中国典型大范围持续干旱事件对大气环流的响应

Response of typical large-scale persistent drought events to atmospheric circulation in China

在全球气候变化和人类活动强度增加的双重驱动下,频繁、广发的大范围极端干旱事件给中国经济社会发展和生态环境造成了严重影响。为分析中国干旱的时空动态演变特征,该研究采用标准化降水蒸散指数(standardized precipitation evapotranspiration index,SPEI)结合干旱历时、干旱面积以及干旱烈度,构建了一种基于持续干旱栅格概念的大范围持续干旱事件识别方法,研究1961—2020年中国历史大范围持续干旱事件的时空动态演变特征及其对大气环流的响应机制。研究发现:过去60年中国共发生了47场大范围持续干旱事件,平均持续干旱历时为7.14个月,平均持续干旱面积为28.66%,平均持续干旱烈度为-2.86;1980—2010年间每10 a发生的干旱事件平均持续干旱面积出现连续扩大趋势,在1970—2020年间每10 a发生的干旱事件平均持续干旱历时集中在4~8个月之间;海洋尼诺指数(Oceanic Ni?o Index,ONI)与中国大范围持续干旱事件的发生表现出较强的相关性,ONI与SPEI3之间主要存在16~48月的共振周期,当强拉尼娜事件发生时会导致中国春季降水的减少,增加中国发生春旱的频次。研究结果有助于进一步理解中国干旱的成因和规律,提升防旱抗旱政策的科学性和精准性。

Frequent drought has posed widespread,large-scale and extremely severe impact on the ecological environment under global climate and human activities.This study aims to analyze the spatiotemporal dynamic evolution of drought in China.A threshold of-0.5 was chosen to identify drought conditions.A raster was set as the drought state at standardized precipitation evapotranspiration index(SPEI)less than-0.5.The start and end times of drought were varied for each raster within a single event,indicating the dynamic and evolving drought.At the same time,some rasters exited the drought states,while others entering.The contribution rates of drought to rasters were calculated at a given time,in order to capture the dynamic changes in drought.Three perspectives were considered:the extent of drought impact,duration,and severity.The SPEI was then used to assess the drought,in order to introduce the concept of persistent drought rasters.Large-scale and persistent drought events were identified to investigate the spatiotemporal dynamic evolution from 1961 to 2020,together with their response mechanisms to the atmospheric circulation.The research findings can be summarized as follows:1)A total of 47 events occurred between 1961 and 2020.The 1970s witnessed the highest frequency of large-scale persistent drought events,with 10 occurrences,while the 2000s and 2010s each experienced 9 such events.The average duration of these drought events was 7.14 months,with the longest average duration in the 1960s at 11.83 months.The average extent was 28.66%,with the highest average extent index reaching 33.75%in the 2000s.The average severity was-2.86 for the 47 large-scale persistent drought events.Between 1980 and 2010,the average area affected by persistent drought events each decade showed a continuous expanding trend.Between 1970 and 2020,the average duration of persistent drought events each decade was concentrated between 4 to 8 months.2)Before the 1990s,the lag time of Oceanic Niño Index's impact on spring precipitation was 3 and 9 months.From then on,the ONI's influence on summer and autumn precipitation extended to 6,9,and 12 months.Once La Niña events occurred,there was the decrease in the spring precipitation,thereby increasing the frequency of spring droughts in China.3)There was a resonance period of 16-48 months between ONI and SPEI3 during the years 1961-1976,1980-1988,1994-2001,and 2006-2020.The ONI index also demonstrated the strongest correlation with SPEI3 in this timeframe.While the WP index exhibited the weakest correlation with SPEI3 during the same periods.The research results help further understand the causes and patterns of drought in China,thereby enhancing the scientific basis and precision of drought prevention and mitigation policies.