Temperature and Moisture Advection in the Lower Troposphere Driving the Arctic Surface Radiative Flux Anomalies Associated with the Arctic Oscillation and Arctic Dipole

Atmospheric variability and variability in the Arctic surface energy budget are linked in part through surface longwave and shortwave radiative flux anomalies, generated by changes in the thermodynamic and cloud characteristics within the atmospheric column. Previous studies have shown that this link plays a crucial role in the initialization and acceleration of Arctic sea ice melt. In the results presented, we quantify Arctic-average and regional clear sky and cloud radiative surface flux anomalies associated with the Arctic Oscillation (AO) and Arctic Dipole (AD), two prominent modes of atmospheric variability. This is accomplished through regressions of monthly AO and AD indices with monthly CERES-EBAF surface flux data. Both the AO and AD are associated with significant Arctic-mean clear-sky surface downwelling longwave radiative flux anomalies in late fall and winter. The AD is also associated with an increasing Arctic-mean longwave cloud radiative effect in winter.

Additionally we investigate the changes in the atmospheric column that bring about the associated surface flux anomalies. We determine that the longwave clear-sky flux anomalies associated with AO and AD are a result of changes in temperature and water vapor content in the lower troposphere collocated with the surface flux anomalies. Increased cloud liquid water path in the atmospheric column plays a crucial role in generating the increased longwave cloud radiative effect in winter associated with the AD. Lower-tropospheric temperature and moisture advection from lower latitudes helps generate the key temperature and water vapor anomalies, critically supported by the interaction between the AO- and AD-generated wind and temperature anomaly fields and the mean state.