Egger, J., and K. Weickmann, 2007: Latitude–Height Structure of the Atmospheric Angular Momentum Cycle Associated with the Madden–Julian Oscillation. Mo. Wea. Rev., 135, 4, 1564-1575.
Abstract
The angular momentum cycle of the Madden–Julian oscillation is analyzed by regressing the zonally averaged axial angular momentum (AAM) budget including fluxes and torques against the first two principal components P1 and P2 of the empirical orthogonal functions (EOFs) of outgoing longwave radiation (OLR). The maximum of P1 coincides with an OLR minimum near 150¡E and a shift from anomalously negative AAM to positive AAM in the equatorial troposphere. AAM anomalies of one sign develop first in the upper-equatorial troposphere and then move downward and poleward to the surface of the subtropics within two weeks. During the same time the opposite sign AAM anomaly develops in the upper-equatorial troposphere. The tropical troposphere is warming when P1 approaches its maximum while the stratosphere is cooling. The torques are largest in the subtropics and are linked with the downward and poleward movement of AAM anomalies. The evolution is conveniently summarized using a time–height depiction of the global mean AAM and vertical flux anomaly.