青藏高原多雪年与少雪年土壤水热特征模拟分析

Simulation Analysis of Soil Water and Heat Characteristics in High and Low Snowfall Years on the Qinghai-Xizang Plateau

利用耦合了陆面过程模式(CLM4.5)的区域气候模式(RegCM4)分别对青藏高原的一个多雪年和少雪年进行了数值模拟。通过对比模拟雪深与遥感雪深、土壤温湿度的模拟值与观测值、多雪年与少雪年的土壤温湿度模拟值,结果表明,RegCM4-CLM4.5可以有效模拟出高原的多雪年与少雪年特征,模拟雪深大值中心比遥感雪深高10~20 cm。土壤温度模拟效果要明显优于土壤湿度,模拟的土壤温度相关系数R为0.95~0.98,模拟的土壤湿度相关系数R为0.68~0.89。在冻结阶段(10月至次年1月),积雪的异常偏多,可以有效抑制地气间的热交换,从而使得多雪年土壤温度高于少雪年。在季节性冻土区的消融阶段(2-4月和6月),积雪对土壤还具有增湿作用,多雪年土壤湿度高于少雪年。土壤的冻结也会阻碍积雪融水的下渗,因此多雪年与少雪年土壤湿度的差异不超过±2%。在多年冻土区,积雪偏多,冻结深度加大,有利于冻土发育;而在季节性冻土区,积雪增加则不利于冻土发育。

Snow cover and frozen soil on the Qinghai-Xizang Plateau(QXP)play an important role in the global water cycle.In this paper,the Regional Climate Model(RegCM4)coupled with the Community Land Model(CLM4.5)was utilized to conduct regional simulation experiments on the QXP.This was done to explore the mechanism of snow influence on soil water and heat transfer during freezing-thawing periods.Our results showed that RegCM4-CLM4.5 can effectively simulate the characteristics of high and low snowfall years on the QXP,and the center of simulated snow depth was 10~20 cm higher than remote sensing snow depth.The simulation effect of soil temperature was better than that of soil moisture.The correlation coefficient R of simulated soil temperature was 0.95~0.98,and the correlation coefficient R of simulated soil moisture was 0.68~0.89.Comparison of the simulated soil temperature and moisture content of high and low snowfall years on the QXP revealed that the abnormal amount of snowfall had heat preservation and humidification effect on soil.During freezing period,the soil temperature in high snowfall year is higher than that in low snowfall year.During melting period,the soil moisture content in high snowfall year is higher than that in low snowfall year.The frozen soil would also hinder the infiltration of snow melt water,so the difference of soil moisture between the high and low snowfall years was not more than ±2%.In permafrost area,when there was more snowfall,the freezing depth increased,which was conducive to the development of frozen soil.And in seasonal permafrost area,the increase of snowfall was not conducive to the development of frozen soil.