Center for Snow and Avalanche Studies

Silverton, CO, United States

Center for Snow and Avalanche Studies

Silverton, CO, United States
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News Article | February 16, 2017

Researchers have completed the first flights of a NASA-led field campaign that is targeting one of the biggest gaps in scientists' understanding of Earth's water resources: snow. NASA uses the vantage point of space to study all aspects of Earth as an interconnected system. But there remain significant obstacles to measuring accurately how much water is stored across the planet's snow-covered regions. The amount of water in snow plays a major role in water availability for drinking water, agriculture and hydropower. Enter SnowEx, a NASA-led multi-year research campaign to improve remote-sensing measurements of how much snow is on the ground at any given time and how much water is contained in that snow. SnowEx is sponsored by the Terrestrial Hydrology Program at NASA Headquarters in Washington, D.C., and managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland. The first year of the ground and air campaign takes place in February in western Colorado. "This is the most comprehensive campaign we have ever done on snow," said Edward Kim, a remote sensing scientist at NASA Goddard and the SnowEx project scientist. "An army of nearly 100 scientists from universities and agencies across the U.S., Europe and Canada are participating. Our goal is to find and refine the best snow-measuring techniques and how they could work together." Scientists know that they will need multiple sensors to measure the water content in snow. "No one instrument is perfect," said Charles Gatebe from NASA Goddard, SnowEx deputy project scientist and senior scientist with Universities Space Research Association. "One of our biggest problems is detecting snow through trees. We will work closely with our ground team to try new techniques to see if we can figure out how to do that accurately." More than one-sixth of the world's population relies on seasonal snow for water. In the western U.S., nearly three-quarters of the annual streamflow that provides the water supply arrives as spring and summer melt from the mountain snow packs. Right now, predictions of streamflow can vary widely due to limited ground measurement sites. This is one of the reasons scientists and resource managers are interested in a comprehensive view from space of what they call snow-water equivalent -- the amount of liquid water contained in snow cover. Scientists use snow-water equivalent to estimate the amount of water that will melt into mountain streams, rivers and reservoirs. Snow also effects and is affected by the climate. Scientists have detected changes in snow quantity and snowmelt timing that track with other changes prompted by Earth's warming climate. While satellites are not able to measure snow-water equivalent accurately over all snowy landscapes, satellites have monitored the extent of seasonal snow-covered areas for decades. Since 1967, Northern Hemisphere spring snow cover has declined by about 1 million square miles. Loss of snow cover results in Earth absorbing more sunlight, accelerating the planet's warming. In the air, on the ground The instruments and techniques developed in campaigns such as SnowEx could one day result in a snow-observing space mission. "We will also figure out a better way to optimize the use of existing satellites to make measurements," said Jared Entin, program manager of the Terrestrial Hydrology Program at NASA Headquarters. Five aircraft with a total of 10 different sensors are part of the SnowEx campaign. From an operations base at Peterson Air Force Base, Colorado Springs, SnowEx will deploy a P-3 Orion aircraft operated by the Scientific Development Squadron ONE (VXS-1), stationed at the Naval Air Station Patuxent River, Maryland. High-altitude NASA jets will fly from NASA's Johnson Space Center in Houston, and NASA's Armstrong Flight Research Center in Palmdale, California. A King Air and a Twin Otter will fly out of Grand Junction, Colorado. The planes will carry one passive and four active microwave sensors that are good at measuring snow-water equivalent in dry snow, but are less optimal for measuring snow in forests or light snow cover; a thermal infrared camera and a remote thermometer (KT-15) for measuring surface temperature; laser instrument that it good at measuring snow depth and snow water equivalent through trees; an imaging spectrometer which measures snow albedo -- the amount of sunlight reflected and absorbed by snow, which controls the speed of snowmelt and the timing of its runoff. The King Air carries the Airborne Snow Observatory from NASA's Jet Propulsion Laboratory in Pasadena, California. ASO is the first remote sensing system to ever measure snow depth, snow water equivalent and snow albedo across entire mountain basins, and has uniquely quantified snow water equivalent over mountainous regions since 2013. The field portion of the campaign is based in Grand Mesa and Senator Beck Basin. Scientists will use measurement and sampling procedures that will allow the team to validate the remotely-sensed measurements acquired by the multiple sensors on the various aircraft. Traditional and high-tech equipment is being used for the ground campaign, including snow pits and remote sensing instruments hoisted 40 feet in the air on boom trucks. "The big challenge to the ground campaign is collecting high-quality field measurements while keeping everyone safe and healthy in these harsh environments," said Kelly Elder, research hydrologist with the U.S. Forest Service's Rocky Mountain Research Station, Fort Collins, Colorado, who is leading the overall ground campaign. Scientists will be working above 10,000 feet in potentially windy and freezing conditions up to 10 hours a day. They need snow goggles or sunglasses to protect their eyes. Hypothermia is a very real threat, so researchers wear special clothing designed to wick away sweat and keep them dry. The teams use snowshoes, skis and snowmobiles to access the ground measurement locations on Grand Mesa and Senator Beck Basin. The Senator Beck Research Basin study area is near the headwaters of the Rio Grande River Basin. "Its research areas are the first major mountain systems downwind of the desert Southwest and Colorado Plateau, making it an ideal place to study the effects of dust on snowmelt," said Hans-Peter Marshall, of Boise State University, who is leading ground operations in Senator Beck Research Basin. "Grand Mesa was chosen for its flatness and range of forest conditions," said Chris Hiemstra, a research physicist with the U.S. Army Corps of Engineers, and the lead for the Grand Mesa ground operations. The variety of terrain and environments make the ground sites good models for developing global measurements of snow. Ground equipment was installed in September 2016, before snow started to fall. A ground site near a campground will host specialized equipment too large to move around. This Local Scale Observation Site effort is led by Ludovic Brucker from NASA Goddard. Teams of 50 researchers are making ground measurements, rotating in and out of the field every week over a three-week period. Data acquired from the SnowEx campaign will be stored at the National Snow and Ice Data Center in Boulder, Colorado, and will be available to anyone at no cost, as is the case with all NASA data. After the field work, SnowEx scientists will analyze data and recommend to NASA how to proceed in the next few years. "This campaign will generate the best ideas from the global community of snow experts," Kim said. Senator Beck Basin is managed by the Center for Snow and Avalanche Studies CSAS, a non-profit organization that hosts research studies on snowpack at the basin.

Lapo K.E.,University of Washington | Hinkelman L.M.,University of Washington | Landry C.C.,Center for Snow and Avalanche Studies | Massmann A.K.,University at Albany | Lundquist J.D.,University of Washington
Water Resources Research | Year: 2015

Downwelling solar, Qsi, and longwave, Qli, irradiances at the earth's surface are the primary energy inputs for many hydrologic processes, and uncertainties in measurements of these two terms confound evaluations of estimated irradiances and negatively impact hydrologic modeling. Observations of Qsi and Qli in cold environments are subject to conditions that create additional uncertainties not encountered in other climates, specifically the accumulation of snow on uplooking radiometers. To address this issue, we present an automated method for estimating these periods of snow accumulation. Our method is based on forest interception of snow and uses common meteorological observations. In this algorithm, snow accumulation must exceed a threshold to obscure the sensor and is only removed through scouring by wind or melting. The algorithm is evaluated at two sites representing different mountain climates: (1) Snoqualmie Pass, Washington (maritime) and (2) the Senator Beck Basin Study Area, Colorado (continental). The algorithm agrees well with time-lapse camera observations at the Washington site and with multiple measurements at the Colorado site, with 70-80% of observed snow accumulation events correctly identified. We suggest using the method for quality controlling irradiance observations in snow-dominated climates where regular, daily maintenance is not possible. © 2015. American Geophysical Union. All Rights Reserved.

Skiles S.M.,University of California at Los Angeles | Painter T.H.,University of California at Los Angeles | Painter T.H.,Jet Propulsion Laboratory | Deems J.S.,National Snow and Ice Data Center | And 3 more authors.
Water Resources Research | Year: 2012

Here we present the radiative and snowmelt impacts of dust deposition to snow cover using a 6-year energy balance record (2005-2010) at alpine and subalpine micrometeorological towers in the Senator Beck Basin Study Area (SBBSA) in southwestern Colorado, USA. These results follow from the measurements described in part I. We simulate the evolution of snow water equivalent at each station under scenarios of observed and dust-free conditions, and +2°C and +4°C melt-season temperature perturbations to these scenarios. Over the 6 years of record, daily mean dust radiative forcing ranged from 0 to 214 W m-2, with hourly peaks up to 409 W m-2. Mean springtime dust radiative forcings across the period ranged from 31 to 49 W m-2 at the alpine site and 45 to 75 W m-2 at the subalpine site, in turn shortening snow cover duration by 21 to 51 days. The dust-advanced loss of snow cover (days) is linearly related to total dust concentration at the end of snow cover, despite temporal variability in dust exposure and solar irradiance. Under clean snow conditions, the temperature increases shorten snow cover by 5-18 days, whereas in the presence of dust they only shorten snow duration by 0-6 days. Dust radiative forcing also causes faster and earlier peak snowmelt outflow with daily mean snowpack outflow doubling under the heaviest dust conditions. On average, snow cover at the towers is lost 2.5 days after peak outflow in dusty conditions, and 1-2 weeks after peak outflow in clean conditions. © 2012. American Geophysical Union. All Rights Reserved.

Painter T.H.,Jet Propulsion Laboratory | Painter T.H.,University of California at Los Angeles | Skiles S.M.,University of California at Los Angeles | Deems J.S.,National Snow and Ice Data Center | And 3 more authors.
Water Resources Research | Year: 2012

Dust in snow accelerates snowmelt through its direct reduction of snow albedo and its further indirect reduction of albedo by accelerating the growth of snow grains. Since the westward expansion of the United States that began in the mid-19th century, the mountain snow cover of the Colorado River Basin has been subject to five-fold greater dust loading, largely from the Colorado Plateau and Great Basin. Radiative forcing of snowmelt by dust is not captured by conventional micrometeorological measurements, and must be monitored by a more comprehensive suite of radiation instruments. Here we present a 6 year record of energy balance and detailed radiation measurements in the Senator Beck Basin Study Area, San Juan Mountains, Colorado, USA. Data include broadband irradiance, filtered irradiance, broadband reflected flux, filtered reflected flux, broadband and visible albedo, longwave irradiance, wind speed, relative humidity, and air temperatures. The gradient of the snow surface is monitored weekly and used to correct albedo measurements for geometric effects. The snow is sampled weekly for dust concentrations in plots immediately adjacent to each tower over the melt season. Broadband albedo in the last weeks of snow cover ranged from 0.33 to 0.55 across the 6 years and two sites. Total end of year dust concentration in the top 3 cm of the snow column ranged from 0.23 mg g1 to 4.16 mg g1. These measurements enable monitoring and modeling of dust and climate-driven snowmelt forcings in the Upper Colorado River Basin. © 2012. American Geophysical Union. All Rights Reserved.

Naud C.M.,Columbia University | Miller J.R.,Rutgers University | Landry C.,Center for Snow and Avalanche Studies
Journal of Geophysical Research: Atmospheres | Year: 2012

Many studies suggest that high-elevation regions may be among the most sensitive to future climate change. However, in situ observations in these often remote locations are too sparse to determine the feedbacks responsible for enhanced warming rates. One of these feedbacks is associated with the sensitivity of longwave downward radiation (LDR) to changes in water vapor, with the sensitivity being particularly large in many high-elevation regions where the average water vapor is often low. We show that satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earths Radiant Energy System (CERES) can be used to expand the current ground-based observational database and that the monthly averaged clear-sky satellite estimates of humidity and LDR are in good agreement with the well-instrumented Center for Snow and Avalanche Studies ground-based site in the southwestern Colorado Rocky Mountains. The relationship between MODIS-retrieved precipitable water vapor and surface specific humidity across the contiguous United States was found to be similar to that previously found for the Alps. More important, we show that satellites capture the nonlinear relationship between LDR and water vapor and confirm that LDR is especially sensitive to changes in water vapor at high elevations in several midlatitude mountain ranges. Because the global population depends on adequate fresh water, much of which has its source in high mountains, it is critically important to understand how climate will change there. We demonstrate that satellites can be used to investigate these feedbacks in high-elevation regions where the coverage of surface-based observations is insufficient to do so. Copyright 2012 by the American Geophysical Union.

Chen Y.,Columbia University | Naud C.M.,Columbia University | Rangwala I.,University of Colorado at Boulder | Rangwala I.,National Oceanic and Atmospheric Administration | And 2 more authors.
Environmental Research Letters | Year: 2014

Among the potential reasons for enhanced warming rates in many high elevation regions is the nonlinear relationship between surface downward longwave radiation (DLR) and specific humidity (q). In this study we use ground-based observations at two neighboring high elevation sites in Southwestern Colorado that have different local topography and are 1.3 km apart horizontally and 348 m vertically. We examine the spatial consistency of the sensitivities (partial derivatives) of DLR with respect to changes in q, and the sensitivities are obtained from the Jacobian matrix of a neural network analysis. Although the relationship between DLR and q is the same at both sites, the sensitivities are higher when q is smaller, which occurs more frequently at the higher elevation site. There is a distinct hourly distribution in the sensitivities at both sites especially for high sensitivity cases, although the range is greater at the lower elevation site. The hourly distribution of the sensitivities relates to that of q. Under clear skies during daytime, q is similar between the two sites, however under cloudy skies or at night, it is not. This means that the DLR-q sensitivities are similar at the two sites during daytime but not at night, and care must be exercised when using data from one site to infer the impact of water vapor feedbacks at another site, particularly at night. Our analysis suggests that care should be exercised when using the lapse rate adjustment to infill high frequency data in a complex topographical region, particularly when one of the stations is subject to cold air pooling as found here. © 2014 IOP Publishing Ltd.

Raleigh M.S.,U.S. National Center for Atmospheric Research | Landry C.C.,Center for Snow and Avalanche Studies | Hayashi M.,University of Calgary | Quinton W.L.,Wilfrid Laurier University | Lundquist J.D.,University of Washington
Water Resources Research | Year: 2013

Snow surface temperature (Ts) is important to the snowmelt energy balance and landatmosphere interactions, but in situ measurements are rare, thus limiting evaluation of remote sensing data sets and distributed models. Here we test simple Ts approximations with standard height (2-4 m) air temperature (Ta), wet-bulb temperature (Tw), and dew point temperature (Td), which are more readily available than Ts. We used hourly measurements from seven sites to understand which Ts approximation is most robust and how Ts representation varies with climate, time of day, and atmospheric conditions (stability and radiation). Td approximated Ts with the lowest overall bias, ranging from 22.3 to 12.6°C across sites and from 22.8 to 1.5°C across the diurnal cycle. Prior studies have approximated Ts with Ta, which was the least robust predictor of Ts at all sites. Approximation of Ts with Td was most reliable at night, at sites with infrequent clear sky conditions, and at windier sites (i.e., more frequent turbulent instability). We illustrate how mean daily T d can help detect surface energy balance bias in a physically based snowmelt model. The results imply that spatial Td data sets may be useful for evaluating snow models and remote sensing products in data sparse regions, such as alpine, cold prairie, or Arctic regions. To realize this potential, more routine observations of humidity are needed. Improved understanding of Td variations will advance understanding of T s in space and time, providing a simple yet robust measure of snow surface feedback to the atmosphere. © 2013. American Geophysical Union. All Rights Reserved.

Landry C.C.,Center for Snow and Avalanche Studies | Buck K.A.,Center for Snow and Avalanche Studies | Raleigh M.S.,U.S. National Center for Atmospheric Research | Clark M.P.,U.S. National Center for Atmospheric Research
Water Resources Research | Year: 2014

A hydrologic modeling data set is presented for water years 2006 through 2012 from the Senator Beck Basin (SBB) study area. SBB is a high altitude, 291 ha catchment in southwest Colorado exhibiting a continental, radiation-driven, alpine snow climate. Elevations range from 3362 m at the SBB pour point to 4118 m. Two study plots provide hourly forcing data including precipitation, wind speed, air temperature and humidity, global solar radiation, downwelling thermal radiation, and pressure. Validation data include snow depth, reflected solar radiation, snow surface infrared temperature, soil moisture, temperatures and heat flux, and stream discharge. Snow water equivalence and other snowpack properties are captured in snowpack profiles. An example of snow cover model testing using SBB data is discussed. Serially complete data sets are published including both measured data as well as alternative, corrected data and, in conjunction with validation data, expand the physiographic scope of published mountain system hydrologic data sets in support of advancements in snow hydrology modeling and understanding. Key Points Hydrologic modeling data set from high-elevation, snow-dominated catchment Hydrologic data set reflects enhanced radiative forcings of snowpack processes Senator Beck Basin is representative of many Colorado River tributary headwaters © 2014. American Geophysical Union. All Rights Reserved.

Axson J.L.,University of Michigan | Shen H.,University of Michigan | Bondy A.L.,University of Michigan | Landry C.C.,Center for Snow and Avalanche Studies | And 4 more authors.
Aerosol and Air Quality Research | Year: 2016

Transported mineral dust deposition to remote mountain snow decreases snow albedo and increases absorption of solar radiation, which accelerates snowpack melt and alters water supply. Mineralogy and chemical composition determine dust particle optical properties, which vary by source region. While impacts of dust deposition at remote mountain sites have been established, few studies have connected the chemical composition of ambient particles during deposition events with the properties of those deposited on the snowpack. Ambient particles and surface snow were sampled in the San Juan Mountains of southwestern Colorado, which frequently experiences dust deposition in the spring and has evidence of dust- enhanced snow melt. Individual particles were analyzed using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The number concentration and size distribution of insoluble residues in the top level of snow were determined with nanoparticle tracking analysis (NTA). During a minor dust event (April 2-3, 2015), the fraction of absorbing iron-enriched dust in the ambient aerosol, the number concentration, and size of insoluble residues in snow all increased. This can be traced to shifts in mineral dust source region within the Colorado Plateau, during which, there were higher wind speeds leading to increased transport. The shift in chemical composition and mineralogy of the transported dust has the potential to impact snowpack radiative forcing during dry deposition. In addition, it can also modify the snowpack through scavenging of particles during wet deposition, as well as alter the properties of clouds and orographic precipitation. Understanding these impacts is crucial to understanding the hydrological cycle at remote mountain sites. © Taiwan Association for Aerosol Research.

Lawrence C.R.,University of Colorado at Boulder | Painter T.H.,University of Colorado at Boulder | Painter T.H.,Jet Propulsion Laboratory | Landry C.C.,Center for Snow and Avalanche Studies | Neff J.C.,University of Colorado at Boulder
Journal of Geophysical Research: Biogeosciences | Year: 2010

Dust deposition in the Rocky Mountains may be an important biogeochemical flux from upwind ecosystems. Seasonal (winter/spring) dust mass fluxes to the San Juan Mountains during the period from 2004 to 2008 ranged from 5 to 10 g m-2, with individual deposition events reaching as high as 2 g m -2. Dust deposited in the San Juan Mountains was primarily composed of silt- and clay-sized particles, indicating a regional source area. The concentrations of most major and minor elements in this dust were similar to or less than average upper continental crustal concentrations, whereas trace element concentrations were often enriched. In particular, dust collected from the San Juan Mountain snowpack was characterized by enrichments of heavy metals including As, Cu, Cd, Mo, Pb, and Zn. The mineral composition of dust partially explained dust geochemistry; however, based on results of a sequential leaching procedure it appeared that trace element enrichments were associated with the organic-, and not the mineral-, fraction of dust. Our observations show that the dust-derived fluxes of several nutrients and trace metals are substantial and, because many elements are deposited in a mobile form, could be important controls of vegetation, soil, or surface water chemistry. The flux measurements reported here are useful benchmarks for the characterization of ecosystem biogeochemical cycling in the Rocky Mountains. Copyright 2010 by the American Geophysical Union.

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