一种气象干旱综合指数的过程事件研究

Study on Process Event of a Meteorological Drought Comprehensive Index

为掌握重庆气象干旱长时间序列演变规律,利用重庆1960-2022年34个国家站的本地化改进型气象干旱综合指数(RMCI)结合区域性气象干旱过程评估地方标准做气象干旱综合指数(MCI)1981-2020年同期对比,进而解析RMCI历史63 a数据结构及其时空分布特征。研究表明:(1)重庆40 a RMCI单站过程累计频次较MCI偏多4.2%,二者频次-强度拟合都呈显著的指数型分布,两者所有单站过程开始时间的差异率仅为8.1%;重庆东北部为RMCI和MCI单站过程各级旱情的一致高发区,而中心城区、西南部及中部地区发生频率相对较低。(2)重庆63 a RMCI日数据总体呈正态分布,全市及各分区轻旱、中旱、重旱(特旱)日数据分布差异较小(较大),中心城区重旱、特旱日数据较其他分区分别一致性偏大、偏小;RMCI单站、区域过程的频次与强弱都呈显著反相关,其中重庆西部发生轻旱、中旱、特旱单站过程的站均频次最多,而区域过程中特旱的极差绝对值最大、中旱次之。(3)63 a间重庆RMCI单站和区域气象干旱过程强度趋势都不显著,但1962-2013年却均为显著减小趋势,2013年后重庆过程强度的总体减弱与21世纪以来高温日数的年代际减少有所关联,气象干旱过程事件具有复杂的年际和年代际信号。RMCI单站过程事件主要存在2~6 a和准20 a的周期振荡,发生在重庆东北部偏东和东南部偏北地区的单站过程事件“变干”尤为显著;RMCI区域过程事件则存在2~3 a、4~6 a和8~12 a的周期振荡,开始于伏旱期及7月的区域过程事件频次最多、强度最强,而秋旱期和12月的频次相对最少、强度最弱。

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 syn‐chronously 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 Chongq‐ing was 4.2%higher than that of MCI,and the frequency-intensity fitting of both showed a significant exponen‐tial 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-in‐tensity 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 region‐al meteorological drought processes in Chongqing during the 63 a were not significant,but both showed a signifi‐cant 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 consid‐ered that meteorological drought process events had complex interannual and interdecadal signals.The RMCI sin‐gle 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 particu‐larly 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 relative‐ly lowest and weakest,respectively.