基于标准化降水蒸散指数的陕西省近50 a干旱特征分析

基于陕西省18 个气象站点1961-2010 年实测气象资料,利用标准化降水蒸散指数(SPEI),通过计算各站历年逐月的SPEI 指数值,统计近50 a 各站点出现的干旱过程,分析了陕西省历年、历年各季及月尺度上的干旱发生频率、覆盖面积和干旱发生强度,揭示了陕西省干旱发生的时空和强度演变特征。研究结果表明,近50 a 来陕西省干旱发生频率呈明显的增长趋势,尤其是1990 年以来的近20 a;陕西省在年、春、夏、秋、冬及月尺度上均有干旱发生。其中,秋季干旱最为严重,春季次之。在年代际变化方面,全省以20 世纪90 年代干旱最为严重,2000 年以来的干旱次之;干旱出现既有全省性的大范围干旱,也有区域性的局部干旱,分布极不均匀,总体分布特征是北多南少;干旱发生强度分布呈现出关中最强、陕南次之、陕北最弱的特点。

Analysis of Drought Characteristics of Shaanxi Province in Recent 50 Years Based on Standardized Precipitation Evapotranspiration Index

Drought disaster is one of the main natural disasters in Shaanxi Province, suffering from it often "nine out of ten years". It impacts the people's daily life and social production to different extent. In this paper, the observed meteorological data of 18 meteorological stations from 1961 to 2010 in Shaanxi Province were collected and the standardized precipitation evapotranspiration index (SPEI) was used. Based on the monthly SPEI values of each station in recent 50 years, the drought processes of each station were confirmed one by one and the occurrence frequencies, scopes and severities of the meteorological droughts were computed and the annual, seasonal and monthly drought occurrence frequency, coverage and intensity over years were analyzed, and the spatial and temporal evolution and the intensity of drought occurrence of the province were revealed. Research results show that there was an obviously growing trend in frequency of drought in recent 50 years, especially in recent 20 years since 1990; drought occurred without exception in the annual, spring, summer, autumn, winter and monthly scales. Among them, the most serious drought occurred in autumn and spring. In decadal variability, the province witnessed the worst drought in the 1990s, next since the year 2000; drought in Shaanxi was either widespread throughout the province or locally, with quite uneven distribution regionally, the overall distribution characteristics are more in the north and less in the south; the strongest drought distribution intensity presented in Guanzhong of Shaanxi, followed by southern Shaanxi and northern Shaanxi is the weakest.