Hotspots of Efficient Large-scale Circulation Response to Idealized Diabatic Heating

Soil moisture anomalies can influence large-scale atmospheric circulation and thereby affect remote regions. However, the seasonal and geographical dependence of these circulation responses has been largely unexplored. Here, we conduct idealized experiments with a Linear Baroclinic Model, imposing identical low-level diabatic heating anomalies across global land to examine atmospheric circulation responses to persistent drought-like heating. Responses are generally strongest in winter, weakest in summer and are characterized by an upper-level anticyclonic anomaly displaced northeastward from the heating source, with the largest displacement in spring. Several hotspots emerge from our analysis: heating over the Great Plains, Tibetan Plateau, southeastern South America, and Australia produces substantially stronger circulation responses than heating elsewhere. These stronger responses are associated with enhanced vertical motion, reflecting strong low-level convergence and upper-level divergence. The hotspot regions are characterized by lower climatological static stability and enhanced warm advection. Warm advection is strongest when the imposed heating is located near elevated terrain and the upper-level jet, where strong temperature and circulation perturbations interact with intense upper-level westerlies. Perturbed temperature gradients contribute to the northeastward displacement of the upper-level response through thermal wind balance. Our results suggest that sustained heating in these hotspot regions can generate strong atmospheric circulation anomalies, providing a dynamical pathway for drought amplification and spatiotemporal propagation.