Observing and Understanding the Variability of Water in Weather and Climate
17TH Conference on Hydrology


Evaluations of estimates of freshwater discharge from continents

Kevin E. Trenberth, NCAR, Boulder, CO; and A. Dai

Several new estimates of annual and monthly mean values of continental freshwater discharge into the individual and global oceans at 1 degree resolution are compared. While the best estimate is that calibrated with actual discharge gauge measurements, estimates based on the atmospheric moisture budget and the inferred evaporation E minus precipitation P, have potential through being able to provide time series. Atmospheric reanalyses from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and the European Centre for Medium Range Weather Forecasts (ECMWF) are used along with a snow melt model and a river routing model to estimate the continental discharge. The discharge and its latitudinal distribution implied by the observation-based runoff and the ECMWF reanalysis-based P-E agree well with the river-based estimates, whereas the discharge implied by the NCEP/NCAR reanalysis-based P-E has a negative bias. Tests are made using independent estimates of P and the implied E, as well as the requirement that P should exceed E over land except where surface flow allows otherwise, such as Southern California. Results suggest that the P-E data from reanalyses may be used to study the interannual to decadal variations in continental discharge.

extended abstract  Extended Abstract (132K)

Joint Session 2, Spatial and Temporal Variability of Water in All Its Phases: Part 2 (Joint with the Symposium on Observing and Understanding the Variability of Water in Weather and Climate and the 17th Conference on Hydrology)
Monday, 10 February 2003, 1:30 PM-5:30 PM

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