Study on Process Event of a Meteorological Drought Comprehensive Index

Abstract

In order to understand the long-term evolution of meteorological drought in Chongqing， the localized revised meteorological drought comprehensive index （RMCI） of 34 national stations in Chongqing from 1960 to 2022 was used in conjunction with local standard for regional meteorological drought process evaluation to synchronously compare with the meteorological drought comprehensive index （MCI） process data from 1981 to 2020， then analysed the data structure and spatiotemporal distribution characteristics of the historical 63 a RMCI.The conclusion was as follows： （1） The cumulative frequency of the 40a RMCI single station process in Chongqing was 4.2% higher than that of MCI， and the frequency-intensity fitting of both showed a significant exponential distribution.The difference rate in the start time between RMCI and MCI single station processes was only 8.1%.The northeast of Chongqing was a consistently high incidence district of drought at all levels for RMCI and MCI single station processes， while the frequencies were relatively low in the central urban area， southwest， and middle districts.（2） The daily data of Chongqing's 63 a RMCI showed a normal distribution overall， with small（significant） differences in the distribution of mild， moderate， and severe drought（extreme drought） daily data across whole region and various districts.The daily data of RMCI severe and extreme drought in the central urban area was consistently relatively high and low compared to other districts， respectively.The frequency-intensity of RMCI single station process and regional process data were significantly inversely correlated， with the station-averaged frequency of mild， moderate， and extreme droughts for single station processes occurring in the western district of Chongqing being the highest， and the absolute range of extreme drought in regional process data was the highest， followed by moderate drought.（3） The intensity trends of RMCI single station and regional meteorological drought processes in Chongqing during the 63 a were not significant， but both showed a significant decreasing trend from 1962 to 2013.The overall weakening of both processes intensity in Chongqing after 2013 was related to the interdecadal decrease in high-temperature days since the 21st century.It could be considered that meteorological drought process events had complex interannual and interdecadal signals.The RMCI single station process events mainly exhibited periodic oscillations of 2~6 a and quasi-20 a， with the "drying out" of single station process events occurring in parts of Chongqing northeastern and southeastern districts being particularly significant.The RMCI regional process events exhibited periodic oscillations of 2~3 a， 4~6 a， and 8~12 a， with the highest frequency and strongest intensity of regional process events starting during the hot summer drought period and July， while the frequency and intensity of autumn drought period and December was relatively lowest and weakest， respectively.

Keywords

• meteorological drought
• rmci
• single station process
• regional process
• frequency
• intensity