Bias correction of daily precipitation measurements for Mongolia

Bias correction procedures derived from the World Meteorological Organization's solid precipitation measurement intercomparison dataset for the Tretyakov rain gauge were applied to 20 years of data from 31 meteorological stations in Mongolia. Daily corrections of precipitation biases from wind-induced undercatch, wetting loss, and evaporation loss were made. The bias (systematic error) from wind loss dominates at stations located in prairies and forests. Evaporation loss (caused by the evaporation of precipitation in the gauge before precipitation is measured) and wetting loss of precipitation both cause significant error in regions of low precipitation. Bias corrections suggest that gauge-measured annual precipitation was significantly underreported by 15(.)2 to 80(.)6 mm over the 20 years studied. Annual precipitation in Mongolia should be 17 to 42% higher than previously reported, particularly in forests and prairies. The correction factor (CF, corrected/gauge-measured precipitation) varies seasonally and is greater in winter and smaller in summer, primarily because of undercatch of snowfall due to Winds. There is clear seasonal variation in the absolute value of the bias correction and in each individual component of the correction. The spatial variation in the absolute correction matches the spatial distribution of gauge-measured precipitation. The value of CF decreases as gauge-measured annual precipitation increases, because precipitation changes, occurred mostly in summer. These results will be useful for hydrologic and climatic studies of mid-latitudes and arid/semi-arid regions. Copyright (C) 2004 John Wiley Sons, Ltd.