Tis study investigates the small-scale variations and covariations of cloud microphysical properties, namly, cloud liquid water content and cloud droplet number concentration, in marine boundary layer clouds based on in situ observation from the ACE-ENA campaign. We discuss the dependence of cloud variations on vertical location in cloud and the implications for warm rain simulations in the global climate models.
Tis study investigates the small-scale variations and covariations of cloud microphysical...
Review status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.
Vertical Dependence of Horizontal Variation of Cloud Microphysics: Observations from the ACE-ENA field campaign and implications for warm rain simulation in climate models
1Physics Department, University of Maryland Baltimore County (UMBC), Baltimore, 21250, USA
2Joint Center for Earth Systems Technology, UMBC, Baltimore, 21250, USA
3Department of Geography and Atmospheric Science, University of Kansas, Lawrence, 66045, USA
4Department of Mathematical Sciences, University of Wisconsin – Milwaukee, Milwaukee, 53201, USA
5Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, 63130, USA
6Environmental and Climate Science Department, Brookhaven National Laboratory, Upton, 11973, USA
7Joint Institute for Regional Earth System Science and Engineering, University of California Los Angeles, Los Angeles, 90095, USA
8Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 91011, USA
9Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, 85721, USA
10Pacific Northwest National Laboratory, Richland, WA 99354, USA
1Physics Department, University of Maryland Baltimore County (UMBC), Baltimore, 21250, USA
2Joint Center for Earth Systems Technology, UMBC, Baltimore, 21250, USA
3Department of Geography and Atmospheric Science, University of Kansas, Lawrence, 66045, USA
4Department of Mathematical Sciences, University of Wisconsin – Milwaukee, Milwaukee, 53201, USA
5Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, 63130, USA
6Environmental and Climate Science Department, Brookhaven National Laboratory, Upton, 11973, USA
7Joint Institute for Regional Earth System Science and Engineering, University of California Los Angeles, Los Angeles, 90095, USA
8Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 91011, USA
9Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, 85721, USA
10Pacific Northwest National Laboratory, Richland, WA 99354, USA
Received: 29 Jul 2020 – Accepted for review: 01 Aug 2020 – Discussion started: 11 Aug 2020
Abstract. In the current global climate models (GCM), the nonlinearity effect of subgrid cloud variations on the parameterization of warm rain process, e.g., the autoconversion rate, is often treated by multiplying the resolved-scale warm ran process rates by a so-called enhancement factor (EF). In this study, we investigate the subgrid-scale horizontal variations and covariation of cloud water content (qc) and cloud droplet number concentration (Nc) in marine boundary layer (MBL) clouds based on the in-situ measurements from a recent field campaign, and study the implications for the autoconversion rate EF in GCMs. Based on a few carefully selected cases from the field campaign, we found that in contrast to the enhancing effect of qc and Nc variations that tends to make EF > 1, the strong positive correlation between qc and Nc results in a suppressing effect that makes tends to make EF < 1. This effect is especially strong at cloud top where the qc and Nc correlation can be as high as 0.95. We also found that the physically complete EF that accounts for the covariation of qc and Nc has a robust decreasing trend from cloud base to cloud top. Because the autoconversion process is most important at the cloud top, this vertical dependence of EF should be taken into consideration in the GCM parametrization scheme.
Tis study investigates the small-scale variations and covariations of cloud microphysical properties, namly, cloud liquid water content and cloud droplet number concentration, in marine boundary layer clouds based on in situ observation from the ACE-ENA campaign. We discuss the dependence of cloud variations on vertical location in cloud and the implications for warm rain simulations in the global climate models.
Tis study investigates the small-scale variations and covariations of cloud microphysical...