Modulation of Dynamic Heating in the Winter Extratropics Associated with the Cross-Equatorial Hadley Circulation

Abstract

Abstract The hypothesis that the cross-equatorial Hadley circulation can modulate the poleward heat transport in the winter extratropics is investigated using the Goddard Earth Observing System (GEOS-1) GCM for 10 northern winter initial conditions. Three-month forecasts are compared with parallel runs from the same initial conditions but with a slightly perturbed radiative forcing in the Tropics. Analysis of the zonal-mean climates shows that, on timescales longer than a month, a persistent intensification in the winter Hadley circulation is positively correlated with increased dynamic cooling in the winter midlatitudes and warming at the high latitudes through-out the troposphere, signaling an increased beat transport toward the winter pole. While the heating anomaly can undergo significant transient fluctuations in the winter extratropics, the variance of the time-averaged dynamic heating anomaly is dominated by contributions from low zonal wavenumbers (particularly wavenumbers 1 and 2), with minor con...