Blocking diversity: The distinct roles of diabatic heating

A wide range of stagnant circulation patterns have been referred to as atmospheric blocking. Conventional approach to categorize blocks typically based on blocks’ wave structures such as ridge, trough, dipole, etc. However, few efforts have been made to understand the wide range of diversity of the relative importance of dry and moist processes shaping up the blocks which we here refer as the “blocking diversity”. Climate modeling and prediction of blocking remain a big challenge, in part because of a lack of understanding for the blocking diversity with distinct contribution from dry and moist processes. In this work, we aim to make progress to this gap of knowledge by delineating observed blocking diversity by categorizing distinct roles of diabatic heating. For blocks featured by quasi-stationary ridge, we find that diabatic heating is detached from the blocking center and formulates a moisture ‘halo’ surrounding the blocks thereby enhancing the eddy forcing due to interior zonal wave activity flux. We hypothesize that the halo effect of diabatic heating is conducive to the persistence and slow propagation of Rossby wave packets. While for blocks featured by large-amplitude troughs, we hypothesize that diabatic heating is directly coupled with the blocking and renders a relatively faster propagation speed of blocks. To further assess the hypothesis, we will demonstrate numerical simulations using a moist two-layer quasi-geostrophic (QG) model. This study emphasizes that blocking diversity is associated with distinct configurations of diabatic heating, which has important implications for understanding the role of moisture process in the blocking lifecycle and a potential pathway for interpreting the blocking diversity.