COMPARISON OF TROPICAL OCEAN-ATMOSPHERE FLUXES WITH THE NCAR COMMUNITY CLIMATE MODEL CCM3

The properties of the marine boundary layer produced by the National C enter for Atmospheric Research (NCAR) Community Climate Model version 3 (CCM3) are compared with observations from two experiments in the ce ntral and western equatorial Pacific. The main objective of the compar ison is determining the accuracy of the ocean-atmosphere fluxes calcul ated by the model. The vertical thermodynamic structure and the surfac e fluxes calculated by the CCM3 have been validated against data from the Central Equatorial Pacific Experiment (CEPEX) and the Tropical Oce an Global Atmosphere-Tropical Atmosphere Ocean (TOGA-TAO) buoy array. The mean latent heat flux for the TOGA-TAO array is 92 W m(-2), and th e model estimate of latent flux is 109 W m(-2). The bias of 17 W m(-2) is considerably smaller than the overestimation of the Bur by the pre vious version of the CCM. The improvement in the latent heat flux is d ue to a reduction in the surface winds caused by nonlocal effects of a new convective parameterization. The agreement between the mean sensi ble heat flux for the TOGA-TAO array and the model estimate has also b een improved in the new version of the model. The current version of t he CCM overestimates the sensible heat flux by 3.4 W m(-2). The atmosp heric temperature and water vapor mixing ratio from the lowest model l ayer are within 0.3 K and 0.4 g kg(-1) of measurements obtained from r adiosondes. The mean model value of the boundary layer height is withi n 13 m of the average height derived from a Raman lidar on board a shi p in the CEPEX domain. There is some evidence that the biases in the m odel can be reduced further by modifying the bulk formulation of the s urface fluxes.