渤、黄海冬、夏季节风生流场年际变化时空模态与环流变异

Spatiao-temporal modes and circulation variation on the interannual variation of seasonal mean wind-driven current field in the Bohai Sea and Yellow Sea in winter and summer

根据1975—2017年冬、夏季节渤、黄海沿岸25个气象站风观测资料,采用二维非线性垂直平均风生流模式、旋转经验正交函数(REOF)等方法,研究了渤、黄海冬、夏季节平均风生流速度势与流函数场年际变化时空模态与环流变异.由于冬、夏季节渤、黄海风应力场强度年际变化显著线性减弱趋势,冬季渤、黄海平均速度势与流函数强度年际变化线性减弱速率大于夏季,黄海冬、夏季平均速度势与流函数强度年际变化线性减弱速率大于渤海.渤、黄海冬、夏季节平均风生流速度势与流函数场年际变化主要有两种时空模态,冬季渤海垂直环流显著线性减弱以及水平环流准平衡态年际变化是主要分量,冬季黄海垂直与水平环流准平衡态年际变化是主要分量.夏季渤海垂直环流显著线性减弱以及水平环流准平衡态年际变化是主要分量,夏季黄海大部分海域垂直环流显著线性减弱与局部垂直环流显著线性增强年际变化是主要分量,夏季黄海水平环流形态此消彼长显著线性增强及减弱年际变化是主要分量.冬季黄海暖流暖水向南黄海西侧以及向渤海中部输送过程是在3～4个环流之间传递形成,并非由单一环流输送形成.冬季渤海中部辐散下沉反气旋环流与黄海中部至渤海海峡的气旋环流、黄海东部辐散下沉反气旋环流是冬季黄海暖流强度与范围的控制环流,夏季渤海中部辐散下沉反气旋环流与黄海中部辐合上升气旋型环流是夏季渤、黄海冷水团强度与范围的控制环流,冬、夏季节渤、黄海控制环流年际变化形态的变换形成冬季黄海暖流与夏季渤、黄海冷水团暖年或冷年的年际变化.

Based on the wind data obtained from 25 meteorological observation stations along the coast of the Bohai Sea and Yellow Sea in winter and summer from 1975 to 2017,the spatiao-temporal modes and circulation variation on the interannual variation of seasonal mean wind-driven current velocity potential and stream function field in the Bohai Sea and Yellow Sea in winter and summer were studied with methods of the two dimensional nonlinear vertical mean wind-driven current model and Rotated Empirical Orthogonal Function (REOF).Since interannual variation of wind stress field intensity significantly decreased linearly in winter and summer,the interannual variation linear decreasing rate of mean velocity potential and stream function intensity is greater in winter than that in summer.The interannual variation linear decreasing rate of mean velocity potential and stream function intensity in the Yellow Sea in winter and summer are greater than that of the Bohai Sea.The interannual variation of seasonal mean wind-driven current velocity potential and stream function field has two spatiao-temporal modes.The vertical circulation was significantly weakened linearly and the interannual variation of the quasi equilibrium state of the horizontal circulation is the major component in the Bohai Sea in winter.The interannual variation of the quasi equilibrium state of the vertical and horizontal circulations is the major component in the Yellows Sea in the same season.In summer,the vertical circulation in the Bohai Sea is significantly weakened linearly and the interannual variation of the quasi equilibrium state of the horizontal circulation is the major component in the Yellow Sea in summer when the vertical circulation in most of areas is significantly weakened and the interannual variation of the significant linear enhancement of the local vertical circulation is the major component.In winter the transmutation of the Yellow Sea Warm Current to the west and to the center Bohai Sea is finished by 3 to 4 circulations rather than a single circulation.In winter,the anticyclone circulation with divergent subsidence occurs in the center Bohai Sea and the eastern Yellow Sea,and the cyclonic circulation in the central Yellow Sea and the Bohai Strait are the control circulation for the intensity and range of the Yellow Sea Warm Current in winter.In summer,the anticyclonic circulation with divergent subsidence in the center Bohai Sea and the cyclonic circulation with convergence and the upwelling in the center Yellow Sea are the controlled circulation of the intensity and range of the cold water masses of the Bohai Sea and Yellow Sea.In winter and summer the interannual variation of controlled circulation state changes and it follows the warm/cold year interannual variations of the Yellow Sea Warm Current and cold water mass in the Bohai Sea and Yellow Sea.