近40 a内蒙古冬旱时空演变特征

Characteristics of the spatial and temporal evolution of winter drought in Inner Mongolia over the past 40 years

冬季干旱是制约内蒙古冬季畜牧业生产的主要干扰因子之一,定量表征其时空变化特征和发展规律对防灾减灾、保障农牧业健康发展具有重要意义。利用1980—2021年冬季(10月—翌年3月)ERA5-Land再分析气象数据,计算1个月和6个月时间尺度的标准化降水蒸散指数(Standardized Precipitation Evapotranspiration Index,SPEI),采用趋势分析、时空热点分析等方法,分析内蒙古全区和五种主要植被类型区冬季干旱演变特征。结果表明:(1)近40 a内蒙古冬季整体SPEI呈现下降趋势,干旱化现象在不同植被和月份中表现不一,也有少数植被和月份趋于湿润化。(2)内蒙古地区冬季干旱的时空热点变化模式主要表现为:振荡的热点、振荡的冷点和未检测到模式。具体从季节和月时间尺度来看,冬旱热点主要集中在内蒙古中部和西部的大部分地区,以及东部的兴安盟和通辽市,即这些区域冬旱现象呈现加剧的趋势。(3)在干旱频率与频数统计方面,轻度冬旱事件发生频率最高,而荒漠草原和隔壁荒漠地区是发生冬旱事件最为频繁和严重的区域。

Winter drought is a main factor hindering winter livestock production in Inner Mongolia.Thus,quanti-tative characterization of its spatiotemporal changes and development patterns is of great significance for disaster prevention and reduction and for ensuring the healthy development of agriculture and animal husbandry.Using ERA5-Land reanalysis meteorological data from the winter of 1980 to 2021(October to March of the following year),the standardized precipitation evapotranspiration index(SPEI)was calculated at monthly and semi-annual scales.Trend analysis,spatiotemporal hotspot analysis,and other methods were used to analyze the winter drought evolution characteristics of the entire Inner Mongolia region and the five main vegetation types.Results show that in the past 40 years,the overall SPEI in Inner Mongolia has shown an increasing trend in winter,and aridification varies among different vegetation and months,with a few vegetation and months tending toward hu-midification.The change patterns in Inner Mongolia mainly include three types:oscillating hot spots,oscillating cold spots,and undetected patterns.From a seasonal perspective,hotspots are primarily distributed in most areas of western Inner Mongolia,as well as in Xing’an League and Tongliao City in the east.On a monthly scale,hot-spots often appear in the central and western regions of Inner Mongolia.With regard to drought frequency and fre-quency statistics,mild drought events have the highest frequency,whereas winter drought events occur more fre-quently and seriously in desert grasslands and neighboring desert areas.