| Extreme precipitation events are seriously disaster-causing,and Henan Province,as a province with large population,agriculture and transportation,needs to carry out research on fine forecasting techniques for extreme precipitation to provide a reference basis for forecasting and warning of such catastrophic weather,which is of great significance for disaster prevention and mitigation.In this paper,the spatial and temporal distribution characteristics and weather background characteristics of extreme hourly precipitation in Henan Province during warm seasons from 2010 to 2018 are studied.This is divided into two parts.The first part analyzes the spatial and temporal distribution characteristics of extreme hourly precipitation in Henan Province and the differences of extreme hourly precipitation in different sub-surfaces using hourly precipitation data from 371 meteorological stations(including 122 national stations and249 regional backbone stations)in Henan Province from May to September 2010-2018.In the second part,the above precipitation data and ERA-interim reanalysis data are used to study the weather situation characteristics of extreme hourly precipitation and the distribution characteristics of environmental physical elements in Henan Province.The major findings are summarized as follows:(1)The high value areas of the 99.9th percentile extreme hourly precipitation indicators(frequency,intensity,contribution rate)in Henan Province are mainly located in the southern part of Funiu Mountain,the eastern part of the Huanghuai Plain and the southwestern part of the Huai River Basin;extreme hourly precipitation events largely occur in July and August,with more than 1/4 of them being regional extreme precipitation events;the diurnal variation of the extreme hourly precipitation frequency is obviously bimodal,where the main peak occurring at 17:00 p.m.and the secondary peak at 01:00 a.m..By contrast,a multi-peak pattern is observed in the daily variation of the extreme hourly precipitation frequency above 80 mm·h-1.The main peak is found at 01 a.m.in the morning with a more prominent night-occurrence.(2)The extreme hourly precipitation characteristics of different underlying surfaces are different:urban extreme hourly precipitation has the highest intensity,lowest frequency,and lowest contribution rate,whilst mountain extreme hourly precipitation has the lowest intensity and highest frequency,and hilly extreme hourly precipitation has the highest contribution rate.Four types of underlying surface extremes,despite the diurnal changes of hourly precipitation,all present the characteristics of double peaks,whose differences are:in mountainous areas,the peak at night is dominant,and the peak in the afternoon is supplemented;in hilly areas,the peak at night co-exists with the peak in the evening,sharing similar strengths;the afternoon peak dominates in plains and urban areas,accompanied by a weak night peak.But the afternoon peak in urban areas is stronger and lags in plain areas.(3)There are three types of weather conditions in the extreme hourly precipitation process,which are the edge of the subtropical high,the northwesterly airflow type and the low trough type.The statistics shows that the edge-convergence and low vortex types of the subtropical high mainly appear in July and August,and the most frequent occurrences are in July;the northwestern airflow type appears most frequently in June.(4)The necessary atmospheric precipitable water(TPW)for the three levels of extreme hourly precipitation(Class I:20 to 49.9 mm·h-1;Class II:50 to 79.9 mm·h-1;Class III:80 mm·h-1 or more)are:26.9 mm,30.8 mm,and 39.7 mm respectively,and more than 50%occur in humid environments with TPW?60 mm;more than 50%of those three levels occur in environments with CAPE values between 300 J·kg-1 and1500 J·kg-1 and temperature differences between 850 h Pa and 500 h Pa between 20 and26°C;about 75%of the three levels occur in favorable large-scale convergent lifting environments;TPW values may be indicative of the intensity of extreme hourly precipitation. |
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