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Regime‐based analysis of aerosol‐cloud interactions
Author(s) -
Gryspeerdt Edward,
Stier Philip
Publication year - 2012
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 - 10.1029/2012gl053221
Subject(s) - aerosol , sensitivity (control systems) , environmental science , satellite , cloud computing , atmospheric sciences , cloud fraction , climatology , meteorology , cloud cover , physics , geology , computer science , astronomy , electronic engineering , engineering , operating system
Previous global satellite studies into the indirect aerosol effect have relied on determining the sensitivity of derived Cloud Droplet Number Concentration (N d ) to co‐located Aerosol Optical Depth (AOD). These studies generally find a positive N d sensitivity to AOD changes over ocean, but some find a negative sensitivity over land, in contrast to that predicted by models and theory. Here we investigate the N d sensitivity to AOD in different cloud regimes, determined using a k‐means clustering process on retrieved cloud properties. We find the strongest positive N d sensitivity in the stratiform regimes over both land and ocean, providing the majority of the total sensitivity. The negative sensitivity previously observed over land is generated by the low cloud fraction regimes, suggesting that it is due to the difficulty of retrieving N d at low cloud fractions. When considering a mean sensitivity, weighted by liquid cloud fraction to account for sampling biases, we find an increased sensitivity over land, in some regions becoming positive. This highlights the importance of regime based analysis when studying aerosol indirect effects.