Atmospheric eddy anomalies associated with the wintertime North Pacific subtropical front strength and their influences on the seasonal-mean atmosphere

作者：Wang, LiYing; Hu, HaiBo^*; Yang, XunQun; Ren, XueJuan

来源：Science China Earth Sciences, 2016, 59(10): 2022-2036.

DOI：10.1007/s11430-016-5331-7

• North Pacific subtropical front
• Frequency
• Eddy activity
• Mid-Latitude
• Ocean-Atmosphere interaction

This study investigates transient eddy activity anomalies in the mid-latitude upper troposphere associated with intensity variability of the wintertime North Pacific subtropical front. Our results show that the meridional gradient of air temperature and baroclinic instability in the mid-latitude atmosphere become stronger as the subtropical front intensifies, and the mid-latitude westerly jet accelerates with barotropic structure. We further divide the mid-latitude atmospheric eddy activities into high- (2-7 days) and low-frequency (10-90 days) eddy activities according to their life periods. We find that, when the oceanic subtropical front intensifies, the high-frequency atmospheric eddy activity in the mid-latitudes strengthens while the low-frequency eddy activity weakens. The stronger high-frequency eddy activity tends to moderate the air temperature gradient and baroclinicity in the mid-latitudes. High-frequency eddy anomalies accelerate the westerly jet on the northern side and downstream of the westerly jet, and enhance the jet with equivalent barotropic structure. In contrast, the weaker low-frequency eddy activity has a negative contribution to zonal wind speed tendency and attenuates the zonal homogenization of the jet. The anomalous thermodynamic forcing of the low-frequency eddy activity helps maintain the meridional gradient of air temperature in the mid-troposphere.

• 出版日期2016-10
• 单位南京大学