Gaoyuan qixiang (Aug 2023)
Characteristics of Short-Time Heavy Rainfall in the Sichuan Basin based on High-Density Station Observations
Abstract
The short-time heavy rainfall is sudden and easy to cause disaster， which poses a great threat to people's life and property safety.This paper analyzed the spatial and temporal variation characteristics of short-time heavy rainfall （≥20 mm·h-1） in the Sichuan basin and its relationship with geological hazards.The hourly precipitation observation data from high-density regional automatic stations and national stations （1688 stations） was used from 2011 to 2020.The results showed that： （1） The large values of short-time heavy rainfall frequency and rainfall were mainly concentrated in the transition area between high mountains and basins in the southwest and along the Longmen Mountains in the northwest， with more in the west and less in the east overall.（2） The frequency and rainfall were increasing， but the intensity and intensity extremes were decreasing， so the increase in rainfall was caused by the increase in frequency.In the northwestern part of the basin， the frequency and rainfall was the highest， and the interannual variability was the strongest.（3） The short-time heavy rainfall occurred from March to October， one month earlier than in the early 21st century.The frequency peaked in July and was concentrated from 23:00 to 07:00 next day （Beijing Time）， accounting for 56.5% of the whole day.The basin as a whole exhibited a single-peak night rain structure， but the northwestern， northeastern and central parts were bimodal， and the peak time was delayed from south to north.（4） The correlation and composite analysis revealed that the number of geological hazards was highly correlated with the frequency and rainfall of short-time heavy rainfall in the northwest， with correlation coefficients of 0.87 and 0.89， respectively.For the Sichuan basin as a whole， landslides and debris flows showed significant differences between the more frequent and less frequent short-time heavy rainfall.In the northwestern and southwestern parts of the basin， the short-time heavy rainfall had a large impact on various geological hazards.In the northeast， it had an impact on landslides， debris flows and other geological hazards， while in the south， it had an impact on other types of geological hazards.The northwest and northeast had the highest number of geological hazards， accounting for 40.2% and 31.7% of the total， respectively.But the short-time heavy rainfall was more likely to cause casualties in the northwest， and mainly caused direct economic losses and injuries in the northeast.The number of geological hazards in Sichuan basin was increasing， while the economic loss was decreasing， indicating that the disaster prevention and mitigation capacity has been significantly improved.
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