北方农牧交错带降水极值变化空间特征

农牧交错带是我国生态环境脆弱带,以109个气象站1971～1998年间的逐日降水资料,分析了农牧交错带年降水量、侵蚀性降水及暴雨等方面降水极值的时间变化及空间分布。结果显示农牧交错带平均每年发生侵蚀性降水的日数在3.5～17.6d之间,暴雨日数在0～2.6d之间;大部分地区的年降水量、侵蚀性降水量及暴雨量等都呈现不同程度的增加趋势,但暴雨量以及侵蚀性降水量等降水极值指标增加趋势更明显,反映出多数地区降水强度增加、降水侵蚀的潜在能力增强的特征;局部地区的降水极值呈减少趋势。

Spatial distribution of precipitation extremum in the ecotone between agriculture and animal husbandry in northern China

The ecotone between agriculture and animal husbandry in northern China is the fra-gile zone of ecological environment.Changes of rainfall extreme s will have tremendous influ ence on agriculture and animal husbandry.Daily rainfall amount of109weather stations from1971to1998is used to analyze the annual change and spatial distribution of rainfall extremes in the e-cotone between agriculture and animal husbandry in northern China.The rainfall extremes com-prise five parameters of annual rainfall,annual erosive rainfall,annual erosive rainfall days,an-nual rainstorm,and annual rainstorm days.The result shows that annual average erosive rainfall is between3.5and17.6days and rainstorm is between0and2.6days.Annual rainfall,erosive rainfall and rainstorm have increased gradually in recent 30years in most parts of the ecotone between agriculture and animal husbandry in northern China,and the annual rainstorm and ero-sive rainfall have increased more quickly than annual rainfall which shows that the rainfall in-tensity has increased and the potential erosion capability of rainfall has enhanced in most parts.The areas of positive change trend center in Chifeng and Tongliao of Inner Mongolia,Wuzhai in Shanxi province,and Yanchi in Ningxia Hui Autonomous Region.The rainfall extremums have deceased in only some areas and the areas of negative change trend center in Xixian county of Shanxi province and Luochuan in Shaanxi province.