Abstract
The combination of snowfall, snow water equivalent (SWE), and precipitation rate measurements from 39 snow telemetry (SNOTEL) sites in Alaska were used to assess the performance of various precipitation products from satellites, reanalysis, and rain gauges. Observation of precipitation from two water years (2018–2019) of a high-resolution radar/rain gauge data (Stage IV) product was also utilized to give insights into the scaling differences between various products. The outcomes were used to assess two popular methods for rain gauge undercatch correction. It was found that SWE and precipitation measurements at SNOTELs, as well as precipitation estimates based on Stage IV data, are generally consistent and can provide a range within which other products can be assessed. The time-series of snowfall and SWE accumulation suggests that most of the products can capture snowfall events; however, differences exist in their accumulation. Reanalysis products tended to overestimate snow accumulation in the study area, while the current combined passive microwave remote sensing products (i.e., IMERG-HQ) underestimate snowfall accumulation. We found that correction factors applied to rain gauges are effective for improving their undercatch, especially for snowfall. However, no improvement in correlation is seen when correction factors are applied, and rainfall is still estimated better than snowfall. Even though IMERG-HQ has less skill for capturing snowfall than rainfall, analysis using Taylor plots showed that the combined microwave product does have skill for capturing the geographical distribution of snowfall and precipitation accumulation; therefore, bias adjustment might lead to reasonable precipitation estimates. This study demonstrates that other snow properties (e.g., SWE accumulation at the SNOTEL sites) can complement precipitation data to estimate snowfall. In the future, gridded SWE and snow depth data from GlobSnow and Sentinel-1 can be used to assess snowfall and its distribution over broader regions.
Highlights
Accurate quantitative knowledge of the amount and distribution of precipitation, precipitation phase, and snowpack is important for global water cycle studies, hydrology, and water resource management
As sublimation tends to be small in cold regions, precipitation and snow accumulation plots should be fairly comparable during the accumulation phase
(this might have been due to minor gauge undercatch for snow telemetry (SNOTEL)-PG or slight overestimation by SNOTEL-snow water equivalent (SWE) at this site); (5) At peak SWE, Global Precipitation Climatology Centre (GPCC)-L and GPCC-F (i.e., GPCC after applying gauge undercatch correction factors Correction factors (CFs)-L and CF-F, respectively) are closest to SNOTEL-SWE, followed by Global Precipitation Climatology Project (GPCP)
Summary
Accurate quantitative knowledge of the amount and distribution of precipitation, precipitation phase, and snowpack is important for global water cycle studies, hydrology, and water resource management. Using the observation of mass change from the Gravity Recovery and Climate Experiment (GRACE), [24] calculated snowfall accumulation over cold regions in the northern hemisphere and used the values to assess two popular gauge-undercatch correction factors (CFs): Legates climatology (CF-L), utilized in GPCP, and Fuchs dynamic correction model (CF-F), used in the Global Precipitation Climatology Centre (GPCC). The application of GRACE over mountainous regions and glaciers is complicated due to the coarse resolution and issues related to ice age rebound and glacier dynamics [27] Another approach could be to use the observation of snow water equivalent (SWE), because during the snow accumulation period SWE and snowfall are well connected (Broxton et al, 2016a).
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