Across the western united states, predicting spring snowmelt from the mountains is necessary to understand how much water supply will be available in reservoirs come summer and if IT will be enough to…

Across the western united states, predicting spring snowmelt from the mountains is necessary to understand how much water supply will be available in reservoirs come summer and if IT will be enough to meet summer water demands and manage short term flood risk. Knowing the temperature profile of the snowpack is important to know when the snowpack will be warm enough to start melting. Currently, the snowpack temperature is estimated in models used by federal agencies including the national weather service (NWS) river forecast centers (rfcs) and US army corps of engineers (USACE) to inform reservoir models run by the bureau of reclamation (BOR). Currently, there is no successful operational method to observe snow temperature profiles. Thus, a major GAP in our ability to validate modeled snow temperature at watershed scales exists. This project proposes to demonstrate the use of an emerging method to collect snow temperature profiles to integrate into snowmelt models. Leveraging the success of the cooperative snow survey program, this project proposes the deployment of a non-contact infrared snow temperature profiler (STP) in conjunction with cooperative snow surveys in california (CA), nevada (NV), colorado (CO), and montana (MT). The STP is designed for use during manual snow surveys and is intended to be lowered directly in the hole left behind by federal snow samplers. This measurement alone will provide the snowpack temperature profile. When combined with the snow water equivalent and snow depth data collected from the federal sampler, IT allows the calculation of bulk cold content. Bulk cold content is a necessary parameter to calculate snowmelt rates, timing, and volume. Implementation of the cooperative snow temperature survey will span three years. The project will begin by continuing ongoing field testing (year 1). IT will then deploy the STP with over 10 snow survey partners in numerous watersheds supplying water to 12 BOR facilities (years 2-3). In year 1 we will use snow PIT observations alongside snow sampler holes in CA, MT, and CO to investigate how the sensor works in varying snow climates and snowpack characteristics. Years 2 and 3 will involve working directly with snow survey to deploy the sensors and collect vertical snow temperature observations during monthly snow surveys. These activities will progress the sensor to be ready for operational use. To implement the novel measurements of the vertical profile of snow temperatures into existing research and operational models, we will work with the california-nevada and colorado basin rfcs, M3WORKS (modeling group for the airborne snow observatories INC.), and the USACE to validate, and if possible, bias-correct or calibrate, modeled snow temperature. Ultimately, having a network of snow temperature observations CO-located with snow water equivalent observations will improve water supply forecast skill and water management decisions.