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Aerosol effects on cloud cover as evidenced by ground‐based and space‐based observations at five rural sites in the United States
Author(s) -
Ten Hoeve John E.,
Augustine John A.
Publication year - 2016
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 - 10.1002/2015gl066873
Subject(s) - aerosol , environmental science , forcing (mathematics) , radiative forcing , cloud cover , atmospheric sciences , radiative transfer , satellite , meteorology , climatology , cloud computing , physics , geology , operating system , quantum mechanics , astronomy , computer science
Previous studies of the second aerosol indirect (lifetime) effect on cloud cover have estimated the strength of the effect without correcting for near‐cloud contamination and other confounding factors. Here we combine satellite‐based observations with a multiyear ground‐based data set across five rural locations in the United States to more accurately constrain the second indirect aerosol effect and quantify aerosol effects on radiative forcing. Results show that near‐cloud contamination accounts for approximately 40% of the satellite‐derived aerosol‐cloud relationship. When contamination is removed and the effect of meteorological covariation is minimized, a strong physical aerosol effect on cloud cover remains. Averaged over all stations and after correcting for contamination, the daytime solar and total (solar + IR) radiative forcing is −52 W/m 2 and −19 W/m 2 , respectively, due to both direct and indirect aerosol effects for aerosol optical depths ( τ ) between 0 and 0.3. Averaged diurnally, the average total radiative forcing is +16 W/m 2 .