On the simulations of global oceanic latent heat flux in the CMIP5 multimodel ensemble

Abstract

Simulations of the global oceanic latent heat flux (LHF) in the CMIP5 multimodel ensemble (MME) were evaluated in comparison with 11 LHF products. The results show that the mean state of LHF in the MME coincides well with that in the observations, except for a slight overestimation in the tropical regions. The reproduction of the seasonal cycle of LHF in the MME is in good agreement with that in the observations. However, biases are relatively obvious in the coastal regions.Aprominent upward trend in global-mean LHF is confirmed with all of the LHF products during the period of 1979-2005. Despite the consistent increase of LHF in CMIP5 models, the rates of increase are much weaker than those in the observations, with an average of approximately one-ninth that in the observations. The findings show that the rate of increase of nearsurface specific humidity qa inMMEis nearly 6 times that in the observations, while the rate of increase of the near-surface wind speed U is less than one-half that in the observations. The faster increase of qa and the slower increase of U could both suppress evaporation, and thus latent heat released by the ocean, which may be one of the reasons that the upward trend of LHF in the MME is nearly one order of magnitude lower than that in the observations.