Recorded presentation7.2
An examination of diurnal cycle characteristics in the Experimental Climate Prediction Center’s global spectral models
A. Ruane, SIO/Univ. Of California, La Jolla, CA; and J. Roads and M. Kanamitsu
The Coordinated Enhanced Observing Period (CEOP) provides a new forum to access output from model and satellite products as well as in situ observations on diurnal time scales. Using the Tropical Rainfall Measuring Mission (TRMM) satellite’s precipitation record as well as CEOP station gauge data, we examine the Experimental Climate Prediction Center (ECPC)’s Global Spectral Model (GSM)’s ability to reproduce the global water and energy diurnal cycles. By separating individual components of the water and energy balances, we can identify variables that dominate the local balances in the models and note regions of similar characteristics. In general, the relative magnitude and phase of each variable’s least-squares-fit diurnal harmonic adjusts seasonally, in qualitative accordance with CEOP and TRMM observations, although there are certain times, especially over midlatitude summer regions, where the precipitation diurnal phase errors are large. Using CEOP in situ observations, we can show that some of the diurnal precipitation phase error can be attributed to diurnal evaporation errors. There are obviously other possible contributions to the phase errors. In addition to exploring the roles of different geographic influences over the continents, we have also found a strong land-sea contrast in phase and relative amplitude that appears in our models. This contrast may be overly influenced by the fixed sea surface temperature variations used to force the model, which suggests that coupled ocean-atmosphere models as well as oceanic observations may eventually be needed to fully explain land-sea geographic variations in the diurnal cycle. Recorded presentation
Session 7, Development of In Situ, Satellite, and Model Data Focused on Hydrometeorological Processes in the Atmosphere and Land Surface (parallel with Session 6)
Tuesday, 11 January 2005, 1:30 PM-5:30 PM
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