Climatology of the Atmospheric Boundary Layer Height Using ERA5: Spatio-Temporal Variations and Controlling Factors

Geophysical processes within the atmospheric boundary layer (ABL) play important roles in the energy, momentum, and particle exchanges in the lower atmosphere. The height of the ABL top (ABL height; ABLH) decides the depth of these ABL processes. To better understand the spatio-temporal characteristics of the ABLH, the present study analyzed 45 years of global ABLH data retrieved from ERA5, in which the ABLH was defined using the bulk Richardson number, and the climatology of the ABLH was investigated. Further, the relationship between the ABLH and meteorological parameters was examined. High near-surface air temperature represents fair weather conditions that favor the ABL evolution, causing a high ABLH. In contrast, high precipitation represents bad weather conditions that restrain the ABL evolution, causing a low ABLH. The present study also studied the effects of synoptic weather systems, ocean–atmosphere interactions, terrains, and monsoon systems on the ABLH. Multiple controlling factors, including synoptic systems, cold ocean currents, terrain, and monsoons, influence the weather conditions and the complicated spatio-temporal distribution of the ABLH.