In this study, the relationship between the interannual variability of Arctic-midlatitude thermal gradient (AMG) and the winter atmospheric blocking frequency in the Ural region (UBF) is investigated in the ERA5 reanalysis product from 1940 to 2023. In particular, the paper focuses on the large-scale atmospheric circulation patterns associated with high UBF concomitant to weak AMG and vice versa, revisiting the more common and documented relationship connecting intense Ural blocking activity to strong AMG. Results show that displacements of the atmospheric blocking from the Ural region towards the Arctic lead to anomalous southerly thermal advections at polar latitudes and stronger AMG. On the other hand, high blocking frequency co-occurring in the Ural, Greenland and Chukotka regions lead to weaker AMG by limiting northward heat advections towards the Arctic region. These findings highlight a more complex picture of the role of subpolar atmospheric circulation in controlling the AMG.

Earth’s tropical and subtropical rainbands, such as Intertropical Convergence Zones (ITCZs) and monsoons, are complex systems, governed by both large-scale constraints on the atmospheric general circulation and regional interactions with continents and orography, and coupled to the ocean. Monsoons have historically been considered as regional large-scale sea breeze circulations, driven by land-sea contrast. More recently, a perspective has emerged of a Global Monsoon, a global-scale solstitial mode that dominates the annual variation of tropical and subtropical precipitation. This results from the seasonal variation of the global tropical atmospheric overturning and migration of the associated convergence zone. Regional subsystems are embedded in this global monsoon, localized by surface boundary conditions. Parallel with this, much theoretical progress has been made on the fundamental dynamics of the seasonal Hadley cells and convergence zones via the use of hierarchical modeling approaches, including aquaplanets. Here we review the theoretical progress made, and explore the extent to which these advances can help synthesize theory with observations to better understand differing characteristics of regional monsoons and their responses to certain forcings. After summarizing the dynamical and energetic balances that distinguish an ITCZ from a monsoon, we show that this theoretical framework provides strong support for the migrating convergence zone picture and allows constraints on the circulation to be identified via the momentum and energy budgets. Limitations of current theories are discussed, including the need for a better understanding of the influence of zonal asymmetries and transients on the large-scale tropical circulation.