Abstract
In this report, simulated global climatologies of seasonal- and annual-average rates of evaporation (E), precipitation (P), and E minus P (EmP) are presented. These climatologies are computed from coupled model control run output that have been generated by four participating Coupled Model Intercomparison Project 2+ (CMIP2+) models, and that are stored on National Energy Research Scientific Computing Center (NERSC) data archives. For comparison, the simulated climatologies of E over ocean are accompanied by those computed from the Goddard Satellite-Based Surface Turbulent Fluxes – Version 2 (GSSTF-2) data set. Furthermore, simulated climatologies of E over land are contrasted against those derived from a sum of EmP and P provided, respectively, by the National Centers for Environmental Prediction - National Center for Atmospheric Research (NCEP-NCAR) Reanalysis and the Global Precipitation Climatology Project (GPCP). The global climatologies of P inferred from the coupled models are compared with those from GPCP. Finally, the simulated climatologies of EmP are compared to the difference between E and P computed from the data sets mentioned above.
We find, in all climatologies, that the globally integrated EmP is very small compared to E or P, which satisfies the physical constraint that E and P must nearly balance when the water cycle is globally averaged over seasonal and longer time scales. Also, the following features have been identified in all water cycle climatologies: the ITCZ and SPCZ; the monsoons of Asia, Australia, Central Africa, and the Amazon basin; the Northern Hemisphere mid-latitude storm tracks; the Southern Hemisphere circumglobal high-latitude storm track; and the major tropical-subtropical subsidence regions. On the other hand, there can be discrepancies in the placement, extent, and/or magnitude of these climatological features amongst the models and the comparison data sets. This is especially evident in the NCAR and Department of Energy (DOE) Parallel Climate Model (PCM), which has a double ITCZ about the equator.