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  • Environmental effects on aerosol–cloud interaction in non-precipitating marine boundary layer (MBL) clouds over the eastern North Atlantic
Title: Environmental effects on aerosol–cloud interaction in non-precipitating marine boundary layer (MBL) clouds over the eastern North Atlantic
Abstract. Over the eastern North Atlantic (ENA) ocean, a total of 20 non-precipitating single-layer marine boundary layer (MBL) stratus and stratocumuluscloud cases are selected to investigate the impacts of the environmental variables on the aerosol–cloud interaction (ACIr) using theground-based measurements from the Department of Energy Atmospheric Radiation Measurement (ARM) facility at the ENA site during 2016–2018. TheACIr represents the relative change in cloud droplet effective radius re with respect to the relative change in cloudcondensation nuclei (CCN) number concentration at 0.2 % supersaturation (NCCN,0.2 %) in the stratified water vaporenvironment. The ACIr values vary from −0.01 to 0.22 with increasing sub-cloud boundary layer precipitable water vapor (PWVBL)conditions, indicating that re is more sensitive to the CCN loading under sufficient water vapor supply, owing to the combined effectof enhanced condensational growth and coalescence processes associated with higher Nc and PWVBL. The principal componentanalysis shows that the most pronounced pattern during the selected cases is the co-variations in the MBL conditions characterized by the verticalcomponent of turbulence kinetic energy (TKEw), the decoupling index (Di), and PWVBL. The environmental effects onACIr emerge after the data are stratified into different TKEw regimes. The ACIr values, under both lowerand higher PWVBL conditions, more than double from the low-TKEw to high-TKEw regime. This can be explained bythe fact that stronger boundary layer turbulence maintains a well-mixed MBL, strengthening the connection between cloud microphysical properties andthe below-cloud CCN and moisture sources. With sufficient water vapor and low CCN loading, the active coalescence process broadens the cloud dropletsize spectra and consequently results in an enlargement of re. The enhanced activation of CCN and the cloud droplet condensationalgrowth induced by the higher below-cloud CCN loading can effectively decrease re, which jointly presents as the increasedACIr. This study examines the importance of environmental effects on the ACIr assessments and provides observational constraintsto future model evaluations of aerosol–cloud interactions.  more » « less
Award ID(s):
2031751
PAR ID:
10359135
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
Atmospheric Chemistry and Physics
Volume:
22
Issue:
1
ISSN:
1680-7324
Page Range / eLocation ID:
335 to 354
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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