| 08 May 2026
A multi-decadal climatology of dust-on-snow from wet deposition in the Upper Colorado River Basin
Abstract. Dust-on-snow deposition is the dominant factor in earlier snowmelt timing in the Upper Colorado River Basin (UCRB), which gets ~70 % of its annual streamflow from snowmelt. Previous studies have demonstrated the radiative effects of dust-on-snow deposition, but have not quantified what deposition types, whether from atmospheric turbulence (dry deposition) or hydrometeor scavenging (wet deposition), drive these radiative effects. Here, we produce a climatology of the total amount and type of dust-on-snow deposition in the UCRB using the Modern-Era Retrospective analysis for Research and Applications (MERRA-2) reanalysis dataset from 1980–2023 and evaluate its accuracy using Surface Atmosphere Integrated Laboratory (SAIL) field measurements taken in 2022 and 2023 and Moderate Resolution Imaging Spectrometer (MODIS) Snow Property Inversion from Remote Sensing (SPIReS) dust concentration data. The results show that wet deposition is the dominant form of dust-on-snow deposition in the UCRB, comprising 73.8 % of total dust deposition. Additionally, the eastern areas in the UCRB, particularly the Gunnison Watershed, experience 16 % higher wet deposition monthly totals (69.33 mg m-2) than the entire UCRB average (59.80 mg m-2). These results highlight the importance of persistent spatial patterns but also interannual variability in accounting for dust deposition. This climatology also contextualizes the long-term records of dust deposition by showing how the relationships between dust at several sites with decadal records project onto the entire Basin, while also supporting water resource planning, especially for areas with elevated wet deposition levels.
This paper studies the dust-on-snow deposition in the Upper Colorado River Basin. Varied periods and datasets were used, since the MERRA-2 dataset was considered from 1980 to 2023. However, field measurements extended from 2022 to 2023 together with MODIS and SPIReS dust concentration data. Since the paper handles a noticeable amount of information and it is focused on a quite specialised issue, only some minor changes should be considered.
The study considers a limited number of events in the years 2022 and 2023 from available measurements. Since the authors highlight the interannual variability of dust deposition, they should comment the study representativeness.
Most of the analysis refers to spring. However, Figure 5 considers the period November-May and the period February-June is used in Figure 6. A comment about the selection of these varied periods would be acknowledged. Moreover, the authors should justify if comparisons are possible with these varied periods.
Figure 4 indicated that the spatial analysis for dry deposition led to similar values and it could be ignored since the wet deposition determines the spatial distribution. The authors should underline the convenience of this analysis based on wet and dry deposition.
Some references are a bit old. The authors should clarify if the lack of recent references could be due to the lack of research interest about this issue. Moreover, potential readers would acknowledge the increase of recent references in the discussion section to compare the results of this paper with previous studies.
Minor remarks.
Equation (1) should be revised.
Figure 5. Dot in blue should be in red in the figure (or in blue in the legend). The same colour should go in all the figures.
Reference Randles et al. should be revised.