西北地区东部季节干旱的时空变化特征分析

干旱作为我国西北地区东部影响最大的气象灾害, 可引起农业减产、水资源短缺、土地荒漠化和生态环境恶化等严重问题.在国家新一轮西部大开发战略实施之初, 在全球气候变暖背景下, 有必要对干旱发展的最新特征和演变趋势进行详细分析研究, 为加强防旱、抗旱,促进经济发展提供科学决策依据和参考.采用国家干旱标准综合干旱指数(CI指数), 利用西北地区东部74个气象代表站逐日气温、降水资料, 分析了西北地区东部不同级别干旱日数在各个季节的时空分布和变化趋势. 结果表明: 在气候变暖背景下, 西北地区东部从长期趋势看, 春、夏、秋季干旱呈加剧趋势, 冬季干旱呈减轻趋势. 21世纪以来春、夏季干旱进一步加剧, 尤其是夏季加剧更显著, 而秋、冬季干旱出现了减弱的新趋势. 在西北地区东部主降水期3-11月重-特旱加剧趋势比轻-中旱加剧显著, 南部干旱化趋势比北部更加明显. 尤其是宁夏同心地区春旱加剧非常显著, 已成为西北地区东部重-特旱最严重的地区.对于干旱发展的这一新动态, 必须引起有关部门的高度重视, 采取科学、有效手段加强防旱、抗旱.

An Analysis of the Characteristics of Temporal and Spatial Variation of Seasonal Drought in the East of Northwest China

Drought, the most serious meteorological disaster, can induce serious problems such as agricultural production reduction, water shortage, land desertification, ecological environment degradation and so on. At the beginning of a new round of the national implementation of the western development strategy, under the background of global warming, it is necessary to analyze the new characteristics and variation trend of drought in detail for providing scientific decision-making and reference of strengthening prevention and fight against drought, in order to further promote economic development. Based on the daily air temperature and precipitation data from 74 meteorological observation stations in the east of Northwest China, adopting the national standard comprehensive drought index (CI index), application of which has been promoted to all over the country in recent years, the temporal and spatial distribution and variation trend of different levels of drought days in different seasons in the east of Northwest China are analyzed in detail. It is found that under the background of global warming, the long-term trend of drought is aggravating in spring, summer and autumn, but is lightening in winter in the east of Northwest China. Since the beginning of the 21st century, the spring and summer droughts have aggravated, especially in summer, while the autumn and winter droughts have lightened. The severe/extreme severe drought from March to November has intensified more significantly than light/medium drought, and the drought trend in south part has intensified more than that in the north part. Furthermore, it is found that the spring drought has aggravated significantly in Tongxin of Ningxia, where a most serious area of severe/extreme severe drought in the east of Northwest China is forming. To this new trend of drought development, it is necessary to pay great attention for the related departments, and to adopt scientific and effective methods to strengthen preventing and fighting against the drought.