[A-CG34] Climate Variability and Predictability on Subseasonal to Multidecadal Timescales

[ACG34-05] Different teleconnection patterns and resultant turnabout of anomalous air temperature over East Asia in winter 2020/21

*Masaya Kuramochi¹, Hiroaki Ueda² (1.Graduate School of Science and Technology, University of Tsukuba, 2.Faculty of Life and Environmental Sciences, University of Tsukuba)

Keywords:teleconnection, heat source response, East Asian winter monsoon, climate variability, intraseasonal oscillation

Turnabout of air temperature anomaly over the Far East between first and latter half of winter 2020/21 was examined from a teleconnection perspective with regionally different convective heating anomalies over the Indo-Pacific sector. In the first half, air temperature over the Far East was colder than normal, which was accompanied by a pair of anticyclonic and cyclonic anomalies over the southeast of the Tibetan Plateau and the north of Japan, respectively, in the upper troposphere. This dipole pattern is indicative of propagation of the Rossby wave caused by enhanced tropical convection over the eastern Indian Ocean towards the South China Sea. In the latter half of the winter, the enhanced convection shifted eastward to the Philippine Sea and the subsequent anticyclonic anomaly changed its position to the south of Japan, which resulted in warmer condition over the Far East. It was confirmed from composite analysis based on monthly mean data that an anticyclonic anomaly over the southeast of the Tibetan Plateau is closely related to intensified convection over the South China Sea, while the half cases of an anticyclonic anomaly over the south of Japan is accompanied by anomalous convection over the Philippine Sea. Sensitivity experiments using the linear baroclinic model prescribed diabatic heat source at the South China Sea and at the Philippine Sea reproduce the different anomalous circulation corresponding to the first and the latter half of the winter, respectively. Moreover, the vorticity budget analysis suggests that the presence of upper tropospheric convergence to the southeast of the Tibetan Plateau seen in the climatology is conceivable for the in situ localized anomalous circulation due to the stretching effects.