榆林市不同等级干旱特征时空演变分析

Temporal-spatial Evolution of Drought Characteristics at Different Grades in Yulin

在气候变暖和人类活动加剧的双重背景下,榆林市干旱频繁发生,对该地区农业、生态环境和社会经济可持续发展产生了不利影响。尽管黄土高原干旱的负面影响已引起众多学者的关注,但是对榆林市干旱网格化和精细化的时空评估还有待研究。鉴于此,以榆林市为研究区域,基于逐月0.25°×0.25°空间分辨率的降水与土壤湿度SM资料,计算了3个月时间尺度下标准化降水指数SPI和标准化土壤湿度指数SSMI,采用游程理论进行干旱特征变量识别,并分析了不同等级干旱特征的时间演变特征和空间分布规律。结果表明:榆林市干旱形势严峻,在春冬季存在变湿趋势,夏季呈变干趋势,空间上,榆林南部地区有显著变干趋势;区域分别存在超过6个月的降水亏损及12个月的长历时土壤湿度亏损,出现降水亏损连续亏损月份早于土壤湿度亏损;干旱频次高值区域出现在榆林北部、南部以及东部边缘。研究结论可对榆林市干旱预防、社会生产及生态环境等具有重要意义。

Under the background of climate warming and human activities,Yulin city suffers from frequent drought,which has adverse effect on the agriculture,ecological environment and social economy in this area.Although the adverse effects of drought on the Loess Plateau have attracted the attention of many scholars,there is still a lack of grid and refined spatial and temporal assessment of drought in Yulin City.Therefore,taking Yulin City as the study area,based on the monthly precipitation and soil moisture data with a spatial resolution of 0.25°×0.25°,this paper calculates the standardized precipitation index(SPI)and the standardized soil moisture index(SSMI)on three month scales,identifies the drought characteristic parameters by the run theory,and analyzes the spatial-temporal evolution of drought characteristics at different grades.The results show that:The drought is rigorous in Yulin city.In time,a wet trend appears in spring and winter,while a dry trend in summer.In space,there is a significant dry trend in the southern of Yulin city.There are more than 6 months of long-term precipitation deficit and 12 months of long-term soil moisture deficit in Yulin City,respectively,and the month with consecutive precipitation deficit come earlier than the soil moisture deficit.Areas with high drought frequency are located in the northern,southern and eastern edges of Yulin.The conclusion is of great significance to the drought prevention,social production and ecological environment in Yulin city.