论文部分内容阅读
[目的]分析研究了西北地区历次特大干旱的开端-宁夏西吉县干旱暴雨等极端天气气候事件的变化规律。[方法]用降水距平百分率划分干旱等级并进行统计分析;用季节指数、线形趋势、5年滑动反映干旱变化趋势;时间序列的循环波动用多项式模拟年代际尺度变化,多项式分解的正数部分用柱形图模拟年际尺度变化。[结果]11～6月干旱季节指数大且波动变化;年干旱的总变化趋势呈上升,年代际尺度的干旱以1977年前后最为严重,有约15年、20年的周期,年际尺度的干旱近年急剧上升;对3～5月、9～11月干旱的总趋势、年代际尺度、年际尺度的变化进行了分析讨论。从500hPa高空天气图上对西吉第一场透雨、久旱转雨天气形势进行了归类分型。[结论]这些工作对开展干旱防灾减灾具有重要的参考价值。
[Objective] The research aimed to analyze and study the changes of the extreme weather and climate events in the northwestern region, such as arid rainstorms in Xiji County, Ningxia. [Method] The drought level was divided by precipitation anomaly percentage and statistically analyzed. The seasonal index and linear trend were used to reflect the trend of drought change in 5 years. The cyclic fluctuation of time series was simulated by polynomials and the decadal scale was changed. The positive part of polynomial decomposition Use bar chart to simulate interannual scale change. [Result] The index of drought season varied greatly and fluctuated from November to June. The general trend of annual drought increased. The decadal-scale drought was most serious before and after 1977, with a period of about 15 years and 20 years. On the interannual scale The drought has risen sharply in recent years; the general trends of drought in March-May and September-November, the decadal and interdecadal changes are discussed and discussed. From the 500hPa weather map, we conducted the classification and classification of the first rainstorm and the rainy weather in Xiji. [Conclusion] These works have important reference value for carrying out drought disaster prevention and mitigation.