宁夏西吉干旱变化规律及旱情缓解天气形势分析

[目的]分析研究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500 hPa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。

Analysis of Drought Changes and Drought Mitigation in Xiji County of Ningxia

[Objective] The aim was to study the characteristics of the changes of extreme weather climate incidents such as severe drought in northwest and rainstorm in Xiji County of Ningxia. [Method] Precipitation anomaly percentage was applied to divide drought level and for statistics analysis. Seasonal index, linear tendency, and 5-years gliding average were used to reflect the trend of drought changes. The circulation wave of temporal sequence used polynomial expression to simulate the interannual variation scale. The positive part of the polynomial expression used bar chart to simulate interannual variation scale. [Result] The index of drought season from November to June was large. The general trend of annual drought was increasing. The drought of interannual scale was most serious around 1977, about 15 and 20 years. The drought in recent years went up. The general situation of drought, interannual scale and changes of interannual scales from March to May and from September to October were discussed. Based on the weather at 500 hPa, the first rain in Xiji and the drought-turning-into-rain situation were classified. [Conclusion]These may provide reference value to the prevention and mitigation of drought.

1961—2010年中国旱灾时空分布特征研究

采用《中国统计年鉴》和中国农业灾情数据库中的统计资料，重建了1961—2010年中国旱灾的时空分布特征．通过对旱灾时间分布特征的研究结果表明，近50年我国的干旱化程度呈上升趋势．干旱的时间分布存在几个明显的高值区和低值区，旱灾严重年份大多分布在高值区内，旱灾较轻年份大多分布在低值区内．对旱灾空间分布特征的研究结果表明，中国旱灾的空间格局存在东西分异，且以东部型为主．旱灾在不同省（市、区）的分布有很大的差异，山西、河北、内蒙古、山东等省份的旱情比较严重．另外，中国各区域旱灾的季节分布差异也很大，东北、华北和西北地区多发生春、夏旱，长江中下游地区多发生夏、秋旱，华南和西南地区多发生冬春连旱，青藏高原地区的干旱主要发生在5—7月和10月．