The Relationship of Low-Cloud Optical Depth to Temperature in ARM Observations With Implications for Cloud Feedbacks

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Description

In climate models, the relationship of low-cloud optical depth to temperature arising from variability within the current climate has been shown to be predictive of the long-term changes of low-cloud optical depth that result from greenhouse-induced global warming. This motivates efforts to use observations to better determine this relationship. Here ARM observations from the SGP, NSA and GRW are used to document how low-cloud optical depth varies with temperature in three different climate regimes spanning a wide range of temperature. Observations of cloud-physical thickness, and liquid water path and content are also used to ascertain which cloud properties contribute to the relationship of optical-depth with temperature. These findings are then used to assess the dependence of low-cloud optical depth on temperature simulated in CMIP3 and CMIP5 model outputs at ARM sites. This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-648655.