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采用标准化降水指数(SPI)为干旱指标,计算了山西省运城市49年(1958—2007年)各月干旱指数,并在此基础上分析了山西南部地区季节性干旱特征。研究表明,干旱强度与干旱频率在不同年代际表现特征不同。与运城地区49年同期均值相比,进入20世纪90年代后,春旱发生频率、干旱强度分别提高了29.0%、5.1%;夏旱发生频率提高41.9%,干旱强度下降了7.4%;秋旱发生频率下降了23.8%,干旱强度提高了7.7%;冬旱发生频率下降了26.6%,干旱强度下降了37.5%。干旱的季节性特征为春旱和夏旱有加重趋势,秋旱和冬旱有减弱趋势。春旱(3—5月)和伏旱(7—8月)作为可预见性干旱,可采用土壤墒情监测、干旱预警、制定系统性抗旱措施等综合防御技术。对于不可预见类型干旱,可采用建立抗旱水源、储备抗旱机械等策略。
Using the standardized precipitation index (SPI) as the drought index, the monthly drought index of Yuncheng City in Shanxi Province for 49 years (1958-2007) was calculated, and on the basis of this, the seasonal drought characteristics in southern Shanxi were analyzed. Studies have shown that drought intensity and drought frequency are different in different decadal characteristics. Compared with the 49-year average of Yuncheng area, the frequency and intensity of spring drought increased by 29.0% and 5.1% respectively after entering the 1990s; the frequency of summer drought increased by 41.9% and the drought intensity decreased by 7.4%; autumn drought The occurrence frequency decreased by 23.8%, the drought intensity increased by 7.7%, the frequency of winter drought decreased by 26.6% and the drought intensity decreased by 37.5%. The seasonal characteristics of drought are aggravating in spring drought and summer drought, with a decreasing trend in autumn and winter drought. Spring drought (March-May) and summer drought (July-August) As a predictable drought, integrated defensive techniques such as soil moisture monitoring, drought warning and the development of systematic drought control measures can be used. For the unforeseen type of drought, we can adopt such strategies as establishing drought-resistant water sources and reserving drought-resistant machinery.