Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

On the Importance of Gauge-Undercatch Correction Factors and Their Impacts on the Global Precipitation Estimates

Version 1 : Received: 5 June 2021 / Approved: 7 June 2021 / Online: 7 June 2021 (12:59:50 CEST)

A peer-reviewed article of this Preprint also exists.

Mohammad Reza Ehsani, Ali Behrangi, A comparison of correction factors for the systematic gauge-measurement errors to improve the global land precipitation estimate, Journal of Hydrology, Volume 610, 2022, 127884, ISSN 0022-1694, https://doi.org/10.1016/j.jhydrol.2022.127884. (https://www.sciencedirect.com/science/article/pii/S0022169422004590) 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. Keywords: Gauge undercatch; Global precipitation; GPCC; Legates; Fuchs; Water balance Mohammad Reza Ehsani, Ali Behrangi, A comparison of correction factors for the systematic gauge-measurement errors to improve the global land precipitation estimate, Journal of Hydrology, Volume 610, 2022, 127884, ISSN 0022-1694, https://doi.org/10.1016/j.jhydrol.2022.127884. (https://www.sciencedirect.com/science/article/pii/S0022169422004590) 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. Keywords: Gauge undercatch; Global precipitation; GPCC; Legates; Fuchs; Water balance

Journal reference: Journal of Hydrology 2022, 610
DOI: 10.1016/j.jhydrol.2022.127884

Abstract

Precipitation gauges are critical for measuring precipitation rates at regional and global scales and are often used to calibrate precipitation rates estimated from other instruments such as satellites. However, precipitation measured at the gauges is affected by gauge-undercatch that is often larger for solid precipitation. In the present work, two popular gauge-undercatch correction factors are assessed: one utilizes a dynamic correction model and is used in the Global Precipitation Climatology Centre (GPCC) Monitoring product and the other one employs a fixed climatology and is used in the Global Precipitation Climatology Project (GPCP) product. How much the choice of correction factors can impact the total estimate of precipitation was quantified over land at seasonal, annual, regional, and global scales. The correction factors are also compared as a function of the environmental variables used in their development, among those are near-surface air temperature, relative humidity, wind speed, elevation, and precipitation intensity. Results show that correction factors can increase the annual precipitation rate based on the gauges by ~9.5 % over the global land (excluding Antarctica), although this amount can vary from ~6.3% (in boreal summer) to more than 10% (in boreal winter), depending on the season and the method used for gauge-undercatch correction. Annual variations of correction factors can also be large, so the use of the fixed climatology correction factors requires caution. Given their magnitudes and differences, selection of appropriate correction factors can have important implications in refining the water and energy budget calculations.

Keywords

gauge-undercatch; correction factors; global precipitation; GPCC; Legates correction factor; Fuchs correction factor;

Subject

EARTH SCIENCES, Atmospheric Science

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