Seasonal and interannual variations of large-scale precipitation have been examined using the CMAP / GPCP merged analyses and the newly available TRMM Precipitation Radar (PR) observation data. First, 3-dimensional structure of the mean annual cycle of monthly precipitation is defined on a 5.0olat/lon grid over the tropical belt from 37oS - 37oN using the TRMM PR data for a 6-year period from 1998 to the present. Dominated by the seasonal migration of the Inter-Tropical Convergence Zone (ITCZ), global tropical precipitation is characterized by strong and deep convection over South America, Africa, and the Maritime-Continent where convection towers with mean rain rate of 0.5mm/day or higher reach a height of above 8km. Relatively weaker precipitation and shallower convection, meanwhile, are observed over the oceanic areas, especially over the eastern Pacific.

Precipitation anomaly patterns associated with the ENSO and other large-scale circulation patterns (e.g. NAO, AO and PNA) are then investigated using the 6-year TRMM data and the 25-year (1970-2003) merged analyses. Case studies are conducted to identify features associated with the evolution of the climate phenomena. Composite maps of anomalous precipitation associated with the high and low phases for each of the individual phenomenon and their combinations are then constructed. EOF analysis is finally performed for the monthly anomaly precipitation fields to examine spatial and temporal variation patterns associated with each mode. In particular, 3-dimensional structure of ENSO-induced precipitation anomaly is defined using the TRMM PR data which covers two ENSO events.

The seasonal and interannual variations of global large-scale precipitation observed in the merged analyses and the TRMM data are then compared to those in the precipitation fields produced by the NCEP/NCAR reanalysis and several selected climate models. Results of these comparisons will be reported at the conference.