Publication linked here: We evaluated fine-scale changes in the magnitude and duration of alpine snow water storage and release by comparing effective precipitation seasonality to that of surface water inputs using a Snow Storage Index (SSI). We forced the Distributed Hydrology Soil Vegetation Model with historical climate conditions and an end-of-century warming signal down-scaled from a 4-km regional climate model, to simulate future changes in snow water storage and partitioning of precipitation to runoff and evapotranspiration. The hydrological modeling was conducted on a 2-m spatial grid to resolve fine scale processes over a 0.6-km2 headwater catchment within the Niwot Ridge Long-Term Ecological Research site located in the Rocky Mountains, Colorado, USA. Proportionally more rainfall, reduced snowpack size and extent, and earlier snowmelt occurred in the future scenario with decreased catchment average SSI and thus snow water storing capabilities, with inordinately large decreases occurring in areas of the catchment with reconstructed snowdrifts (−57% average and −100% maximum). Using the Budyko framework to evaluate annual hydrologic partitioning, precipitation inputs to streamflow increased by a maximum 10% in large SSI regions with snowdrifts under warming conditions, signifying a potential buffer for total catchment and annual streamflow loss in a future climate (Hale et al., 2024).

Annual average Snow Storage Index compared to the Budyko anomaly per grid-cell, per eco-region across the western United States. All relationships are statistically significant (linear and Spearman rank p < 0.05). Shading represents the 95% confidence interval, and Variable Infiltration Capacity grid cells are colored by average annual aridity (PET/P). Corresponding slope, linear r2 values and Spearman rank correlation values (Rs) are listed in each panel. Positive Budyko anomalies indicate overproduction of streamflow, whereas negative Budyko anomalies indicate underproduction of streamflow. Black open circles indicate the Catchment Attributes and Meteorology for Large-Sample Studies data within each eco-region.

SnowEx was a multi-year NASA Terrestrial Hydrology Program field experiment to address important gaps in remote sensing of snow and snowpack-derived water resources. SnowEx focused on airborne technology and ground-based field work and on comparing various sensing approaches, with an ultimate goal of globally measuring snow water equivalent from space. SnowEx thus laid a groundwork for a future snow satellite mission. My responsibilities each snow season included: measuring snow pit profiles including density, temperature, stratigraphy, liquid water content, and specific surface area (SSA); completing snow depth transects; completing ground penetrating radar (GPR) grids and terrestrial LiDAR scans (TLS); analyzing raw data for public distribution and complementary research; maintaining automated snow sensor networks at field locations. These efforts took place across the mountainous western United States, including Niwot Ridge of the Front Range, Colorado and the North Slope of Alaska.

Publication linked here: As the climate warms, the fraction of precipitation falling as snow is expected to decrease and the timing of snowmelt is expected to shift earlier in spring. In snow-dominated mountainous regions that rely on snowpack and snowmelt for water supply, this change in snow accumulation and melt prompts us to examine downstream changes in streamflow. The objective of this study is to understand how changes in precipitation phase and snowmelt timing alter the timing of surface water inputs (i.e. rainfall and snowmelt) and the partitioning of these inputs between evapotranspiration and streamflow. Increased streamflow generation efficiency during winter months effectively buffered the net annual streamflow decline associated with warming. This cold season buffering effect is unique to snow influenced systems, as the magnitude and timing of water released from snowpacks, and input to the surface, is sensitive to warming whereas the timing and magnitude of surface water inputs in rain-dominated systems are insensitive to warming. Seasonal streamflow buffering may diminish as warming drives many systems toward rain-dominance and may have important implications for hydrological and ecological processes and for water resource management across Earth’s snow-influenced regions (Hale et al., 2022a).