The SnowEx Campaign - Testing new approaches for mapping snow water equivalent in forested regions and other areas
Organizing Team Leads: Edward Kim, Charles Gatebe, Amy Misakonis & Kelly Elder
Other Team Leads/Members: Ludovic Brucker, Christopher Crawford, Jeffrey Deems, Eugenia De Marco, Chris Derksen, Dorothy Hall, Chris Hiemstra, D. K. Kang, Alex Langlois, Amanda Leon, Glen Liston, Jessica Lundquist, HP Marshall, Noah Molotch, Anne Nolin, Thomas Painter, and many others
Sponsor: NASA HQ/Terrestrial Hydrology Program, Jared Entin
What is SnowEx?
SnowEx is a multi-year airborne snow campaign.
The overarching question that SnowEx will address is: How much water is stored in Earth’s terrestrial snow-covered regions? We will investigate the distribution of snow-water equivalent (SWE) and the snow energy balance in different canopy types and densities and terrain. We will use a unique combination of sensors, including LiDAR, active and passive microwave, an imaging spectrometer and infrared sensors to determine the sensitivity and accuracy of different remote sensing techniques for measurement of SWE. Ground-based instruments, snow field measurements and modeling will all also be required to help address the science questions.
A large fraction of snow-covered lands are forested, however most remote sensing techniques have found forested areas challenging. But recent developments, like LiDAR, have opened up new possibilities. And even passive microwave has shown to have more promise in forested areas than previously thought. Since the SnowEx research community wants to fully understand the various techniques, focusing on the challenges presented by forests is the perfect opportunity to collect a unique dataset that will help address the science questions and enable snow mission design trade studies, which would otherwise be hard to justify.
SnowEx is a little different than the typical science-only field campaign—and that’s part of what makes it exciting!
SnowEx/year-1 Science Traceability Matrix (STM) is now available online.
How is SnowEx organized?
NASA HQ has directed the SnowEx organizing team, led by NASA Goddard, in collaboration with the International Snow Remote Sensing Working Group (iSWGR) leadership, to organize the snow remote sensing community and execute the Year 1 field campaign.
A kickoff SnowEx workshop was held in July 2015 in Columbia, MD. A second SnowEx workshop was held in Seattle, Washington, in March of 2016. Following these workshops, the organizing team has been hard at work collecting information on sites, sensors, and aircraft, for the community to study and discuss.
When is SnowEx?
“Winter 1” activities will take place from February 6-24, 2017. A small subset of sensors—LiDAR and radar--require background measurements without snow before this time period (late September 2016). The full suite of sensors will fly in February 2017 to collect multi-sensor observations in dry snow conditions.
The focus of Year 2 (FY18) will be analysis of Year 1 data and planning of future activities. Minor targeted additional observations might be undertaken to fill critical gaps needed for analysis.
Further airborne and ground data collection would continue in 2019-2021. See the recent call for proposals from the NASA Terrestrial Hydrology Program at nspires.nasaprs.com
Where will SnowEx be Undertaken?
In Year 1, the SnowEx field and aircraft campaign will take place in Grand Mesa, Colorado, with a secondary site located at Senator Beck, Colorado. Site selection for all years was and will be based on the site characteristics needed to achieve SnowEx objectives. At the 2015 Columbia, MD SnowEx workshop, we collected community input on desirable SnowEx site characteristics, and since then we have collected information on specific sites themselves. Use this website to look at the current list of characteristics and descriptions of candidate sites. These lists are not complete—we depend on you to help make sure all potential sites are thoroughly characterized so a fair and transparent selection can be conducted. Send site-related info to Chris Crawford, so it can be posted on this SnowEx website for all in the community to study. For cost reasons, the sites for Winter 1 will be in the North America, but observations outside that area have not been ruled out for future years.
“Forest” in the SnowEx context refers to the whole continuum from “no trees” up to thick forests that block all remote sensing techniques. In order to determine at what point a sensing technique stops working in increasingly dense forests, we plan to observe an area that has a gradient of the confounding factor (e.g., from no trees up to a fully-closed forest canopy), and the gradient should be free of additional varying factors (e.g., complex topography, mixed-pixel effects, etc). Successful algorithms developed for forested areas via SnowEx could change vast areas of the Earth from having no snow retrievals to having some retrievals.
Why use forest as the confounding factor to challenge the sensing techniques; why not use complex topography?
Both forest and complex topography are challenges to snow remote sensing. There are multiple reasons to choose forest for SnowEx.
Three of four recent snow mission proposals have been rejected in significant part because snow retrieval in forested areas was not adequately addressed. If we want a future mission proposal to succeed, we simply have to address forests, or the proposal will be “dead on arrival.”
To determine at what point a sensing technique stops working, we would ideally observe an area that has a gradient of the confounding factor (e.g., from no trees up to a fully closed forest canopy), and the gradient should be free of additional varying factors (e.g., complex topography, mixed-pixel effects, etc). We feel it will be easier to achieve clearer conclusions by using forest. Also, any successful algorithms developed for forested areas via SnowEx could change vast areas of the Earth from having no snow retrievals to having something.
Why do we need SnowEx?
Specifically, we will conduct field experiments with the following objectives:
- Quantify SWE in open and forested areas for different canopy densities and terrain.
- Quantify snow albedo in open and forested areas for different canopy densities and snow conditions.
The result will be a major leap forward in our ability to estimate global SWE and toward defining a new snow space mission concept.
If you are interested in the future of snow remote sensing, we encourage you to join the SnowEx effort. Help us to design and execute SnowEx--to work towards a future snow satellite mission while also enabling critical, innovative, ground-breaking science at the same time. If you’d like to be added to the SnowEx email list, please contact Charles Gatebe.
** Please note that the content here is subject to change as it is still a work in progress.