Effects of observationally validated cloud-radiation schemes in a general circulation model

Conference · Sat Nov 01 04:00:00 EST 1997

OSTI ID:535490

Somerville, R C.J.; Iacobellis, S F; Lee, Wan-Ho ^[1]

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1. Univ. of California, La Jolla, CA (United States)

This paper very briefly describes an investigation of the effects on climate sensitivity of several different cloud-radiation parameterizations and validations of the parameters with observations. A general circulation model developed from the National Center for Atmospheric Research Community Climate Models (CCM2 and CCM3) was used for the study. In addition to a relative humidity based scheme, four parameterizations incorporating prognostic cloud water were tested, both with and without interactive cloud radiative properties. The globally averaged net cloud forcing was negative in all model versions. The effects of interactive cloud-radiative properties on global climate sensitivity were highly significant. The net cloud-radiative feedbacks consist of quite different shortwave and longwave components between the schemes with interactive cloud radiative properties and those with specified properties. The increase in cloud water content in a warmer climate leads to optically thicker middle and low clouds and in turn to negative shortwave feedbacks for the interactive radiative schemes, while the decrease in cloud amount produces a positive shortwave feedback for the schemes with specified cloud water path. For the longwave feedbacks, the decrease in high effective cloudiness for the schemes without interactive radiative properties leads to a negative feedback, while for the other cases, the longwave feedback is positive. Comparisons with measurements suggest that schemes with explicit cloud water budgets and interactive radiative properties are potentially capable of matching observational data closely. 3 refs.

• DOE Contract Number: FG03-90ER61061
• OSTI ID: 535490
• Report Number(s): CONF-970207--; CNN: Grant NAG5-2238
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CLIMATE MODELS
CLIMATIC CHANGE
CLOUDS
OPTICAL PROPERTIES
SENSITIVITY ANALYSIS
THERMODYNAMIC PROPERTIES