Responses of the Stratospheric Arctic Vortex to Regional Sea Surface Temperature Changes

The stratospheric Arctic vortex (SAV) plays a critical role in forecasting cold winters in the northern mid-latitudes. In this study, we systematically examined the responses of SAV intensity to regional sea surface temperature (SST) changes using idealized SST patch experiments with a climate model. Our findings reveal that the SAV intensity is most sensitive to SST variations in the tropics and northern midlatitudes during boreal winter (December–January–February; DJF). Specifically, warming in the tropical Pacific and Atlantic leads to a weakening of the SAV, while warming in the tropical Indian Ocean, northern mid-latitude Atlantic, and northwestern Pacific strengthens the SAV. Notably, the most substantial SAV weakening (strengthening) is triggered by warming in the tropical western Pacific (tropical central Indian Ocean), with a maximum magnitude of approximately 2.23 K/K (-1.77 K/K). The SST warming in the tropics influences the tropical convections, which excite Rossby wave trains. These wave trains can interfere with the climatological waves in the mid–high latitudes, while the SST warming in the northern midlatitudes can influence tropospheric planetary wavenumber-1 and wavenumber-2 directly. The changes in tropospheric planetary waves modulate the upward propagation of wave activities and impact the SAV intensity. Additionally, the response of the SAV to tropical SST changes especially over the Indian Ocean and subtropics exhibits significant nonlinearity.