近30年来中国陆地蒸散量和土壤水分变化特征分析

 对NOAH陆面模式模拟的近30年中国陆地蒸散量和土壤含水量,按照6大片区和5种生态系统类型进行了统计分析。讨论全国以及各大区不同生态系统类型蒸散和土壤含水量的变化,研究不同类型蒸散和土壤含水量的关系。中国陆地蒸散量总体呈增加的趋势,年内蒸散量最大的月份是7月,年末和年初蒸散量较小。而我国中南、西南、华东、东北和西北蒸散量变化趋势和全国的总趋势一致,呈增加的趋势。华北地区蒸散量近30年来总体趋势是下降的,华北蒸散量最大的年份是上世纪90年代。在所有生态系统类型中,林地蒸散最大的有东北、华东、西南和中南4区;而华北和西北草地在各类型中蒸散量所占比例最高。6大片区对比,林地蒸散水量最大的地区是西南和中南,最小的西北;草地蒸散水量最大的地区是西南,最小的是东北区;农田蒸散水量最高的是华东,最低的是西北;荒漠蒸散量最大的片区是西北;湿地蒸散最大的是东北。80年代以来,全国土壤含水量总体呈下降的趋势。从各片区的情况看,仅西北地区稍有增加,其余5区土壤含水量皆是下降的。植被覆盖度和土壤水分是影响蒸散量最重要的因子,在植被覆盖较差时,土壤水分和蒸散量相关性较好。

Changing Characteristic of Land Surface Evapotranspiration and Soil Moisture in China during the Past 30 Years

The land surface evapotranspiration（ET） and soil moisture used in this paper were retrieved from land surface model（LSM） of NOAH.The variation of land surface ET and soil moisture was analyzed by statistics in six large regions and by four ecosystem types in China.Then the relationship between ET and soil moisture was discussed.The long term trend of land surface ET was increasing in China.The maximum ET occurred in July,while the minimum one was usually at the beginning/end of a year.The trend of ET in South-Central China,Southwest China,East China,Northeast China and Northwestern China was also increasing,agreed with the whole China.The long term variation trend of ET was decreasing in North China,where the maximum ET was 43.091 Billion Cubic Meters（BCM） in 1990.The relative ratio of evapotranspiration of forest was the highest among all the ecosystem types in Northeast,East,Southwest and South-Central China,while the highest one was grassland in North and Northwest China.To compare the amount of water used by evapotranspiration,the biggest forest ET was in Southwest and South Central China,the smallest was in Northwest China;the biggest grassland ET was in Southwest China,the smallest was in Northeast China;the biggest farmland ET was in East China,the smallest was in Northwest China;the biggest ET for desert and wet land was in Northwest and Northeast China respectively.The soil moisture was decreasing in most China regions except for that in Northwest China ever since 1980s,agreed with the whole China.The main impact factors of ET were vegetation fraction and soil moisture.There existed a good relationship between soil water content and evapotranspiration in rare vegetation covered regions.