Publication Abstracts

Friend and Kiang 2005

Friend, A.D., and N.Y. Kiang, 2005: Land surface model development for the GISS GCM: Effects of improved canopy physiology on simulated climate. J. Climate, 18, 2883-2902, doi:10.1175/JCLI3425.1.

A new physiology-based model of canopy stomatal conductance and photosynthesis is described and included in the latest version of the GISS GCM, ModelE1. The sub-model includes responses to atmospheric humidity and CO2 concentration, responses missing from previous GISS GCM land surface schemes. Measurements of moisture and CO2 fluxes over four egetation types are used to test and calibrate the sub-model. Photosynthetic leaf N is calibrated for each vegetation type from the flux measurements.

The new sub-model results in surface cooling over many regions previously too warm. Some warm biases of over 2°C are cooled by more than 0.5°C, including over central Eurasia, South America, western USA, and Australia. In addition, some regions that were previously too cool are warmed, such as northern Eurasia and the Tibetan Plateau. A number of precipitation biases are also reduced, particularly over South America (by up to 1 mm/day) and the oceanic ITCZs (by over ±1 mm/day); coastal West Africa becomes significantly wetter. Cloud cover increases over many land areas previously too clear. Higher absolute canopy conductances, and positive feedbacks with atmospheric humidity are largely responsible for the simulated vegetation influence on the atmosphere. High latitude climate changes through remote effects of increased tropical latent heating, resulting directly from improved characterization of tropical forest canopy conductance. Realistic representation of the stomatal control on land evaporation is critical for accurate simulation of atmospheric dynamics in the GISS GCM.