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Aerosol Indirect Effects in Marine Stratocumulus: The Importance of Explicitly Predicting Cloud Droplet Activation
Author(s) -
Bulatovic I.,
Ekman A. M. L.,
Savre J.,
Riipinen I.,
Leck C.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl081746
Subject(s) - marine stratocumulus , environmental science , liquid water path , aerosol , atmospheric sciences , meteorology , large eddy simulation , climate model , climatology , climate change , physics , turbulence , geology , ecology , biology
Climate models generally simulate a unidirectional, positive liquid water path (LWP) response to increasing aerosol number concentration. However, satellite observations and large‐eddy simulations show that the LWP may either increase or decrease with increasing aerosol concentration, influencing the overall magnitude of the aerosol indirect effect (AIE). We use large‐eddy simulation to investigate the LWP response of a marine stratocumulus cloud and its dependence on different parameterizations for obtaining cloud droplet number concentration (CDNC). The simulations confirm that the LWP response is not always positive—regardless of CDNC treatment. However, the AIE simulated with the model version with prescribed CDNC is almost 3 times larger compared to the version with prognostic CDNC. The reason is that the CDNC in the prognostic scheme varies in time due to supersaturation fluctuations, collection, and other microphysical processes. A substantial spread in simulated AIE may thus arise simply due to the CDNC treatment.