TY - JOUR
T1 - Environmental effects on aerosol-cloud interaction in non-precipitating marine boundary layer (MBL) clouds over the eastern North Atlantic
AU - Zheng, Xiaojian
AU - Xi, Baike
AU - Dong, Xiquan
AU - Wu, Peng
AU - Logan, Timothy
AU - Wang, Yuan
N1 - Funding Information:
study were obtained from the Atmospheric Radiation Measurement (ARM) program sponsored by the US Department of Energy (DOE) Office of Energy Research, Office of Health and Environmental Research, and Environmental Sciences Division. The data can be downloaded from https://adc.arm.gov/ discovery/#/results/site_code::ena (Atmospheric Radiation Measurement Data Center, 2021a). The reanalysis data were obtained from the ECMWF model output, which provides data explicitly for analysis at the ARM ENA site. The data can be downloaded from https://adc.arm.gov/discovery/#/results/datastream:: enaecmwfvarX1.c1 (Atmospheric Radiation Measurement Data Center, 2021b).
Funding Information:
Financial support. This research has been supported by the National Science Foundation (grant nos. AGS-1700728 and AGS-2031750) and the US Department of Energy, Office of Science, Office of Biological and Environmental Research, Earth System Model Development program (the “Enabling Aerosol-cloud interactions at GLobal convection-permitting scalES (EAGLES)” project (project no. 74358)).
Funding Information:
Acknowledgements. The ground-based measurements were obtained from the Atmospheric Radiation Measurement (ARM) Program sponsored by the US Department of Energy (DOE) Office of Energy Research, Office of Health and Environmental Research, and Environmental Sciences Division. The reanalysis data were obtained from the ECMWF model output, which provides data explicitly for analysis at the ARM ENA site. The data can be downloaded from https://adc.arm.gov/discovery/ (last access: 2 September 2021). This work was supported by the NSF grants AGS-1700728/1700727 and AGS-2031750/2031751 and was also supported as part of the “Enabling Aerosol-cloud interactions at GLobal convection-permitting scalES (EAGLES)” project (74358), funded by the US Department of Energy, Office of Science, Office of Biological and Environmental Research, Earth System Model Development program with a subcontract to the University of Arizona. The Pacific Northwest National Laboratory is operated for the Department of Energy by the Battelle Memorial Institute under contract DE-AC05-76 RL01830. And a special thanks goes to the editor Hang Su, Mikael Witte, and the two anonymous reviewers for their constructive comments and suggestions, which helped to improve the manuscript.
Publisher Copyright:
© Copyright:
PY - 2022/1/10
Y1 - 2022/1/10
N2 - Over the eastern North Atlantic (ENA) ocean, a total of 20 non-precipitating single-layer marine boundary layer (MBL) stratus and stratocumulus cloud cases are selected to investigate the impacts of the environmental variables on the aerosol-cloud interaction (ACIr) using the ground-based measurements from the Department of Energy Atmospheric Radiation Measurement (ARM) facility at the ENA site during 2016-2018. The ACIr represents the relative change in cloud droplet effective radius re with respect to the relative change in cloud condensation nuclei (CCN) number concentration at 0.2ĝ€¯% supersaturation (NCCN,0.2%) in the stratified water vapor environment. 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 effect of enhanced condensational growth and coalescence processes associated with higher Nc and PWVBL. The principal component analysis shows that the most pronounced pattern during the selected cases is the co-variations in the MBL conditions characterized by the vertical component of turbulence kinetic energy (TKEw), the decoupling index (Di), and PWVBL. The environmental effects on ACIr emerge after the data are stratified into different TKEw regimes. The ACIr values, under both lower and higher PWVBL conditions, more than double from the low-TKEw to high-TKEw regime. This can be explained by the fact that stronger boundary layer turbulence maintains a well-mixed MBL, strengthening the connection between cloud microphysical properties and the below-cloud CCN and moisture sources. With sufficient water vapor and low CCN loading, the active coalescence process broadens the cloud droplet size spectra and consequently results in an enlargement of re. The enhanced activation of CCN and the cloud droplet condensational growth induced by the higher below-cloud CCN loading can effectively decrease re, which jointly presents as the increased ACIr. This study examines the importance of environmental effects on the ACIr assessments and provides observational constraints to future model evaluations of aerosol-cloud interactions.
AB - Over the eastern North Atlantic (ENA) ocean, a total of 20 non-precipitating single-layer marine boundary layer (MBL) stratus and stratocumulus cloud cases are selected to investigate the impacts of the environmental variables on the aerosol-cloud interaction (ACIr) using the ground-based measurements from the Department of Energy Atmospheric Radiation Measurement (ARM) facility at the ENA site during 2016-2018. The ACIr represents the relative change in cloud droplet effective radius re with respect to the relative change in cloud condensation nuclei (CCN) number concentration at 0.2ĝ€¯% supersaturation (NCCN,0.2%) in the stratified water vapor environment. 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 effect of enhanced condensational growth and coalescence processes associated with higher Nc and PWVBL. The principal component analysis shows that the most pronounced pattern during the selected cases is the co-variations in the MBL conditions characterized by the vertical component of turbulence kinetic energy (TKEw), the decoupling index (Di), and PWVBL. The environmental effects on ACIr emerge after the data are stratified into different TKEw regimes. The ACIr values, under both lower and higher PWVBL conditions, more than double from the low-TKEw to high-TKEw regime. This can be explained by the fact that stronger boundary layer turbulence maintains a well-mixed MBL, strengthening the connection between cloud microphysical properties and the below-cloud CCN and moisture sources. With sufficient water vapor and low CCN loading, the active coalescence process broadens the cloud droplet size spectra and consequently results in an enlargement of re. The enhanced activation of CCN and the cloud droplet condensational growth induced by the higher below-cloud CCN loading can effectively decrease re, which jointly presents as the increased ACIr. This study examines the importance of environmental effects on the ACIr assessments and provides observational constraints to future model evaluations of aerosol-cloud interactions.
UR - http://www.scopus.com/inward/record.url?scp=85123411097&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85123411097&partnerID=8YFLogxK
U2 - 10.5194/acp-22-335-2022
DO - 10.5194/acp-22-335-2022
M3 - Article
AN - SCOPUS:85123411097
VL - 22
SP - 335
EP - 354
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
SN - 1680-7316
IS - 1
ER -