Oral or Poster

IAMAS

M05 - Advances in Dynamic Meteorology

Dynamical characteristics of the summer Arctic Oscillation

The Summer Arctic Oscillation (SAO) has not been studied as extensively as its winter counterpart (WAO), yet recent research indicates that the SAO is linked to extreme heat events across the Northern Hemisphere. This study utilizes reanalysis and satellite data to explore both the spatial characteristics and the underlying dynamics of the SAO. Unlike the WAO, which reflects the north-south shifts of the eddy-driven jet around 40N, the SAO is characterized by zonal wind anomalies occurring in two distinct regions: the subtropics and near the Arctic coast. The subtropical anomalies are primarily influenced by meridional wave propagation, whereas those near the Arctic coast are largely driven by surface-level baroclinic eddy activity. Results highlight the significant role of Arctic cloud cover in modulating the SAO, as it enhances the low-level meridional temperature gradient via the shortwave cloud radiative effect. Furthermore, the SAO index exhibits a strong positive correlation with both Arctic cloud cover and upper-level zonal winds along the Arctic coastline, indicating a distinct double jet structure in the Northern Hemisphere during positive SAO phases. These findings offer fresh insights into the dynamics of annular modes during the Northern Hemisphere summer and underscore the importance of further research into the unique behavior of summer jet streams compared to their winter counterparts.