1961—2020年黄土高原地区气象干旱时空演变特征研究

Temporal and Spatial Evolution Characteristics of Meteorological Drought in the Loess Plateau from 1961 to 2020

基于黄土高原地区61个气象站点1961—2020年的逐日气象资料,探究该研究区域的历史干旱演变特征。采用标准化降雨蒸散指数(SPEI),运用Morlet小波分析、干旱面积覆盖率、干旱发生频率和Mann-Kendall突变检验等研究方法,揭示近60 a全球变暖背景下黄土高原地区的干湿变化特征及周期特征,并对干旱进行归因分析。研究结果表明:SPEI值的干湿交替变化具有全域性,年度SPEI_12和春、秋、冬季SPEI_3在研究时段呈逐年下降趋势,干旱倾向趋势降幅排序为秋>春>冬>年,夏季SPEI_3呈现相对平缓的升高趋势,趋势率为0.02/10a;干旱覆盖面积整体呈上升趋势不显著,年干旱频率在31.40%和35.15%之间,中西部区域站点干旱化趋势较大;不同时间尺度的干湿变化周期不稳定,目前正处于并长期处于偏暖湿化阶段。目前的暖湿化趋势仅体现为量的变化,并不足以改变该区域的基本气候状态,其仍处于温凉干燥的干旱与半干旱气候范围。

Based on the daily meteorological data of 61 meteorological stations in the Loess Plateau from 1961 to 2020,this paper explores the historical arid evolution characteristics of the study area.The paper adopts the standardized precipitation evapotranspiration index(SPEI),Morlet wavelet analysis,drought area coverage,drought frequency,and Mann-Kendall mutation test to reveal the characteristics of dry and wet changes and cycle characteristics of the Loess Plateau under the background of nearly 60a global warming.Meanwhile,it carries out the attribution analysis of drought.The results show that the alternating wet and dry variation of SPEI values is region-wide.Annual SPEI_12 and spring,autumn,and winter SPEI_3 show a decreasing trend year by year during the study period,and the decreasing trend of drought tendency is ranked as autumn>spring>winter>annual.Summer SPEI_3 shows a relatively flat increasing trend with a trend rate of 0.02/10a.The overall drought coverage area shows an upward trend,and the annual drought frequency is between 31.40%and 35.15%.The aridification trend of the central and western regions is large.The cycle of dry and wet changes at different time scales is unstable,and it is currently in the stage of warm and humidification for a long time.The current trend of warming and humidification is only reflected in quantitative changes,which is not enough to change the basic climatic state of the region and is still in the arid and semi-arid climate range of cool and dry.