A004-0007
Evaluation of modeled aerosol-cloud interactions using data from the ORACLES and LASIC field campaigns

Monday, 7 December 2020
Poster
Calvin Howes1, Pablo E Saide1, Paquita Zuidema2, Jianhao Zhang3, Michael S Diamond4, Jenny P S Wong5, Steven G Howell6, Athanasios Nenes7, Mary Kacarab8, L. Ruby Leung9, Amie Nicole Dobracki10, Graham Feingold11, Sharon P Burton12, Richard Anthony Ferrare12, Johnathan W Hair12, Marta A Fenn13, Steffen Freitag6, Chongai Kuang14, Arthur J Sedlacek III15, Yang Zhang16 and Uin Janek17, (1)University of California Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, CA, United States, (2)University of Miami, Miami, FL, United States, (3)University of Miami, RSMAS, Miami, FL, United States, (4)University of Washington, Atmospheric Sciences, Seattle, WA, United States, (5)University of Toronto, Toronto, ON, Canada, (6)University of Hawaii at Manoa, Oceanography, Honolulu, HI, United States, (7)Swiss Federal Institute of Technology Lausanne, Laboratory of Atmospheric Processes and their Impacts, School of Architecture, Civil & Environmental Engineering, Lausanne, Switzerland, (8)University of California Riverside, Riverside, CA, United States, (9)Pacific Northwest National Laboratory, Richland, WA, United States, (10)University of Hawaii at Manoa, Honolulu, HI, United States, (11)NOAA ESRL CSL, Boulder, CO, United States, (12)NASA Langley Research Center, Hampton, VA, United States, (13)SSAI, Hampton, VA, United States, (14)Brookhaven National Laboratory, Environmental and Climate Sciences Department, Upton, NY, United States, (15)Brookhaven National Lab, Upton, NY, United States, (16)Northeastern University, Department of Civil and Environmental Engineering, Boston, United States, (17)Brookhaven National Laboratory, Upton, NY, United States
Abstract:
Aerosol-cloud interactions are both uncertain and important in global and regional climate models, and especially in the southeast Atlantic Ocean. This uncertainty in the region is largely due to two correlated factors—the expansive, bright, semi-permanent stratocumulus cloud deck and the fact that southern Africa is the largest source of biomass-burning aerosols in the world. We study this region using the WRF-Chem model with CAM5 aerosols and in situ observations from the ORACLES and LASIC field campaigns in August-October of 2016 through 2018. We compare aerosol and cloud properties to measure and improve model performance and expand upon observational findings of aerosol-cloud effects. Relevant comparison variables include aerosol number concentration, mean particle diameter and spread, CCN activation tendency, hygroscopicity, and cloud droplet number concentrations. Specifically, our approach is to analyze colocated model data along flight tracks to resolve aerosol-cloud interactions. Within and between single-day flights, there is high spatiotemporal variability that can get lost to large-scale averaging analyses. We have found that CCN is substantially under-represented in the model compared to observations. For a given aerosol number concentration, size, supersaturation and hygroscopicity, the model will consider fewer particles as CCN than observations indicate. We plan to explore this result further, diagnosing the model-observation differences more consistently and updating the model with more physically accurate values of aerosol size, concentration, or hygroscopicity based on observations. We will also intercompare multiple instrument platforms involved with the ORACLES and LASIC campaigns. With improved small-scale aerosol-cloud interactions, this work also shows promise to substantially improve that representation in climate models.
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