Impacts of Stratospheric Polar Vortex Shift on the East Asian Trough

Abstract

Impacts of stratospheric polar vortex shift on the wintertime East Asian trough (EAT) on intraseasonal time scales are investigated using a reanalysis dataset and a climate model. The result based on composite analysis shows that the shift of the stratospheric polar vortex toward eastern Siberia (ES-shift event) is associated with higher geopotential height at 500 hPa than normal over East Asia, corresponding to the weakened EAT. Furthermore, the simulated EAT is also weakened when nudging the stratospheric state toward that during the ES-shift events. This study further found that there is no significant difference in the stratospheric polar vortex intensity between the ES-shift events and nonshift events, implying that the polar vortex strength change may have little influence on the possible connection between the polar vortex shift and the EAT change. The underlying mechanisms are listed as follows: First, the positive potential vorticity (PV) anomalies in the lower stratosphere associated with ES-shift events could explain approximately 40% of the local westerly anomalies in the upper troposphere to the north of East Asia via PV conservation, leading to the rise of the geopotential height over East Asia and the weakening of the EAT. Second, the shift of stratospheric polar vortex could modulate the synoptic-scale Rossby wave activity in the upper troposphere, favorable for the southward propagation of synoptic-scale waves and divergence of extended Eliassen-Palm flux in the upper troposphere. Finally, the transient wave feedback could enhance the tropospheric westerly anomalies in the north of East Asia and induce positive height anomalies to its south, further weakening the EAT. Our results revealed that the stratospheric polar vortex shift leads the EAT intensity variation by around 2–5 days, implying that the stratospheric polar vortex shift could be applicable to the prediction of the EAT intensity.

Observations of Inertia Gravity Waves in the Western Pacific and Their Characteristic in the 2015/2016 Quasi‐Biennial Oscillation Disruption

“…The enhanced westward forcing exerted by IGWs in the westerly phase disruption is also confirmed by MERRA-2 data (Kang et al, 2020), and our results further investigate the observed GW during 2015/16D in detail. This study presents the activity characteristics of IGWs in the western Pacific during 15/16D from the perspective of observation for the first time, which can be used to supplement and confirm the discussion on the role of multi-scale wave activity to the mean flow by various models and reanalysis data (Chang et al, 2022;Coy et al, 2017;Garcia & Richter, 2019;Holt et al, 2016;Kawatani et al, 2009;Kim & Achatz, 2021;Li et al, 2020;Newman et al, 2016;Zhang et al, 2022).…”

Analysis of Atmospheric Elements in Near Space Based on Meteorological-Rocket Soundings over the East China Sea

“…Currently, the dynamic processes in near space have become a research hotspot in the context of climate change, as they can provide an important basis for ensuring the normal operation of spacecraft and improving the accuracy of numerical weather prediction [18,19]. Gravity waves, Kelvin-Helmholtz instability (KHI), and turbulence, as important physical processes in near space, have been extensively studied through various types of detection equipment and numerical simulations [20][21][22][23].…”