冬季与北大西洋涛动相关Rossby波列传播特征及对下游气候的影响

Propagation Characteristics of Rossby Wave Trains Associated with the North Atlantic Oscillation in Winter and Their Impacts on Downstream Climate

利用再分析数据,以在北半球冬季与北大西洋涛动(North Atlantic Oscillation,NAO)相关的向下游传播的准定常波列在欧洲地区是否发生反射为标准,将1957/1958年至2001/2002年这45个冬季分为高纬型和低纬型两类冬季,分别简称为在H型和L型冬季。在H(L)型冬季,和NAO相联系的向下游传播的Rossby波列主要沿高纬度(低纬度)路径传播。对比了在两种类型冬季NAO与同期大气环流、近地面温度(Surface Air Temperature,SAT)、海表面温度(Sea Surface Tempertaure,SST)和降水的关系。结果表明:大气环流方面,在H型冬季,300 hPa位势高度异常在西-西伯利亚和中-西伯利亚西部与NAO呈现正相关,而在L型冬季300 hPa位势高度异常在亚洲东海岸(约40°N)和北太平洋呈现正相关,在H型冬季与NAO相关的经向风异常在中纬度形成波列,而在L型冬季与NAO相关的经向风异常在副热带形成波列;SAT方面,在H型冬季SAT异常在欧亚大陆腹地高纬度地区与NAO呈现正相关,而在L型冬季与NAO相关的SAT异常在欧亚大陆腹地的高纬度地区相对较弱,但NAO造成的SAT异常可以扩展到亚洲东北部;降水方面,H型冬季与L型冬季主要区别在中国南方,在H型冬季降水异常与NAO的关系相对较弱,而在L型冬季降水异常与NAO呈现正相关关系;SST方面,同期SST异常在北大西洋中纬度海域与NAO呈现正相关,而在L型冬季与NAO相关的SST异常在北大西洋中纬度地区相对较弱,在北大西洋北部和南部较强。总体而言,在H型和L型冬季,NAO具有不同下游影响。

Using reanalysis products, we can divide the 45 winters from 1957/1958 to 2001/2002 into two types, i.e., high latitude (H) and low latitude (L), based on whether the quasi-stationary wave trains propagating downstream in the Northern Hemisphere in the winter are reflected in Europe. The wave reflection is related to the North Atlantic Oscillation (NAO). In the H (L) type winter, the Rossby wave trains associated with the NAO mainly propagate downstream along the high-latitude (low-latitude) path. We compared the relationships between the NAO and atmospheric circulation, surface air temperature (SAT), sea surface temperature (SST), and precipitation in the two types of winter. The results show that in the H-type winter, 300-hPa geopotential height anomalies are positively correlated with the NAO in western Siberia and western-central Siberia, while in L-type winter, 300-hPa geopotential height anomalies are positively correlated with the NAO in eastern coast of Asia (about 40°N) and North Pacific;meridional wind anomalies associated with the NAO in the H-type winter form wave trains in the mid-latitude, while in the L-type winter, meridional wind anomalies form wave trains in the subtropics;SAT anomalies in the H-type winter are positively correlated with the NAO in the high latitudes of inland Eurasia, while SAT anomalies in the L-type winter are relatively weak in the high latitudes of inland Eurasia, but the SAT anomalies caused by the NAO can extend to northeastern Asia. Main differences in precipitation between the H-type winter and L-type winter are found in China. In southern China, the relationship between the H-type winter precipitation anomalies and the NAO is relatively weak, while that between the L-type winter precipitation anomalies and NAO is positively correlated;SST anomalies are positively correlated with the NAO in the mid-latitude area of the North Atlantic during the same period, while the SST anomalies related to the NAO in the L-type winter are relatively weak in the mid-latitude area of the North Atlantic, and stronger in the northern and southern North Atlantic. Generally speaking, the NAO has different downstream effects in the H-type and L-type winters.