ARCTIC PRECIPITATION AND EVAPORATION - MODEL RESULTS AND OBSERVATIONAL ESTIMATES

Observational estimates of precipitation and evaporation over the Arct ic Ocean and its terrestrial watersheds are compared with correspondin g values from the climate model simulations of the Atmospheric Model I ntercomparison Project (AMIP). Estimates of Arctic regional mean preci pitation from several observational sources show considerable scatter, and the observational estimates based on gauge adjusted station data are considerably larger than the other observational estimates. While the AMIP model simulations of precipitation also show scatter, the ens emble mean of the models' precipitation exceeds even the higher (gauge -adjusted) observational estimates over the Arctic Ocean and its major watersheds. The difference between simulated precipitation and evapor ation (P - E), representing the net freshwater gain (runoff) by the su rface, also exceeds the observational estimates by 44%-83% over the Ar ctic Ocean and by generally smaller percentages over the terrestrial w atersheds. The ensemble model mean of the annual P - E exceeds the cor responding river discharges of the Ob and Mackenzie Rivers by 62% and 14%, respectively. The simulated P and E are highly correlated across the AMIP models, and the interannual (as well as the seasonal) variati ons of P and E are highly correlated in the output of most of the indi vidual models, implying a coupling of the regional P and E in the mode ls. The only formulational feature found to be common to the high-P (a nd high-E) models is the use of a specified rather than a computed soi l moisture. A preliminary examination of the reanalyses of the Nationa l Centers for Environmental Prediction shows that the differences betw een the reanalysis-derived P and E are closer to the observational est imates than are the AMIP estimates. However, the magnitudes of the rea nalysis-derived P and E, individually, are higher than the correspondi ng observational estimates.