北极涛动驱动的冬春欧亚陆面变量异常及其机理OACSTPCD

As the leading mode of wintertime atmospheric circulation interannual variability in the mid-to-high latitudes of Northern Hemisphere,the Arctic Oscillation(AO)can serve as a crucial source of climate predictability.However,its effects on land surface variables such as surface temperature,soil moisture and snow cover lack a thorough investigation.The impact of AO on land surface variables in Eurasia and associated mechanisms were examined,via regression analysis and diagnosing physical processes based on the datasets of ERA5 and ERA5-Land reanalysis.The main results are as follows:during a positive phase of AO,anomalous land surface warming(cooling)occurs in northern(southern)Eurasia,characterized by a meridional dipole pattern.Meanwhile,snow cover/depth and soil moisture anomalies feature a meridional tripole pattern,that is,decreased snow cover/depth and soil moisture are observed in the most of mid-latitude regions of Eurasia while increased snow cover/depth and soil moisture occurs in the high-latitude and low-latitude regions.It was further found that anomalous water vapor transports induced by the AO-related atmospheric circulation anomalies dominate the formation of those land surface variable anomalies.Anomalous land surface warming(cooling)in northern(southern)Eurasia mainly are caused by increased(decreased)downward long-wave radiation due to the increase(decrease)of water vapor and clouds which result from anomalous convergence(divergence)of water vapor transport in northern(southern)Eurasia.Meanwhile,anomalous precipitation in the form of snowfall or rainfall resulting from anomalous water vapor transport explains the snow cover/depth and soil moisture anomalies.Decreased(increased)snowfall or rainfall resulting from anomalous divergence(convergence)of water vapor transport cause decreased(increased)snow cover/depth,snowmelt and soil moisture in mid-latitude Eurasia(high and low latitude Eurasia).In addition,AO-driven snow cover anomaly tends to amplify the land surface temperature anomaly in Tibetan Plateau through snow-albedo feedback.