Surface‐Atmosphere Decoupling Prolongs Cloud Lifetime Under Warm Advection Due To Reduced Entrainment Drying

Abstract

Low clouds strongly cool the climate by reflecting substantial solar radiation back into space. However, they are not well simulated in climate models due to coarse resolutions and complex underlying physical processes. Enhancing our understanding of low-cloud behavior, especially marine boundary layer clouds (MBLCs), could help reduce uncertainties in climate projections (

Evaluation of Stratocumulus Evolution Under Contrasting Temperature Advections in CESM2 Through a Lagrangian Framework

“…For background FT moisture changes, we find a large drop and a subsequent slight increase in q 700 (Figure 2c). dq tends to increase sharply (Figure 2d), indicating that entrainment is drying clouds more efficiently (see the entrainment drying term in Equation 1 in H. Zhang et al (2023)). Meanwhile, drying effects by subsidence tend to become weaker as ω 700 is decreasing (Figure 2e), resulting in less drying air being brought downward.…”

“…Compared to CADV, the decoupling in WADV, that is, suppressed surface fluxes, tends to prolong the persistence of Sc decks, as observed by Zheng and Li (2019). The mechanism was revealed by H. Zhang et al (2023) using large-eddy simulations (LESs), finding that reduced entrainment drying due to decoupling helps sustain cloud decks in WADV. Due to different decoupling features, Sc cloud responses to environmental factors also exhibit distinct behaviors between CADV and WADV conditions.…”

“…The mechanism was revealed by H. Zhang et al. (2023) using large‐eddy simulations (LESs), finding that reduced entrainment drying due to decoupling helps sustain cloud decks in WADV. Due to different decoupling features, Sc cloud responses to environmental factors also exhibit distinct behaviors between CADV and WADV conditions.…”

“…Due to different decoupling features, Sc cloud responses to environmental factors also exhibit distinct behaviors between CADV and WADV conditions. H. Zhang et al (2023) found that cloud lifetime is more sensitive to variations in FT moisture under WADV conditions compared to its cold counterpart as WADV-induced complete decoupling minimizes the surface forcing effects, yielding the dominant influence of FT moisture. These findings highlight the markedly distinct impacts of physical processes on cloud properties under two contrasting T adv conditions.…”

First Assessment of Cloud‐Land Coupling in LASSO Large‐Eddy Simulations

“…Meanwhile, cloud‐surface coupling is significant to cloud formation and development. By mediating the moisture and energy budget of the boundary layer, the coupling of low clouds with the surface affects boundary‐layer turbulent mixing, cloud‐top entrainment, precipitation, and related processes, which control cloud development (Dussen et al., 2014, 2015; Sandu et al., 2010; H. Zhang et al., 2023; Y.‐T. Zheng, Zhang, & Li, 2021, Zheng, Zhang, Rosenfeld, et al., 2021).…”