Enhanced stratosphere-troposphere and tropics-Arctic couplings in the 2023/24 winter

Abstract

The stratosphere-troposphere and the tropics-Arctic couplings were intermittently enhanced in the 2023/24 winter. Here we used ERA5 reanalysis data and found that due to the amplification of planetary wavenumber 1 and 2 pulses, three displacement-type sudden stratospheric warming events occurred in one winter under the background conditions of warming equatorial middle and east Pacific, active equatorial convections, and easterly stratospheric equatorial winds. During the sudden stratospheric warming events, the stratospheric disturbances propagated downward to the surface, followed by continental cold surges. The residual meridional circulation was strengthened across the tropics and Arctic, anomalously more water vapor was transported into the stratosphere in tropics, while ozone content diminished in the lower stratosphere and grew in the upper stratosphere over the tropics. Meanwhile, water vapor and ozone over the Arctic exhibited a dipping pattern from the upper to the lower stratosphere. In early 2024, three sudden stratospheric warming events occurred due to warming equatorial middle and east Pacific, active equatorial convections, and easterly equatorial winds, enhancing stratosphere- troposphere and tropics-Arctic coupling, according to analysis of zonal wind, temperature, and geopotential height from ERA5 reanalysis data.