A comparison of correction factors for the systematic gauge-measurement errors to improve the global land precipitation estimate

Abstract

Precipitation gauges are critical for assessing precipitation measurements at regional and global scales and are often used to adjust precipitation estimates from other instruments such as satellites. However, gauge-measured precipitation is affected by gauge-undercatch that is often larger for solid precipitation. In the present work, two popular gauge-undercatch correction factors (CFs) were compared: one utilizes a dynamic correction model and is used in the Global Precipitation Climatology Centre (GPCC) Monitoring product and the other one employs fixed monthly climatologies and is used in the Global Precipitation Climatology Project (GPCP) product. How the choice of CFs impacts the total precipitation estimates was quantified over land at seasonal, annual, regional, and global scales. The CFs were also compared as a function of the environmental variables used in their development such as near-surface air temperature, relative humidity, and wind speed. Results showed that the annual precipitation estimate from gauges (with no correction) can be biased by ∼ 9.61% over the global land (excluding Antarctica), although it varied depending on the season (from ∼ 6.80% in boreal summer to more than 12.33% in boreal winter), and the method used for gauge-undercatch correction. Interannual variations of CFs can be large, so the use of the fixed climatology CFs requires caution. Given their magnitudes and differences, choosing appropriate CFs has important implications in refining the water and energy budget calculations.