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Statistical Characteristics and Synoptic Situations of Long‐Duration Heavy Rainfall Events Over North China

机译:华北地区统计特征与长期大雨事件的概要情况

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The spatiotemporal characteristics of long‐duration heavy rainfall (LDHR) events are statistically analyzed using hourly surface observations over central‐southern North China during the warm seasons of 2011–2018, revealing pronounced variabilities in the frequency and amount of LDHR. Two accumulated rainfall peaks are found in the western (WHRR) and eastern (EHRR) regions of central‐southern North China. The LDHR occurrence frequency decreases westward, and the peaks of the LDHR amount, frequency and intensity in the WHRR and EHRR are observed at nighttime (2100–0200?Beijing Standard Time) or in the early morning (0300–0700?Beijing Standard Time). The rainfall amount exhibits a bimodal diurnal variation in the WHRR (determined mainly by the rainfall intensity), whereas a single rainfall frequency‐related peak is found in the EHRR. Four types of LDHR events corresponding to different flow patterns, synoptic systems, and moisture transport mechanisms are classified according to their locations. The first is heavy rainfall in the WHRR with an upper‐level jet favorable for an ascending motion near Taihang Mountain; topographic blocking of southerly flow is crucial for heavy rainfall formation. The second describes heavy rainfall in the EHRR attributable to the favorable configurations of upper‐ and lower‐level systems. Heavy rainfall occurs over both the WHRR and the EHRR in the third type, including topographic blocking and convergence associated with low‐pressure systems or shear lines and a mesoscale low vortex or shear line related to topographic effects and positive vorticity advection in front of a westerly trough. The fourth shows a scattered distribution of LDHR stations and is generally not comparable to the first three types.
机译:在2011 - 2018年温暖的季节期间,使用每小时表面观察,在2011 - 2018年的温暖季节,在南方华北地区的每小时表面观测,在统计上分析了统计学分析的时空特点,揭示了LDHR频率和数量的明显变形。两种累计的降雨峰是在华北南部的西部(WHRR)和东部(EHRR)地区发现的。 LDHR发生频率向西减少,WHRR和EHRR中的LDHR量,频率和强度的峰值在夜间(2100-0200?北京标准时间)或清晨(0300-0700?北京标准时间) 。降雨量在WHRR(主要由降雨强度决定)上表现出双峰差变化,而在EHRR中发现了单次降雨频率相关的峰。根据其位置对应于不同流动模式,天气系统和水分传输机制的四种类型的LDHR事件。第一个是大量的降雨,在太空山附近的上级喷射有一个升高的运动;南部流动的地形阻挡对于大雨形成至关重要。第二个描述了ehrr中的大量降雨,其归因于上层和下层系统的有利配置。在第三种类型的WHRR和EHRR中发生大量降雨,包括与低压系统或剪切线相关的地形阻塞和收敛以及与与西方的地形效果和正涡度平流相关的Mescle低涡流或剪切线。槽。第四示出了LDHR站的散射分布,并且通常与前三种类型不相当。

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