Aerosol‐Cloud‐Precipitation Interactions in the Context of Convective Self‐Aggregation. (17th April 2019)

• Record Type: Journal Article
• Authors: Beydoun, H.; Hoose, C.
• Is Part Of: Journal of advances in modeling earth systems. Volume 11:Number 4(2019)
• Page Start: 1066
• Page End: 1087
• Publication Date: 2019-04-17
• Subjects: Geological modeling -- Periodicals; Climatology -- Periodicals; Geochemical modeling -- Periodicals; 551.5011
• DOI: 10.1029/2018MS001523
• Languages: English
• ISSNs: 1942-2466

Abstract

Abstract: We investigate the sensitivity of self‐aggregated radiative‐convective‐equilibrium cloud‐resolving model simulations to the cloud condensation nuclei (CCN) concentration. Experiments were conducted on a long (2, 000‐km × 120‐km) channel domain, allowing the emergence of multiple convective clusters and dry regions of subsidence. Increasing the CCN concentration leads to increased moisture in the dry regions, increased midlevel and upper level clouds, decreased radiative cooling, and decreased precipitation. We find that these trends follow from a decrease in the strength of the self‐aggregation as measured by the moist static energy (MSE) variance. In our simulations, precipitation is correlated, both locally and in total, with the distribution of MSE anomalies. We thus quantify changes in the adiabatic/diabatic contributions to MSE anomalies (Wing & Emanuel, 2014, https://doi.org/10.1002/2013MS000269 ) and relate those changes to changes in precipitation. Through a simple two‐column conceptual model, we argue that the reduction in precipitation can be explained thermodynamically by the reduction in mean net radiative cooling and mechanistically by the weakening of the area‐weighted radiatively driven subsidence velocity—defined as the ratio of the total radiative cooling over the dry regions and the static stability. We interpret the system's response to increasing CCN as a thermodynamically constrained realization of an aerosol indirect effect on clouds and precipitation. Key Points: Convective self‐aggregation weakens with increased CCN concentration Precipitation decrease follows from weakened convective self‐aggregation Precipitation response scales with the mean radiative cooling and the area‐weighted radiatively driven subsidence velocity