Circulation responses to surface heating and implications for polar amplification

Abstract

A seminal study by Hoskins and Karoly (1981) explored the atmospheric circulation response to tropospheric heating perturbations at low latitudes and midlatitudes. Here we revisit and extend their study by investigating the circulation and temperature response to low, middle, and high latitude surface heating using an idealised moist grey radiation model. Our results corroborate previous findings showing that heating perturbations at low latitudes and midlatitudes are balanced by different time-mean circulation responses – upward motion and horizontal-temperature advection, respectively. Transient eddy heat flux divergence plays an increasingly important role with latitude, becoming the main circulation response at high latitudes. However, this mechanism is less efficient at balancing heating perturbations than temperature advection, leading to greater reliance on an additional contribution from radiative cooling. These dynamical and radiative adjustments promote stronger lower-tropospheric warming in response to surface heating at high latitudes compared to lower latitudes. This elucidates the mechanisms by which sea ice loss contributes to polar amplification in a warming climate.