植被变化对西北地区陆气耦合强度的影响  

Research on the impact of vegetation change on land-atmosphere coupling strength in northwest China

作　　者：赵靖川[1] 刘树华[1] 

机构地区：[1]北京大学物理学院大气与海洋科学系,北京100871

出　　处：《地球物理学报》2015年第1期47-62,共16页Chinese Journal of Geophysics

基　　金：国家科技支撑项目(2012BAH29B03);国家重点基础研究发展计划项目(2009CB421402)资助

摘　　要：西北地区地处欧亚大陆腹地,生态系统对于气候变化和人为影响十分敏感,同时该区也是湿润的东亚季风区与干燥的中亚干旱区的过渡区域,陆气相互作用比较强烈.本文对西北地区植被变化对当地的陆气耦合强度及其与之相关的地表水文过程的影响进行了分析研究,并且找出适于增加植被以缓解西北地区荒漠化趋势的最具成效的地区.本文利用美国国家大气科学研究中心（NCAR,National Center for Atmospheric Research）研制的通用大气模式CAM3（Community Atmosphere Model Version 3）对西北地区植被变化的影响进了数值模拟.本文共设计了三个试验,使用正常地表植被覆盖的参考试验,地表下垫面变为裸土的去植被试验和植被增加的生态环境好转试验.首先,本文对西北地区植被变化对于当地降水量、地表水分盈余量、径流量、地表土壤含水量等地表水文变量的影响进行了分析研究.然后对西北地区植被变化对当地的陆气耦合强度的影响进了分析研究,陆气耦合强度是衡量局地陆气相互作用强弱程度的一个新标准,基于计算年降水量与蒸散量的协方差与降水量方差之比而得到.它利用观测数据或模式输出数据,计算起来简便容易,物理意义明确清晰,陆气相互作用越强烈的地区,其陆气耦合强度也越高.最后,本文计算了一个蒸散-水汽通量散度指数来衡量植被变化对局地蒸散与大气水汽通量散度的影响,其在一定程度上反应了植被变化对局地陆气相互作用和大尺度大气环流输送作用的影响,也可以视为一个评估人为生态环境工程效果的指标.西北地区陆气耦合强度由东南向西北递增.去植被之后,西北地区降水与蒸发普遍减少,其中在东南部区域,地表径流增加约10-40mm,渗流量与地表土壤含水量分别减少约40-80mm和5-20mm3·mm-3,陆气耦合强度上升,这有可能导致水土流失,不利于当地植被的�Northwest China is located in the inner center of the Eurasia continent,its ecosystem issensitive to climate variability and anthropogenic alterations.It is the transition zone of the humid East Asia monsoon region and the arid central Asia area,the land-atmosphere interactions are strong there.In this research,the effects of vegetation change on land-atmosphere coupling strength and related land surface hydrological processes in northwest China were examined,and we also tried to confirm the most efficient areas of vegetation increasing for desertification mitigation in northwest China.Using a state-of-the-art Community Atmosphere Model（CAM3）developed by National Center for Atmospheric Research,the effects of vegetation change in northwest China were studied by three numerical experiments：with realistic vegetation characteristics varying monthly（CTL run）,without vegetation（NOVEG run）,and with increased vegetation（VEG run）.Firstly,the influences of vegetation change in northwest China on local hydrological variables（precipitation,surface water surplus,surface runoff,surface soil moisture and so on）were examined.Then,the effects of vegetation change on local land-atmosphere coupling strength were analyzed,land-atmosphere coupling strength is new standard to evaluate the degree of local land-atmosphere interaction,it is based on the ratio of the covariance between annualy precipitation and evaporation anomalies（from their climatological means）over the variance of precipitation anomalies.The coupling strength is easy to compute from observations and standard model output and has a relatively clear physical meaning,and the stronger the local landatmosphere interaction is,the higher the land-atmosphere coupling strength will be.At last,an Evapotranspiration-Moisture flux divergence Index was calculated to evaluate the influences of vegetation change on evapotranspiration and moisture transport in the atmosphere.This index could reflect the effects of vegetation change on local land-atmosphere

关 键 词：西北地区 植被变化 陆气耦合强度 水文变量 数值模拟 

分 类 号：P421[天文地球—大气科学及气象学]