeared in the boundary layer at 1000 hPa. Minute rainfall on the runway showed an inverse correlation with visibility, but this correlation weakened when the minute rainfall exceeded 1.6 mm, and the visibility minimum lagged behind the rainfall peak by 7 minutes. Observational analysis reveals that the cyclonic shear of radial velocity was consistent with the trend of minute rainfall change. The peak minute rainfall at both ends of the runway corresponded to the peak cyclonic shear at a certain height layer, indicating a good correspondence between the two. When there was cyclonic shear in the radial velocity at heights of 2-5 km, rainfall significantly intensified. When the shear intensity at two height layers exceeded 2×10^-3s^-1, minute rainfall could reach approximately 2 mm (equivalent to an hourly rainfall of 120 mm), which emerged as a characteristic feature of this flash heavy rain event.