Cloud adjustments in response to aerosol based on large ensembles of LES and satellite data

Description

Our work focuses on the relationship between meteorological and aerosol variables that together shape the properties of low, warm cloud fields. We study cloud fields in the NE Pacific and NE Atlantic (ENA) using a combination of satellite- and surface-remote sensing, and large eddy simulation. Three key themes will be presented:

• Meteorological and aerosol co-variability drives cloud albedo susceptibility¹.
  We identify the existence of both brightening and darkening susceptibility regimes and quantify their frequency of occurrence in different stratocumulus basins. Distinct regional and seasonal co-variabilities among meteorological factors play an important role in grouping conditions favorable for each susceptibility regime. Implications for marine cloud brightening will be discussed.
• Impacts of mesoscale cloud organization on aerosol-induced cloud water adjustment and cloud brightness².
  We analyze satellite-based observations of closed mesoscale cellular convection (MCC) across different sizes (8, 16, 32, and 64 km) to show that MCC cell-size plays a nontrivial role in regulating aerosol-induced cloud brightness via cloud water adjustment. In primarily non-precipitating cells, the cloud water adjustment to aerosol perturbations can be ten times more negative than in large-scale MCCs, consistent with stronger evaporation via cloud-top entrainment. This has a strong impact on cloud albedo susceptibility as a function of MCC scale.
• Large ensemble of LES to address the diurnal cycle of liquid water and cloud fraction adjustments³.
  We build and analyze an ensemble of more than 300 stratocumulus LESs to extend our knowledge of aerosol-induced changes in LWP and cloud fraction over a full diurnal cycle. We find distinct diurnal cycles in LWP and cloud fraction for coupled vs. decoupled cases. During the day when the boundary layer is overall more decoupled and turbulence is weaker, entrainment still plays an important role in LWP evolution, and the enhancement of entrainment associated with higher droplet number concentration is still detectable. Further analyses pertaining to stratocumulus systems will be presented at the meeting.

1. Zhang, J., and G. Feingold, 2023: Distinct regional meteorological influences on low-cloud albedo susceptibility over global marine stratocumulus regions. Atmos. Chem. Phys., https://doi.org/10.5194/acp-23-1073-2023.
2. Zhou, X., and G. Feingold, 2023: Impacts of Mesoscale Cloud Organization on Aerosol-induced Cloud Water Adjustment and Cloud Brightness, Res. Lett., in review.
3. , Y.-S., T. Yamaguchi, F. Glassmeier, and G. Feingold, 2023: Large ensemble of large eddy simulations to explore the diurnal cycle of cloud liquid water and fraction adjustments. J. Atmos. Sci., in preparation.