Effects of precipitation-bias corrections on surface hydrology over northern latitudes

Under-catch errors in precipitation gauge records can be as large as 50-100% during the cold season at high latitudes. To quantify the impacts of these errors on hydrometeorological fields, a comprehensive land surface model, namely the Community Land Model version 3 (CLM3), is run forced with (COF) and without (CON) precipitation-bias corrections and other identical atmospheric forcing from 1973 to 2004. It is found that the enhanced snowfall induced by the bias corrections increases snow accumulation on the ground (by 6-18 cm for December to February), which in turn increases May to July runoff by 0.4-0.6 mm day-1 and streamflow by 5-25% for most major rivers in the northern latitudes (north of 45 degrees N). The precipitation-bias corrections also improve the model-simulated mean annual cycle and temporal variations of streamflow for the major northern rivers during 1973-2004. As a result, the simulation of the freshwater discharge into the Arctic Ocean is also improved. Only small and statistically insignificant changes are found in soil moisture content, surface evaporation, and sensible heat flux between the CON and COF runs. Nevertheless, the results still suggest that it is important to use bias-corrected precipitation in terrestrial water balance analyses and land surface modeling.