Low-frequency Variations in the General Circulation and Climate Processes

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This study is aimed at diagnosing processes responsible for low-frequency variations in the general circulation of the atmosphere relevant to climate dynamics. The PIs plan to identify the mechanisms that give rise to changes in atmospheric angular momentum (AAM) on interannual and longer time scales. Newly available data sets will be used to examine the surface torques responsible for ENSO anomalies in AAM and the manner in which the surface sources and sinks of momentum are linked to behavior in the upper troposphere. Stationary wave activity fluxes will be computed to investigate further the way in which low-frequency variations in tropical angular momentum become communicated to the extratropics. Regions responsible for the presence of regimes in the AAM time series and in the Hadley circulation will be determined using the 30-year archive of zonal and meridional winds in the General Circulation Data Library. Finally, the Pi will update and extend their analysis of the impact of doubling CO2 on zonal winds and AAM by considering suitable experiments with current versions of general circulation models. This research is important because it strives to understand how variations in the earth's angular momentum affects atmospheric processes on interannual and interdecadal time scales.