利用NCEP/NCAR和OAFlux月平均资料,采用SVD方法分析冬季黑潮海域的热通量和北太平洋500hPa位势高度场之间的关系。第1对奇异向量占总方差的86.24%,表现为黑潮北部海域异常多的放热和北太平洋中西部的500hPa位势高度场异常低。将正负异常年的各气象要素的距平场进行合成分析后表明:当阿留申低压增强(减弱)时,黑潮海域上空的西北风增强(减弱),导致近地面层大气温度降低(升高),使得热通量异常释放增加(减少),从而降低(升高)了海表面温度。在黑潮海域及其下游,温度场在纬向垂直方向是斜压结构,位势高度场是相当正压结构,反映的是冷低压(暖脊)结构。通过分析风场无旋分量和垂直速度的距平发现,在中纬度地区存在距平的纬向环流圈:大气在北太平洋中部的低层上升(下沉),在对流层高层(低层)分别向西、向东运动,在黑潮海域和北美西部下沉(上升),增强(减弱)了中纬度纬向环流圈(MZC)。
The Singular Vector Decomposition(SVD) analysis of monthly data of the NCEP-NCAR reanalysis and OAFlux reanalysis data for wintertime is used to study the relationship between the Kuroshio anomalous heating and the North Pacific geopotential height at 500 hPa. The first SVD mode shows that the anomalous heating in northern Kuroshio is associated with anomalously low geopotential height in the central and western parts of the North Pacific at 500 hPa. Composite analysis of meteorological variables for both positively and negatively anomalous years reveals that while the Aleutian low strengthens(weakens), the north-westerly wind overlying the Kuroshio strengthens(weakens) and induces the cooling(warming) of the air near the sea surface, and further increases(decreases) the upward anomalous heat flux and cools(warms) the sea surface temperature. Over the Kuroshio and its downstream region, the vertical structure of air temperature along the latitude is baroclinic while the geopotential height is equivalently barotropic. This reflects a cool-low(warm-ridge) spatial structure. Analysis of divergent wind and vertical velocity shows the existence of an anomalously zonal circulation cell. It is characterized by air rising (falling) in the central North Pacific, flowing westward and eastward in the upper troposphere, and falling (rising) in the Kuroshio region and the west of the North America, which strengthens(weakens) the mid-latitude zonal cell(MZC).