青海东部城市群一次弱降雪漏报成因分析

Cause Analysis on Missing Report of a Snowfall in eastern Urban Agglomeration of Qinghai Province

利用MICAPS常规观测资料和ERA5再分析资料,诊断分析了2020年12月1日青海东部城市群一次弱降雪过程漏报成因,发现此次过程是低层充沛水汽条件配合中层弱垂直运动,在受地形影响的风场辐合抬升作用下产生的一次降雪。在高空系统不明显的客观条件下,预报员主观预报补充不足,缺乏对锋生、局地水汽条件和地形影响下的风场辐合、中尺度系统协调等方面的充分认识,是导致漏报的主要原因。同时,使用数值模式时,将24 h预报时效内的降水量消空量控制在0.1~0.2 mm,以降低降雪预报的不确定性。

Using MICAPS routine observation datasets and ERA5 reanalysis data on December 1,2020,omission causes about a weak snowfall event in eastern urban agglomeration of Qinghai province were diagnosed and analyzed,it was found that the snowfall produced by abundant water vapor condition with lower middle weak vertical movement,and the wind field convergence affected by terrain lifting.Under the objective condition of the unobvious upper-air system,the insufficient subjective judgment of forecasters that lacks the full understanding of frontogenesis,local water vapor condition,wind field convergence under the influence of topography,mesoscale system coordination and other aspects,compose the main reasons for the missing forecast.At the same time,the amount of precipitation cavitation during the 24-hour forecast is controlled between 0.1~0.2 mm when using the numerical forecast model,so as to reduce the uncertainty of snowfall forecast.