14th Symposium on Global Change and Climate Variations


Sensitivity of land climate to leaf area index: role of surface conductance versus albedo

Katrina Hales, University of California, Los Angeles, CA; and J. D. Neelin and N. Zeng

Land climate sensitivities to surface properties are studied using an intermediate complexity tropical atmosphere model. We focus on land surface vegetation feedbacks to the atmosphere through the properties of surface conductance and albedo. Both are parameterized on leaf area index so that their relative impacts can be compared. For a given percent change in leaf area index, we find that low and moderate vegetation regions such as the Sahel have a higher sensitivity than rainforest regions such as the Amazon in both local total precipitation anomaly as well as fractional change in precipitation. Comparison of sensitivities to changes in surface conductance and albedo shows that neither is negligible and their relative influence differs among vegetation types. Rainforest regions are more influenced by surface conductance due to the large water recycling ratio there, while albedo has a larger influence in low vegetation regions by modifying the energy balance and large-scale atmospheric circulation. In moderate vegetation regions, altered surface conductance and albedo have comparable effects on precipitation. Surface conductance and albedo have opposing effects on surface temperature but the surface conductance has the dominant impact on both surface temperature and evapotranspiration.

Session 11, Surface/Atmosphere Interactions: II
Thursday, 13 February 2003, 8:30 AM-9:45 AM

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