Integrated Perspectives on Clouds, Precipitation, and the Surface Energy Budget in the Colorado Rocky Mountains using Observation from SAIL and SPLASH

The Colorado River serves as a critical source of water for over 40 million people in the United States and Mexico, including the people of 30 federally-recognized tribes.  Approximately 70% of the water from the Colorado River is used to irrigate over 5.5 million acres of land that provide food to people around the nation and around the world.  The availability of this water, distributed between Colorado, Utah, New Mexico, Wyoming, California, Arizona, and Nevada is regulated through a complex series of agreements that dictate how much water can be used by individual entities.  Such availability has been strained in recent years based on rapidly declining water levels in regional reservoirs.

reservoir

A manmade lake that is created when a dam is built on a river. River water backs up behind the dam creating a reservoir.

Source: USGS Source

  This decline has been demonstrated to be the combined result of a regional basin drought, a warming climate, and increased consumption associated with the rapid expansion of western cities.  

Colorado River water levels are primarily driven by runoff from the winter snowpack.  As such, the headwater regions high in the mountains surrounding the watershed

watershed

An area of land that channels rainfall and snowmelt to creeks, streams, and rivers, and eventually flows to the lowest point in a basin.

Source: USGS Source

play a central and important role in determining the overall amount of water that makes it into the Colorado River annually.  That transition from snowfall to runoff includes the intersection of numerous physical processes that need to be monitored and understood to provide water managers with the best possible information and forecasts to aid their decision making.  In response to this critical need, the U.S. Department of Energy (DOE), National Oceanic and Atmospheric Administration (NOAA), and National Science Foundation (NSF) have deployed instrumentation to the East River watershed, near the town of Crested Butte, Colorado.  These sensor systems, deployed to support the Surface-Atmosphere Integrated field Laboratory (SAIL), the Study of Precipitation, the Lower Atmosphere, and Surface for Hydrometeorology (SPLASH) and the Sublimation of Snow (SOS) study, have collected information on snow and rain properties, the exchange of energy between the atmosphere and underlying surface, surface properties, and regional weather.  

In the current project, we will use these datasets to advance understanding of key meteorological and hydrometeorological processes in this important watershed.  This includes work to understand the distribution of precipitation in the East River Basin (ERB), both spatially and temporally, and relate these distributions to synoptic and other forcing mechanisms. Additionally, this will include work to understand microphysical processes observed over the ERB, including secondary ice production, processes supporting precipitation conversion efficiency, and the annual cycle of precipitation phase and the impact of precipitation properties on the surface energy budget. In the area of lower-atmospheric stratification

stratification

Stratification refers to layers in rocks, soil, large bodies of water, and the atmosphere.

Source: Study.com Source

and circulations, the team will pursue research to connect synoptic forcing and associated cloud cover to atmospheric boundary layer structure and the development of localized flow regimes, including density- driven drainage flows, and convection-driven up-valley flows. We will also assess the extent to which ERB drainage flows follow classical models for one-dimensional katabatic wind regimes. Finally, we plan to conduct detailed analysis on the drivers of the surface energy budget in this area of complex topography.

topography

The land's physical attributes within a specific area or region, comprising both natural formations like mountains, valleys, and rivers, alongside human-made additions such as roads and buildings.

Source: Source

This includes work to better understand the drivers of changes in snow albedo, including snow aging and deposition of pollutants, by using spectrally-resolved irradiance observations collected at several sites within the valley, and by leveraging drone-based measurements of albedo over the river structure collected during the spring 2022 snow melt period. Additionally, we will use high-resolution surface data to contribute to planned efforts to understand the scales and footprints associated with observed turbulent fluxes,

flux

The amount of some type of particle or energy crossing a unit area per unit time.

Source: NRC Library Source

and the advective influence on such fluxes. Finally, we plan to leverage links between cloud cover and radiative terms of the surface energy budget to better understand and classify surface energy budget drivers of lower-atmospheric stability in this high-altitude mountain valley. 

This work will leverage data from the three different projects discussed above.  We will focus on data collected as part of SAIL by the U.S. DOE Atmospheric Radiation Measurement (ARM) program and the NOAA Physical Sciences Laboratory (PSL). Understanding gained through this work will be translated into numerical prediction tools that produce projections across a wide variety of timescales (weather to climate) through collaborations advanced by our team with colleagues at national laboratories working to develop and evaluate such modeling tools. Additionally, this work will support workforce development through the training and education of a graduate student at the University of Colorado.