SAIL

Surface Atmosphere Integrated Field Laboratory (SAIL)

1 September 2021 - 15 June 2023

Lead Scientist: Daniel Feldman

Observatory: AMF , GUC

Mountains are the natural water towers of the world, but Earth System Models (ESMs) have persistently been unable to predict the timing and availability of water resources from mountains. The source(s) of model error are difficult to isolate in complex terrain with limited atmospheric or land-surface observations. Further complications arise from the gross scale mismatch between ESM grid box sizes and the relevant scales of mountainous hydrological processes. The mountain hydrometeorology community has repeatedly called for integrated atmospheric and surface observations of water and energy budgets in complex terrain that span these scales to establish benchmarks against which scale-dependent models can be developed. In response to these calls, the Surface Atmosphere Integrated Field Laboratory (SAIL) will make measurements using the second ARM Mobile Facility (AMF2) and a scanning X-band dual polarimetric radar near Crested Butte, Colorado. The campaign will focus on the East River Watershed, which is a 300-km2 mountainous watershed that is part of the Upper Colorado River Basin. SAIL will advance atmosphere-through-bedrock understanding of mountainous water cycles by collocating ARM atmospheric observations with long-standing collaborative resources including the ongoing surface and subsurface hydrologic observations from the Department of Energy’s Watershed Function Science Focus Area (SFA). The main science goal of the SAIL campaign is to develop a quantitative understanding of the atmosphere and land-atmosphere interaction processes, at their relevant scales, that impact mountain hydrology in the midlatitude continental interior of the United States.

To achieve this goal, the campaign will extend from September 2021 to June 2023, and will measure the seasonally varying controls on the surface energy and water budgets in high-altitude complex terrain in order to address four key science questions:

1. How do multi-scale dynamic and microphysical processes control the spatial and temporal distribution, phase, amount, and intensity of precipitation?

2. How strongly do aerosols affect the surface energy and water balance by altering clouds, precipitation, and surface albedo, and how do these impacts vary seasonally?

3. What are the contributions of snow sublimation, radiation, and turbulent fluxes of latent and sensible heat to the water and energy balance of the snowpack?

4. How do atmospheric and surface processes set the net radiative absorption that is known to drive the regional flow of water into the continental interior during the summer monsoon?

To answer these questions, SAIL measurements will pursue the following science objectives:

1. Characterize the spatial distribution of orographic and convective precipitation processes on diurnal to seasonal time scales and how those processes interact with large-scale circulation.

2. Quantify cold-season land-atmosphere interactions that alter snowpack mass balance through wind redistribution and sublimation and the spatial scaling of those processes.

3. Establish aerosol regimes, the processes controlling the life cycle of aerosols in those regimes, and quantify the impacts of aerosols in those regimes on the atmospheric and surface radiative budget.

4. Quantify the sensitivity of cloud phase and precipitation to cloud condensation nuclei (CCN) and ice-nucleating particle (INP) concentrations.

5. Quantify the seasonally varying surface energy balance, the land-surface and atmospheric factors controlling it, and the spatial variability in those factors.

By measuring the inputs to, outputs from, and processes within a heavily studied mountainous watershed, SAIL will produce a benchmark data set for atmospheric and surface process representation studies. Those studies, in turn, will be used to develop a robust foundation for advancing the sub-grid representation of these processes in ESMs.

SAIL is complemented by a concurrent NOAA-led campaign in the region: the Study of Precipitation, the Lower Atmosphere, and Surface for Hydrometeorology (SPLASH). The yearlong SPLASH campaign is designed to gain detailed insight into the physical processes that drive basin-scale weather and water availability in the Mountain West. SPLASH will run through summer 2022.