Understanding the environmental characteristics of frontal precipitation

Climatological studies have marked the important role of atmospheric fronts in the hydroclimate and water cycle of the Earth system, especially in the mid-latitudes. Precipitation associated with fronts is highly affected by the (spatially and temporally) co-existing weather systems with fronts such as atmospheric rivers (ARs) and mesoscale convective systems (MCSs) proved by previous studies. Current work discloses the environmental characteristics of frontal precipitation, which is less discussed, through analyzing the environmental variables including frontogenesis, moisture flux convergence (MFC), and convective available potential energy (CAPE) within the frontal zone. Results show that the extreme-precipitating fronts have higher mean positive frontogenesis and mean positive MFC than non-extreme-precipitating fronts. The study attempts to explicate the role of ARs and MCSs in frontal precipitation by analyzing the statistical distribution and cross-section in the cross-front direction of environmental variables of categorized fronts (co-occurring with ARs, MCSs, and both). There is a distinguishable shift of mean positive MFC distribution towards the high end when fronts co-occur with ARs (including both ARs and MCSs) compared with these with MCSs only, indicating the critical role of ARs in moisture transport to facilitate precipitation within the frontal zone. This work aims to highlight the environmental characteristics of fronts, especially those producing extreme precipitation, contributing to the theoretical understanding of precipitation from the perspective of weather phenomenon.