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External Influences on Modeled and Observed Cloud TrendsUnderstanding the cloud response to external forcing is a major challenge for climate science. This crucial goal is complicated by intermodel differences in simulating present and future cloud cover and by observational uncertainty. This is the first formal detection and attribution study of cloud changes over the satellite era. Presented herein are CMIP5 (Coupled Model Intercomparison Project - Phase 5) model-derived fingerprints of externally forced changes to three cloud properties: the latitudes at which the zonally averaged total cloud fraction (CLT) is maximized or minimized, the zonal average CLT at these latitudes, and the height of high clouds at these latitudes. By considering simultaneous changes in all three properties, the authors define a coherent multivariate fingerprint of cloud response to external forcing and use models from phase 5 of CMIP (CMIP5) to calculate the average time to detect these changes. It is found that given perfect satellite cloud observations beginning in 1983, the models indicate that a detectable multivariate signal should have already emerged. A search is then made for signals of external forcing in two observational datasets: ISCCP (International Satellite Cloud Climatology Project) and PATMOS-x (Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmospheres - Extended). The datasets are both found to show a poleward migration of the zonal CLT pattern that is incompatible with forced CMIP5 models. Nevertheless, a detectable multivariate signal is predicted by models over the PATMOS-x time period and is indeed present in the dataset. Despite persistent observational uncertainties, these results present a strong case for continued efforts to improve these existing satellite observations, in addition to planning for new missions.
Document ID
20150023378
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Marvel, Kate
(Columbia Univ. New York, NY, United States)
Zelinka, Mark
(Lawrence Livermore National Lab. Livermore, CA, United States)
Klein, Stephen A.
(Lawrence Livermore National Lab. Livermore, CA, United States)
Bonfils, Celine
(Lawrence Livermore National Lab. Livermore, CA, United States)
Caldwell, Peter
(Lawrence Livermore National Lab. Livermore, CA, United States)
Doutriaux, Charles
(Lawrence Livermore National Lab. Livermore, CA, United States)
Santer, Benjamin D.
(Lawrence Livermore National Lab. Livermore, CA, United States)
Taylor, Karl E.
(Lawrence Livermore National Lab. Livermore, CA, United States)
Date Acquired
December 18, 2015
Publication Date
February 3, 2015
Publication Information
Publication: Journal of Climate
Publisher: AMS
Volume: 28
Issue: 12
Subject Category
Meteorology And Climatology
Earth Resources And Remote Sensing
Report/Patent Number
GSFC-E-DAA-TN21570
Funding Number(s)
CONTRACT_GRANT: NNX14AB99A
Distribution Limits
Public
Copyright
Other
Keywords
clouds (meteorology)
satellite observation
multivariate statistical analysis

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