基于常规气象观测资料和ERA5再分析数据,利用Barnes带通滤波法,借鉴计算地形阻挡气流上升高度的方法,对辽宁西部地区2021年6月下旬到7月中旬发生的两次暴雨过程(简称"6·27"暴雨、"7·13"暴雨)进行分析.结果表明:两次暴雨过程降水中心均位于北镇市,高空均有冷涡生成,下游高压脊阻挡冷涡东移,低空急流带来的暖湿水汽通过南边界流入暴雨区,975 hPa均存在风速辐合线和中尺度气旋式辐合中心.由于高空冷涡、下游高压脊、低空急流、对流不稳定强弱不同,以及975 hPa风速辐合线、中尺度气旋式辐合中心、850 hPa低空急流和地面中尺度辐合线的配置不同,导致"6·27"暴雨局地性强,降水时段集中,雨强偏大,而"7·13"暴雨影响范围较大,降水时段较分散,强降水维持时间长,雨强偏小.从雷达特征上看,降水最强时,"6·27"暴雨影响北镇的是低质心高效率降水回波,对流云区维持时间较长;"7·13"暴雨是高质心降水回波,对流云区维持时间较短,因此"6·27"暴雨雨强较大,北镇最大小时雨强达68 mm.
Comparison of Typical Characteristics of Two Heavy Rainfalls in Western Liaoning in 2021
Based on conventional meteorological observation data and ERA5 reanalysis data,the study analyzed two significant rainfall events that occurred in western Liaoning province from late June to mid-July 2021 by using the Barnes bandpass filtering method and established techniques to compute the ascent of terrain-obstructed airflow.The results showed that both events had precipitation centers situated in Beizhen city,accompanied by the development of cold vortexes at high altitudes.And the eastward movement of the cold vortex was hindered by a downstream high-pressure ridge.Conversely,warm and moist water vapor,transported by the low-level jet stream,entered the heavy rainfall area from the southern boundary.This region exhibited convergence lines of wind speeds at 975 hPa,along with mesoscale cyclonic convergence centers.Nonetheless,variations in the intensity of high-altitude cold vortexes,downstream high-pressure ridges,low-level jet streams,convective instability,and the configuration of convergence lines(wind speeds at 975 hPa),mesoscale cyclonic convergence centers,low-level jet streams(at 850 hPa),and mesoscale convergence lines(at the ground)contributed to the"6·27"heavy rain being more localized.This event experienced a concentrated precipitation period and higher rainfall intensity.In contrast,the"7·13"heavy rain had a broader impact range,a more dispersed precipitation period,a longer duration of heavy rainfall,and lower rainfall intensity.Based on radar characteristics,the"6·27"heavy rain in Beizhen displayed precipitation echoes with a low center of gravity and high efficiency during the most intense precipitation period.Additionally,it maintained convective cloud areas for a longer duration.But the"7·13"heavy rain exhibited precipitation echoes with a high center of gravity and a shorter duration of maintaining convective cloud areas.The above reasons resulted in a higher rainfall intensity for the"6·27"heavy rain.The maximum hourly rainfall intensity in Beizhen was 68 mm.
heavy rainfallBarnes bandpass filtermesoscale weather systemtopographical blockade
万方数据
维普
