Spatial and temporal characteristics and weather situation analysis of summer monsoon rainstorms in Yangjiang

Abstract The annual average rainfall of summer monsoon rainstorms in Yangjiang is highest in the southeast, decreasing towards the wings. Rainfall most frequently occurs in the early morning and around noon in June, with the western region experiencing the peak slightly earlier than other areas. Short-duration intense rainfall in the south occurs most frequently between 02:00 and 08:00, while in the north, it is more common between 08:00 and 14:00; the 6-hour accumulated rainfall ≥50mm most frequently occurs between 02:00 and 08:00. The weather situation conducive to monsoon rainstorms involves the stability of the South Asian high pressure at 200hPa over the Indochinese Peninsula, with Yangjiang at 500hPa ahead of the southern trough. During the early morning, the southwest monsoon strengthens from 925hPa over the northern Bay of Bengal to the northern South China Sea, pushing northward to Yangjiang’s land, creating the atmospheric conditions for monsoon rainstorms. Moisture primarily enters from the Indochinese Peninsula through the South China Sea, gradually increasing at night and reaching its peak from late night to early morning. The moisture channel and convergence height are below 700hPa. Atmospheric upward motion extends from the mid-to-upper levels to near the surface in the early morning, with the strong center moving from south to north.