Observed Signatures of the Barotropic and Baroclinic Annular Modes in Cloud Vertical Structure and Cloud Radiative Effects

AbstractThe signatures of large-scale annular variability on the vertical structure of clouds and cloud radiative effects are examined in vertically resolved CloudSat and other satellite and reanalysis data products. The northern and southern “barotropic” annular modes (the NAM and SAM) have a complex vertical structure. Both are associated with a meridional dipole in clouds between subpolar and middle latitudes, but the sign of the anomalies changes between upper, middle, and lower tropospheric levels. In contrast, the northern and southern baroclinic annular modes have a much simpler vertical structure. Both are linked to same-signed anomalies in clouds extending throughout the troposphere at middle to high latitudes. The changes in cloud incidence associated with both the barotropic and baroclinic annular modes are consistent with dynamical forcing by the attendant changes in static stability and/or vertical motion. The results also provide the first observational estimates of the vertically resolved a...