Breakout Summary Report

ARM/ASR User and PI Meeting

Session Title: Advancing Atmospheric Process Studies in High-Altitude Complex Terrain with the Surface Atmosphere I
Session Date: 25 June 2020
Session Time: 11:00 AM - 1:00 PM
Number of Attendees: 145
Summary Authors: Daniel Feldman, Scott Collis

Breakout Description

This breakout session will present an overview of the upcoming Surface Atmosphere
Integrated field Laboratory (SAIL) campaign and its science questions and objectives. The campaign
includes the use of the AMF2 facilities and a precipitation radar to make intensive atmospheric and surface
measurements in the Rocky Mountains from 2021-2023 in southwestern Colorado near the town of
Crested Butte. Speakers will discuss science opportunities in high-altitude complex terrain, the types of
observations that are needed to advance these opportunities, and how specifically the observations will be
used to characterize precipitation processes, aerosol-precipitation interactions, aerosol processes, surfaceatmosphere
interaction processes, and radiation. We will schedule significant time for questions and
discussion. There are several goals for this session including:
1. To introduce the ARM/ASR community to the SAIL campaign and its science questions and objectives.
2. To provide a survey of ongoing and upcoming fieldwork that is external to SAIL but will occur in and
around Crested Butte and which can complement the SAIL.
3. To solicit feedback from the ARM/ASR community regarding researchers’ data product needs and
atmospheric process studies that those data products can enable.
4. To discuss the opportunities to study spatial heterogeneity in complex terrain in order to ensure that
observations are scientifically relevant beyond the range of the observations.

Main Discussion

The purpose of the breakout session was to introduce the SAIL campaign to the ARM/ASR PI meeting community. Given that the announcement of the selection of the campaign in March, 2020 coincided with many changes to researchers’ work environments associated with COVID-19, this session was timely and the virtual format enabled attendance not just of the ARM/ASR PI meeting community, but also of researchers that will partner with SAIL.
The breakout session spanned two hours and had a number of science overview presentations. First, the campaign PI provided a high-level introduction to SAIL, the team, its science objectives and its current status. Second, Prof. Venkatachalam Chandrasekar, of Colorado State University, presented on behalf of the SAIL precipitation process sub-group, which consists of himself, Scott Collis of Argonne National Laboratory, Jiwen Fan of Pacific Northwest National Laboratory, Matt Kumjian and Jerry Harrington of Pennsylvania State University, Alan Rhoades of Lawrence Berkeley National Laboratory, and Adam Varble of Pacific Northwest National Laboratory, and he gave an overview of the precipitation process studies that SAIL can enable, first by showing the value of X-band dual-polarimetric scanning Doppler radar data for measuring the amount and phase of precipitation, and then by showing how this spatial precipitation information directly maps onto microphysical precipitation processes to enable process studies.
Third, Allison Aiken, of Los Alamos National Laboratory, presented on behalf of the SAIL aerosol process sub-group, which consists of herself, Paul DeMott of Colorado State University, Jiwen Fan, McKenzie Skiles of the University of Utah, and Jim Smith of University of California-Irvine. It should be noted that Jessie Creamean of Colorado State University has joined this group since this breakout session. Dr. Aiken presented on how the observations of aerosols can enable key aerosol process studies. She discussed how SAIL observations will characterize the lifecycle of aerosols in the Colorado River Watershed. She also indicated that these observations will help characterize the radiative effects of these aerosols in the atmosphere and at the surface as a function of differing aerosol regimes. She presented key science questions for characterizing aerosol lifecycles and regimes and discussed how novel ice-nucleating particles and surface observations of distributed aerosol deposition (e.g., from snowpits) can advance aerosol science with SAIL.
Fourth, Jiwen Fan, presented on aerosol-precipitation interactions, and that SAIL data can be used to understand how aerosols may suppress moderate precipitation while enhancing extreme precipitation. She presented on how the observations will characterize how new particle formation events control the variability in aerosol hygroscopicity and cloud condensation nuclei concentrations, how the observations will characterize the sources of ice-nucleating particles, and how aerosol regimes impact aerosol-precipitation interactions.
Fifth, Ryan Sullivan presented on land-atmosphere interaction science opportunities. He presented on how SAIL data can characterize the controls on wintertime latent and sensible heat fluxes, the role of snow sublimation on impacting the energy balance at the surface, the impact of aerosols on surface albedo and distributions of sensible and latent heat, how to characterize advective fluxes during springtime where there is a patchwork of frozen surfaces and unfrozen surfaces, and impacts of these surface fluxes on hydrology. Even though his connection dropped during the presentation, he was nevertheless able to touch on the key issues with surface fluxes in the mountain West, and he indicated that there is a possibility of an additional ECOR instrument for the SAIL campaign.
Finally, Dave Gochis of NCAR presented on integrated process modeling, and how observations from SAIL and the Watershed Function SFA can be used jointly to test models such as WRF-Hydro. He indicated key science questions that link atmosphere, surface, and sub-surface processes to watershed discharge, and involve the dominant energy controls and the roles of landscape complexity and vegetation on water budget partitioning. He also raised some larger contextual issues, such as the upcoming renegotiation of the Colorado River Drought Plan, and links with other agency efforts including USGS NGWOS and NOAA, since WRF-Hydro forms the backbone of the NOAA National Water Model.
After the presentations, the last 40 minutes of the breakout session was open to discussion with attendees. In this discussion, a number of points were raised.
First, there were a number of external partnership discussions: Dr. David Lesmes of the US Geological Survey mentioned that his program looks forward to utilizing SAIL data and working closely with the campaign, since it would be beneficial to the Next Generation Water Observing System (NGWOS) for the Upper Colorado River. Dr. Lesmes inquired about how the USGS can contribute to SAIL.
Second, Gijs de Boer indicated that he is pursuing a campaign that would be a companion to SAIL called SPLASH (Study of Precipitation and Lower-Atmospheric impacts on Streamflow and Hydrology) with the NOAA Physical Sciences Laboratory. SPLASH would potentially bring significant additional instrumentation and modeling, including S-band snow level and precipitation radars, an Unmanned Aerial System, flux towers, a wind profiler, and disdrometers, as well as additional work to evaluate and improve a variety of models including the National Water Model, the High-Resolution Regional Reanalysis (HRRR), and possibly collaborate with GFDL to assess their Earth System Modeling performance in the Rocky Mountains.
In addition to the partnership discussion, there were also questions about leveraging existing observational capabilities to advance SAIL’s science objectives. Dr. Margaret Torn of Lawrence Berkeley National Laboratory asked if sublimation processes could be constrained by seasonal snowpack observations from the Airborne Snow Observatory (ASO), and the SAIL PI responded that this will be a challenge, given that ASO measures a seasonal integration of a large number of processes that impact snow including precipitation, sublimation, redistribution, rain-on-snow, and melt.
Jerome Fast inquired about whether SAIL would include direct measurements of biological particles and dust, and Allison Aiken and McKenzie Skiles mentioned that dust would be measured, but there are not current mechanisms to measure biological particles, but indicated that a guest instrument proposal for such measurements would be warranted.
There was then discussion on siting needs between the SAIL PI, Dr. Ken Williams of the Watershed Function SFA, and Dr. Heath Powers of LANL, and how to plan for travel in the face of COVID restrictions.
Finally, Dr. Jeff Stehr provided a programmatic perspective of the SAIL campaign, indicating that the ASR program is very enthusiastic about the SAIL campaign, especially given its direct relevance to the 40 million people that rely on the Colorado River for water.

Key Findings

From the attendance, questions, and additional people who asked to join the SAIL mailing list after the breakout session, there was substantial interest both within the ARM/ASR PI Meeting community in the upcoming SAIL campaign, and that interest is matched by scientific interest outside of the ARM/ASR community in using these data to advance mountainous hydrology research in general and scientific challenges pertaining to water in the West, in particular.
There will be substantial opportunities to advance the SAIL campaign’s science objectives given the campaign’s duration of nearly two years, but far more discussions are needed, especially to coordinate science activities, establish points of contact for these activities, and identify data needs, including IOPs. A virtual workshop is an appropriate venue for these discussions.

Issues

The one issue that arose at the end of the breakout session pertained to a site survey to select locations that can best serve SAIL’s science objectives. This survey requires the SAIL PI, representation from the Watershed Function SFA, representation from FIDO, and representation from Prof. Venkatachalam Chandrasekar’s Lab at Colorado State University. Given the timeline of the SAIL campaign, this survey needs to take place in before October, 2020, but is facing COVID-19 travel restrictions.

Needs

N/A

Decisions

A virtual workshop will be planned and held in late summer/early fall 2020 to ensure that SAIL science activities are coordinated, points of contact for these activities are established, and data needs are identified.

Future Plans

The planning for the SAIL campaign is underway and is very active. The siting of the X-band radar, the AOS, and the remainder of the SAIL instruments is a prime consideration and will have significant implications for the scope of science that can be achieved with the campaign.
The SAIL PI will be in close collaborations with the SAIL science team regarding siting decisions.
The SAIL PI will also be scheduling a virtual workshop in late summer/early fall of 2020.

Action Items

The primary action-items include:
• Developing a short-list of candidate sites for SAIL instrumentation.
• Socializing the SAIL campaign with the larger scientific community.
• Planning and implementing a SAIL virtual workshop for late summer/early fall 2020.