Abstract
Abstract. Snow water equivalent (SWE) is an important variable in describing global seasonal snow cover. Traditionally, SWE has been measured manually at snow transects or using observations from weather stations. However, these measurements have a poor spatial coverage, and a good alternative to in situ measurements is to use spaceborne passive microwave observations, which can provide global coverage at daily timescales. The reliability and accuracy of SWE estimates made using spaceborne microwave radiometer data can be improved by assimilating radiometer observations with weather station snow depth observations as done in the GlobSnow SWE retrieval methodology. However, one possible source of uncertainty in the GlobSnow SWE retrieval approach is the constant snow density used in modelling emission of snow. In this paper, three versions of spatially and temporally varying snow density fields were implemented using snow transect data from Eurasia and Canada and automated snow observations from the United States. Snow density fields were used to post-process the baseline GlobSnow v.3.0 SWE product. Decadal snow density information, i.e. fields where snow density for each day of the year was taken as the mean calculated for the corresponding day over 10 years, was found to produce the best results. Overall, post-processing GlobSnow SWE retrieval with dynamic snow density information improved overestimation of small SWE values and underestimation of large SWE values, though underestimation of SWE values larger than 175 mm was still significant.
Highlights
Snow water equivalent (SWE) is an important property of the seasonal snow cover, and estimates of SWE are required in many hydrological and climatological applications, including climate model evaluation (Mudryk et al, 2018) and forecasting freshwater availability
Many passive microwave radiometer-based approaches for estimating SWE are adopted from an algorithm proposed by Chang and Foster (1987) for estimating snow depth from horizontally polarized Scanning Multichannel Microwave Radiometer (SMMR) measurements
Decadal, and multi-decadal versions of snow density fields were produced for Eurasia for the years 2000–2009
Summary
Snow water equivalent (SWE) is an important property of the seasonal snow cover, and estimates of SWE are required in many hydrological and climatological applications, including climate model evaluation (Mudryk et al, 2018) and forecasting freshwater availability. The limited spatial and temporal coverages of the ground-based measurements, especially in northern and alpine regions, limit the quality of estimates (Broxton et al, 2016; Mortimer et al, 2020). An alternative approach for estimating SWE is to use satellite measurements as they can provide global spatial coverage and good temporal resolution. Spaceborne passive microwave radiometer (for example Chang and Foster, 1987; Kelly et al, 2003; Pulliainen, 2006) or active radar (for example Lievens et al, 2019; Rott et al, 2010) observations can be used for retrieving SWE information. Many passive microwave radiometer-based approaches for estimating SWE are adopted from an algorithm proposed by Chang and Foster (1987) for estimating snow depth from horizontally polarized Scanning Multichannel Microwave Radiometer (SMMR) measurements. The algorithm is based on the difference in measured brightness
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