Subseasonal variability and the "Arctic warming-Eurasia cooling" trend

Area of Science:

• * Climate Science
• * Atmospheric Science
• * Earth System Science

Background:

• * The "Arctic warming-Eurasia cooling" trend significantly influences weather patterns and climate extremes at lower latitudes.
• * This trend has weakened between 2012 and 2021, with increased subseasonal variability in the warm Arctic-cold Eurasia (WACE) and cold Arctic-warm Eurasia (CAWE) patterns.
• * Subseasonal intensity of WACE/CAWE patterns remained comparable to earlier periods (1996–2011) despite the overall trend weakening.

Purpose of the Study:

• * To investigate the co-occurrence of subseasonal variability and trend changes in the WACE/CAWE pattern.
• * To identify the drivers influencing the WACE/CAWE pattern and its subseasonal phase reversals.
• * To understand the implications for predicting climate extremes at mid- to low latitudes.

Main Methods:

• * Analysis of long-term reanalysis datasets.
• * Utilization of Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations.
• * Numerical experiments using the Community Atmosphere Model (CAM) and Atmospheric Model Intercomparison Project (AMIP).

Main Results:

• * Tropical Atlantic and Indian Ocean sea surface temperature anomalies significantly impact the WACE/CAWE pattern in early and late winter, respectively.
• * These ocean temperature anomalies were confirmed as primary drivers through numerical experiments.
• * The coordination of tropical ocean influences effectively modulates subseasonal phase reversals between WACE and CAWE patterns, as observed in winters 2020 and 2021.

Conclusions:

• * Subseasonal variability plays a crucial role in modulating the WACE/CAWE pattern, even as the long-term trend weakens.
• * Tropical ocean conditions are key predictors for the subseasonal phase of the WACE/CAWE pattern.
• * Subseasonal climate dynamics must be considered for accurate prediction of climate extremes in mid- to low latitudes.