全球土壤湿度的记忆性及其气候效应

利用1948-2010年全球GPCC月平均降水,GHCN_CAMS月平均气温资料,GLDAS-NOAH月平均、3 h土壤湿度和降水资料以及观测资料,分析了土壤湿度与降水和气温之间的关系.结果表明:全球土壤湿度记忆性的时间尺度在20~110 d不等,干旱地区浅层(0~10 cm)土壤湿度记忆性较短,中深层(10~200 cm)较长,湿润区及高山地区土壤湿度记忆性均较长,北半球春季土壤湿度记忆性最长,南半球夏季土壤湿度记忆性最长;降水和气温对同期土壤湿度在不同地区的作用不同,北半球夏、秋季降水是土壤湿度的主要来源,除非洲干旱区以外的中低纬度地区及南半球,土壤湿度随降水的增加而增加,随气温的升高而减小;浅层土壤湿度受同期降水和气温的影响最为显著;前期降水和气温对土壤湿度的影响存在着较大的空间差异,北半球中高纬度地区,当年的夏、秋季降水是次年春季土壤湿度的主要来源,中层土壤(10~100 cm)是降水的主要存储层.浅层土壤受外界影响较大,对前期气候信息的存贮有限.中低纬度地区及南半球,中深层土壤更多地是存储前一个季节的气温和降水信息,对跨季节气候信息的存储并不明显;低纬度地区春季土壤湿度的增加可能有利于后期降水的增多,高纬度地区春季土壤湿度的增加可能使后期降水减少,在季节尺度上中层土壤湿度对后期的降水影响较明显,在月至日尺度上浅层土壤湿度对后期降水的影响更重要;春季干旱区尤其是中层土壤湿度的增加可能有利于夏季气温的降低.

The memory and climate effects of global soil moisture

The relationship between soil moisture and precipitation and air temperature was analyzed using the monthly precipitation data of GPCC,temperature data of GHCN_CAMS,monthly mean soil moisture data of GLDAS-NOAH and 3-hourly precipitation and soil moisture of GLDAS-NOAH and observational data for the period from 1948 to 2010.The results show that the temporal scale of global soil moisture memory varies from 20 days to 110 days.In the arid areas,the shallow soil moisture memory (0 ～ 10 cm) is shorter than the middle and deep soil moisture memory (10 ～ 200 cm);the soil moisture memories in humid and high mountain areas are longer than that in arid areas.The soil moisture memory in the Northern Hemisphere is the longest in spring and that in the Southern Hemisphere is the longest in summer.Precipitation and temperature have different effects on soil moisture in different regions within the same period.The summer and autumn precipitations in the Northern Hemisphere are the main sources of soil moisture,and in mid-low latitudes and Southern Hemisphere,except for the African arid regions,soil moisture increases with precipitation and decrease with temperature.The shallow soil moisture is significantly affected by precipitation and temperature in the same period.The effects of precipitation and temperature in the previous period on soil moisture have spatial difference.The summer and autumn precipitations in the mid-high latitudes of the Northern Hemisphere are the main sources of soil moisture in the spring of next year,and the middle layer soil (10 ～ 100 cm) is the main water reservoir layer.The shallow soil is greatly affected by the external environment,of which the ability of saving climatic information is limited.In mid-low latitudes and the Southern Hemisphere,the middle and deep soils mainly save the information of temperature and precipitation in the previous season,with insignificant information of those more than one season.The increase of spring soil moisture in low latitudes may be beneficial to the subsequent precipitation,and the increase of spring soil moisture in the high latitudes may reduce the subsequent precipitation.The effect of the middle soil moisture on the subsequent precipitation is significant in seasonal scale,and the influence of the shallow soil moisture on the subsequent precipitation is more important in daily-to-monthly scale.The increase of spring soil moisture,especially in the middle part,of the arid areas may be beneficial to the decrease of summer temperature.