Preprints
https://doi.org/10.5194/egusphere-2023-3013
https://doi.org/10.5194/egusphere-2023-3013
10 Jan 2024
 | 10 Jan 2024

Use of multiple reference data sources to cross validate gridded snow water equivalent products over North America

Colleen Mortimer, Lawrence Mudryk, Eunsang Cho, Chris Derksen, Mike Brady, and Carrie Vuyvich

Abstract. We use snow course and airborne gamma data available over North America to compare the validation of gridded snow water equivalent (SWE) products when evaluated with one reference dataset versus the other. We assess product performance across both non-mountainous and mountainous regions, determining the sensitivity of relative product rankings and absolute performance measures. In non-mountainous areas, product performance is insensitive to the choice of SWE reference dataset (snow course or airborne gamma): the validation statistics (bias, unbiased root mean squared error, correlation) are consistent with one another. In mountainous areas, the choice of reference dataset has little impact on relative product ranking but a large impact on assessed error magnitudes (bias and unbiased root mean squared error). Further analysis indicates the agreement in non-mountainous regions occurs because the reference SWE estimates themselves agree up to spatial scales of at least 50 km, comparable to the grid spacing of most available SWE products. In mountain areas, there is poor agreement between the reference datasets even at short distances (< 5 km). We determine that differences in assessed error magnitudes result primarily from the range of SWE magnitudes sampled by each method, although their respective spatiotemporal distribution and elevation differences between the reference measurements and grid centroids also play a role. We use this understanding to produce a combined reference SWE dataset for North America, applicable for future gridded SWE product evaluations and other applications.

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Colleen Mortimer, Lawrence Mudryk, Eunsang Cho, Chris Derksen, Mike Brady, and Carrie Vuyvich

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2023-3013', Jeff Dozier, 14 Jan 2024
    • AC1: 'Reply on CC1', Colleen Mortimer, 24 May 2024
  • RC1: 'Comment on egusphere-2023-3013', Anonymous Referee #1, 17 Mar 2024
    • AC2: 'Reply on RC1', Colleen Mortimer, 24 May 2024
  • RC2: 'Comment on egusphere-2023-3013', Simon Gascoin, 17 Apr 2024
    • AC3: 'Reply on RC2', Colleen Mortimer, 24 May 2024
Colleen Mortimer, Lawrence Mudryk, Eunsang Cho, Chris Derksen, Mike Brady, and Carrie Vuyvich
Colleen Mortimer, Lawrence Mudryk, Eunsang Cho, Chris Derksen, Mike Brady, and Carrie Vuyvich

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Short summary
Ground measurements of snow water equivalent (SWE) are vital for understanding the accuracy of large-scale estimates from satellites and climate models. We compare two different types of measurements – snow courses and airborne gamma SWE estimates – and analyse how measurement type impacts the accuracy assessment of gridded SWE products. We use this analysis produce a combined reference SWE dataset for North America, applicable for future gridded SWE product evaluations and other applications.