Liquid and ice microphysics in the CSU general circulation model. Part II: Impact on cloudliness, the Earth`s radiation budget, and the general circulation of the atmosphere
- Colorado State Univ., Fort Collins, CO (United States)
A prognostic equation for the mass of condensate associated with large-scale cloudiness directly coupes the atmospheric moisture budget and radiation budget through interactive cloud amounts and cloud optical properties. We have compared the cloudiness, the top-of-the-atmosphere and surface radiation budgets, the radiative forcing of clouds, and the atmospheric general circulation simulated with general circulation model with and without a prognostic cloud parameterization. In the EAULIQ run, radiative effects of cloud water, cloud ice, and snow are considered; those of rain are omitted. Cloud optical depth and cloud infrared emissivity depend on cloud water, cloud ice, and snow paths predicted by a bulk cloud microphysics parameterization. In the CONTROL run, a large-scale condensation scheme is used. Cloud optical properties depend on mean cloud temperatures. Results are presented for January and July means. Comparisons with data from the International Satellite Cloud Climatology Project and the Earth Radiation Budget Experiment show that EAULIQ yields improved simulations of geographical distribution of cloudiness, top-of-the-atmosphere radiation budget, and longwave and shortwave cloud radiative forcings. Differences between EAULIQ and CONTROL are largest in the tropics and are mostly due to a decrease (in EAULIQ) in the amount and optical thickness of upper-tropospheric clouds. In particular, cold bias in outgoing longwave radiation and overestimation of planetary albedo obtained in the CONTROL run over the tropical convective regions are substantially reduced. Differences in radiative and latent heating rates between runs lead to some improvements in the atmospheric general circulation simulated by EAULIQ when compared to statistics for observed circulation. Compared to CONTROL, EAULIQ yields a warmer troposphere except below 8 km between 30{degrees}N and 30{degrees}S. Mean meridional circulation is significantly weakened in EAULIQ. 48 refs., 24 figs., 2 tabs.
- OSTI ID:
- 273948
- Journal Information:
- Journal of Climate, Vol. 9, Issue 3; Other Information: PBD: Mar 1996
- Country of Publication:
- United States
- Language:
- English
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