基于游程理论和CWDI_(a)的农业干旱时空特征分析

Spatial and temporal characteristics of agricultural drought based on Runs Theory and crop water deficit abnormal index(CWDI_(a))

选用1960-2019年江苏省69个基本气象站逐日观测资料和全省旱灾资料,通过计算逐日作物水分亏缺距平指数,基于游程理论和小波分析等统计方法,分析农业干旱历时、频率、强度、范围的时空变化特征及其与干旱实际发生面积的关联度。结果表明:近60年全省平均年干旱日数变化范围是26~146 d,苏北、苏中、苏南年平均干旱日数分别为106 d、78 d、58 d,冬季干旱日数占年干旱总日数的比例最高,为32.3%,其次是夏季,中度干旱、重度干旱、特别干旱日数占近60年干旱总日数的比例分别为34%、29%、20%,苏北中度干旱、重度干旱、特别干旱60年平均发生频率分别为8.35%、6.50%、6.66%;干旱强度北强南弱,呈纬向分布,西北部旱情最重,也是最易发生极端干旱事件的地方;近60年中度干旱、重度干旱、特别干旱平均覆盖率分别为94.4%、83.0%、54.7%,21世纪10年代中度干旱及以上等级干旱发生范围最大;年干旱日数和干旱强度年际波动明显,无明显线性变化趋势,总体存在13~17年振荡周期;干旱历时长短和强度大小对实际受灾面积、成灾面积的影响不同,受灾面积与干旱日数的相关性更强,成灾面积与干旱强度的相关性更强。

Based on the daily observed data of 69 basic meteorological stations in Jiangsu province from 1960 to 2019 and drought data of the whole province,the temporal and spatial variation characteristics of agricultural drought duration,frequency,intensity and range and their correlation with drought area were analyzed by calculating the daily crop water deficit abnormal index and using the Runs Theory and wavelet analysis method.The results showed that,in recent 60 years,the average annual drought days in the whole province varied from 26 d to 146 d.The average drought days in northern,central and southern Jiangsu were 106 d,78 d and 58 d respectively.The proportion of drought days in winter was the highest(32.3%),followed by summer.The proportion of moderate drought days,severe drought days and extreme drought days accounted for 34%,29%and 20%of the total drought days in recent 60 years,respectively.The average frequency of moderate drought,severe drought and extreme drought in northern Jiangsu province were 8.35%,6.50%and 6.66%,respectively.The drought intensity was strong in the north and weak in the south,and was distributed in latitudinal direction.The drought was the most serious in the northwest,and the northwest was also the place most likely to occur extreme drought events.In recent 60 years,the average coverage rates of moderate drought,severe drought and extreme drought were 94.4%,83.0%and 54.7%,respectively.In the 10′s of the 21st century,the range of moderate drought and above was the largest.The annual drought days and drought intensity fluctuated obviously,and there was no obvious linear change trend.There was an oscillation period of 13-17 years.The influence of duration and intensity of drought on the actual affected area and disaster area was different.The correlation between affected area and drought days was stronger,and the correlation between disaster area and drought intensity was stronger.