Weather system classification of local hourly heavy rainfall in Jiangxi Province

Abstract

Based on the conventional high-altitude and ground observation datasets and the 1-hour rainfall datasets from 93 national auto? matic weather stations in Jiangxi from April to September of 1998 to 2019, a total of 204 selected local hourly heavy rainfall events (hereinaf? ter LHR) in Jiangxi were analyzed and classified. With the analysis of synoptic meteorology, radiosonde, and physical properties, the concep? tual models of each category of these LHR events were established. The results are as follows. LHR in Jiangxi can be classified into 5 catego? ries, including Pre-Trough pattern (PRT), Post-Trough pattern (POT), Tropical System pattern (TS), Edge of Subtropical High pattern (ESH), and Control of Subtropical High (CSH) pattern. PRT is the most common type, which accounts for 48% of the total events. These events usual? ly occur in front of the high-altitude trough, near the mid-low-level shear lines, and are usually associated with cold fronts, stationary fronts, or low-pressure troughs on the surface. The second most frequent one is TS, which accounts for 19.1% of the total events. TS can also be divid? ed into the tropical cyclone type and the east wind wave type. The structure and movement of the tropical systems can significantly affect the area of LHR. ESH is divided into western ESH, southern ESH, and northern ESH. For this type, LHR events usually occur near the edge of the subtropical high 588 dagpm line, the low layer shear line, or the convergence line. CSH accounts for 5.5% of the total events. LHR happens when the subtropical high controls the entire Jiangxi Province. Particularly, when a center temperature at 500 hPa over the northern or eastern Jiangnan regions below -4℃ appears under the background of a cold trough, LHR events frequently occur on the ground convergence line, in the high-temperature area, or windward slope of mountains. POT is the least common type, which accounts for 4.4% of the events. It occurs under the northwesterly flow behind a trough, in the exit zone of the low-level jets, in the convergence zone, or on the surface convergence line.

Keywords

• hourly heavy rainfall
• synoptic type
• physical property
• conceptual model