A global climate model (GENESIS) with a land-surface transfer scheme (LSX). Part II: CO{sub 2} sensitivity
- National Center for Atmospheric Research, Boulder, CO (United States)
The sensitivity of the equilibrium climate to doubled atmospheric CO{sub 2} is investigated using the GENESIS global climate model version 1.02. The atmospheric general circulation model is a heavily modified version of the NCAR CCM1 and is coupled to a multicanopy lane-surface model (LSX); multilayer models of soil, snow, and sea ice; and a slab ocean mixed layer. Features that are relatively new in CO{sub 2} sensitivity studies include explicit subgrid convective plumes, PBL mixing, a diurnal cycle, a complex land-surface model, sea ice dynamics, and semi-Lagrangian transport of water vapor. The global annual surface-air warming in the model is 2.1{degrees}C, with global precipitation increasing by 3.3%. Over most land areas, most of the changes in precipitation are insignificant at the 5% level compared to interannual variability. Decreases in soil moisture in summer are not as large as in most previous models and only occur poleward of {approximately}55{degrees} in Siberia, northern CAnada, and Alaska. Sea ice area in September recedes by 62% in the Artic and by 43% in the Antarctic. The area of Northern Hemispheric permafrost decreases by 48%, while the the total area of Northern hemispheric snowcover in January decreases by 48%, while the total area of Northern Hemispheric snowcover in January decreases by on 13%. The effects of several modifications to the model physics are described. Replacing LSX and the multilayer soil with a single-layer bucket model causes little change to CO{sub 2} sensitivities on global scales, and the regions of summer drying in northern high latitudes are reproduced, although with somewhat greater amplitude. Compared to convective adjustment, penetrative plume convection increases the tropical Hadley Cell response but decreases the global warming slightly by 0.1{degrees} to 0.3{degrees}, contrary to several previous GCM studies in which penetrative convection was associated with greater CO{sub 2} warming. 60 refs., 20 figs., 3 tabs.
- OSTI ID:
- 95951
- Journal Information:
- Journal of Climate, Vol. 8, Issue 5; Other Information: PBD: May 1995
- Country of Publication:
- United States
- Language:
- English
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