气候变暖背景下西太平洋副热带高压体形态变异及热力原因

Morphological variation of the western Pacific subtropical high and its possible thermodynamic causes under the background of climate warming

采用美国NCEP/NCAR再分析资料,利用相关、合成分析、大气热源的计算等方法,研究了气候变暖背景下西太平洋副热带高压(副高)空间形态的变异及热力原因。结果表明,气候变暖前、后各层副高形态特征有很大的差异,副高体的空间形态从850—700 hPa开始显著西伸南扩,到500 hPa最为明显。各层副高在冷、暖期的形态差异与其周围大气热源和涡度的变化相对应。随着气候变暖,副高西侧和南侧的大气热源在850—700 hPa上开始有明显的加强,500 hPa热源加强最明显,且副高体南侧热源中心有所南移;同时,其西侧和南侧从对流层低层至中高层有反气旋涡度的增大,西侧的反气旋涡度在850—700 hPa增大最明显,南侧的反气旋涡度在500 hPa增大最明显,且反气旋中心整体南移。表明气候变暖后,副高体西侧和南侧大气热源的加强,导致相应区域反气旋涡度增大,副高体向反气旋涡度增大的方向发展,从而使副高西脊点西伸,南边界南扩,整体南移。

Based on the NCEP/NCAR reanalysis data, the variation of spatial pattern of the western Pacific subtropical high(WPSH) and the thermodynamic mechanisms leading to the variation, under the background of global warming, are investigated through correlation and composite analysis and calculation of the atmospheric heat sources. It shows that the pattern of the WPSH on all levels varies significantly following the global warming. The scope of the WPSH is found to expand westward and southward above 850-700 hPa, particularly at 500 hPa. The patterns of the WPSH are consistent with the distributions of surrounding heat sources and voticitity both in the cold and warm epochs. Along with the global warming, the heat sources strengthen on the western and southern sides of the WPSH above 850-700 hPa, particularly at 500 hPa, while the heat sources at the southern side move southward. Meanwhile, the anticyclonic vorticity tends to increase on the western and southern sides of the WPSH through the troposphere. Specifically, the most obvious increasing tendency is concentrated in the layer between 850 hPa and 700 hPa on the western side and at 500 hPa on the southern side, while the heat sources as a whole move southward. In summary, the anticyclonic vorticity increases as the heat sources strengthen along with the global warming at the western and southern sides of the WPSH. Consequently, the WPSH expands westward and southward and moves southward as a whole, since it tends to expand following the increasing anticyclonic vorticity.