TY - Generic T1 - Snowmelt Detection from Sentinel-1 Synthetic Aperture Radar in the Lajoie Basin, British Columbia T2 - 88th Annual Western Snow Conference Y1 - 2021 A1 - Sara Darychuk A1 - Joseph Shea A1 - Anna Chesnokova A1 - Brian Menounos A1 - Frank Weber A1 - Georg Jost KW - Google Earth Engine KW - remote sensing KW - snowmelt KW - snowpack dynamics KW - Synthetic Aperture Radar AB -

Snowmelt runoff supplements streamflow and soil moisture during warm summer months in Western North America. As direct snowpack measurements are sparse, many models exist to predict the release of runoff in alpine regions. An increase in spatially distributed observational data of seasonal snow may help to refine and improve these efforts going forward. Synthetic Aperture Radar (SAR) is sensitive to the liquid water content of snow and has been successfully used to map wet snow in alpine regions. We employ SAR and multispectral data to estimate the onset and duration of snowmelt in 2018 in the Lajoie Basin, British Columbia. We collate and process Sentinel-1, Sentinel-2 and Landsat-8 images in Google Earth Engine. A backscatter threshold is used to define the inferred period at which the snowpack is saturated and begins to generate runoff. Multispectral imagery is used to estimate snow-free dates across the basin to define the end of the snowmelt period. These methods are most effective on moderate to low slopes (< 30°) in open areas. This approach has high potential for adaptability to other alpine basins or regions and can be used for future model calibration.

JF - 88th Annual Western Snow Conference CY - Bozeman, MT UR - /files/PDFs/2021Darychuk.pdf ER - TY - Generic T1 - Review of the Past 20 Years of Hydroclimate Data in Yosemite National Park (Poster) T2 - 88th Annual Western Snow Conference Y1 - 2021 A1 - Rachel Hallnan A1 - Chad Anderson A1 - Catherine Fong KW - climate change KW - runoff KW - Sierra Nevada KW - snowmelt KW - Yosemite AB -

The impacts of climate change are projected to be profound in mountainous, snowpack dominated regions of the Sierra Nevada Mountains. Anticipated impacts include a shift in precipitation from snow to rain, increasing snow lines, higher air and stream temperatures, and shifting snowmelt and peak runoff timing earlier in the year. Such changes have implications on natural resources such as vegetation distribution, stream ecosystems and water quality, natural fire regime, wildlife abundance and diversity, and the quantity and distribution of water resources valued and stewarded by the National Park Service. Yosemite National Park, spanning elevations from 640 – 4000 m in the central Sierra Nevada Mountains is equipped with a robust network of snowpack, meteorological, and stream monitoring instrumentation, and provides a unique opportunity to examine water regime shifts over time. Data collection within the park is often a collaborative effort between park resource managers, researchers, and state agencies to satisfy multiple objectives. For park resource managers, these long-term datasets provide an opportunity to examine local weather and climate trends to better understand local climate change impacts and use this knowledge to inform resource management decisions. Presented here are long term trends in temperature and precipitation for the high elevations of the park, and trends in snowpack and streamflow timing over the past twenty years of hydroclimate monitoring within Yosemite.

JF - 88th Annual Western Snow Conference CY - Bozeman, MT UR - /files/PDFs/2021Hallnan.pdf ER - TY - Generic T1 - Variability of Cloud Cover and its Relation to Springtime Snowmelt and Runoff T2 - 83rd Annual Western Snow Conference Y1 - 2015 A1 - Edwin Sumargo A1 - Daniel R. Cayan KW - cloud variability KW - empirical orthogonal function KW - satellite remote sensing KW - snowmelt KW - streamflow AB -

Much of the variability in water supply and an important part of the uncertainty in water supply forecasts are driven by the variability in solar insolation, which in turn is modulated by cloud cover. Here we investigate the space/time variability of cloud and incoming radiation and how it may affect snowmelt and streamflow. We use NASA/NOAA Geostationary Operational Environmental Satellite (GOES 9-11 and 15) albedo product (α) spanning from 1996 to 2012 during the daytime (8-16 PST) over the westernmost U.S. (25-50 °N, 113-130 °W) with 4-km spatial and 30-minute temporal resolutions. Only elevations above 800 meters are included to avoid contaminations from coastal marine and low stratus clouds. A translation of cloud albedo (αcloud) to incoming surface radiation yields results that are well correlated with time series from surface radiometers at selected Sierra Nevada locations. Cloud albedo varies considerably from day to day, month to month, and even from year to year. To determine the most prominent spatial αcloud patterns and their temporal variability, we conduct a Rotated Empirical Orthogonal Function/Principal Component (REOF/PC) analysis. The 5 leading REOFs account for ~66% of the total αcloud variance. The leading REOF (~19%) covers portions of the Sierra Nevada and the Cascades and has a relatively high variance during the springtime, indicating its pertinence to snowmelt. During spring and early summer, these anomalous cloud patterns exhibit significant influence on snowmelt and runoff (R2 > 30%), with anomalously high αcloud producing lower snowmelt/runoff and vice versa. Correlations reveal a strong change in the response to incoming radiation of snowmelt and streamflow over the seasonal transition from winter-to-spring-to-summer. Dry years and wet years exhibit considerable difference in cloud amount and pattern, with lower overall springtime cloudiness in drier years, which leads to higher surface radiation available for snowmelt.

 

Presentation in PDF

JF - 83rd Annual Western Snow Conference T3 - Proceedings of the Western Snow Conference CY - Grass Valley, California UR - /files/PDFs/2015Sumargo.pdf ER - TY - Generic T1 - Soil Moisture Dynamics During Snowmelt T2 - 82nd Annual Western Snow Conference Y1 - 2014 A1 - Kent Sutcliffe KW - active melt KW - diurnal fluctuation KW - snow KW - snowmelt KW - soil moisture AB -

Little research exists examining soil moisture characteristics under a snowpack, especially during the active meltout period. Unlike snow water equivalent (SWE) and snow depth, which has been measured by the Snow Survey Program for 80 years, soil moisture changes during meltout have been difficult to monitor and analyze. Advances in sensor technology, increased deployment of instrumentation, and longer period of records present new opportunities for analysis and a better understanding of soil moisture dynamics under snowmelt. Three characteristic annual soil moisture patterns are discussed. Analysis of hourly soil moisture, SWE, and precipitation data have resulted in the observation of new relationships between daily snowmelt and soil moisture. At most SNOTEL sites, snowpack melt results in diurnal soil moisture fluctuations. At well-drained sites, during periods of rapid melt, fluctuations of up to 10 percent soil moisture by volume are observed. Typically, fluctuations are expressed by all three sensors through the 50 cm measurement zone during the entire meltout period, or until saturation is reached. Diurnal fluctuations in soil moisture scale in magnitude with the SWE loss during the same period. At sites with well-drained soils and no run-in from adjacent areas, the volume of water transmitted through the entire 50 cm zone correlates well with the volume of SWE loss on a daily basis. Four select sites with different soil properties and geographic areas within Utah and California are examined and the correlation between SWE and soil water flux is quantified and found to range from an R2 of 0.50 to 0.76. Analysis of diurnal soil moisture fluctuation provides a valuable window into the significant water flux occurring during the melt cycle and may assist in making soil moisture a quantitative input in statistical-based streamflow forecasting.

JF - 82nd Annual Western Snow Conference T3 - Proceedings of the Western Snow Conference CY - Durango, Colorado UR - sites/westernsnowconference.org/PDFs/2014Sutcliffe.pdf ER - TY - Generic T1 - Understanding the Spatial Distribution of Snow Water Equivalent and Subsequent Snowmelt Runoff Patterns of Paired Basins in Southwest Montana T2 - 82nd Annual Western Snow Conference Y1 - 2014 A1 - Jason Welz A1 - Jordy Hendrikx A1 - Stuart Challender A1 - Paul Stoy KW - avalanche KW - mountain hydrology KW - runoff KW - Snow water equivalent KW - snowmelt AB -

This paper presents the initial results of a research project with the primary goal of investigating the hydrologic role of avalanche activity alongside the physiographic variables (i.e. elevation, slope, aspect, wind shelter/exposure, landcover, and solar radiation) that the snow hydrology community widely consider to be the dominant controls on the spatial distribution of snow water equivalent (SWE) and subsequent snowmelt runoff in alpine basins. An extensive field campaign was conducted in two adjacent alpine basins in southwest Montana from January 31 to August 21, 2013, consisting of three survey periods to capture snowpack metrics during the phases of (1) accumulation; (2) peak SWE, and (3) ablation/snowmelt runoff. During each period, the same stratified random sampling methods were used to measure snow depth and SWE at transects along elevation contours. Transects were spatially distributed with the goal of acquiring a representative sample of the aforementioned physiographic variables as well as the components of avalanche paths. After quantifying the contribution of each of these variables to the distribution of SWE, we will also consider their impact on the timing and magnitude of snowmelt runoff. This will be determined by correlation to stream discharge measurements that were collected throughout the 2012- 2013 water year. The initial results are discussed as are the future steps.

JF - 82nd Annual Western Snow Conference T3 - Proceedings of the Western Snow Conference CY - Durango, Colorado UR - sites/westernsnowconference.org/PDFs/2014Welz.pdf ER - TY - Generic T1 - Estimating Snow Water Equivalent at NWS Climatological Stations T2 - 81st Annual Western Snow Conference Y1 - 2013 A1 - Farnes, Phillip KW - density KW - precipitation KW - Snow water equivalent KW - snowmelt KW - temperature AB -

Typically, National Weather Service (NWS) Climatological Stations measure snow depth but not snow water equivalent (SWE). However, SWE is generally more important than depth when used in hydrologic and wildlife studies. Typically, there are higher elevation stations that measure SWE but lower elevations stations are predominately Climatological stations that do not measure SWE. New snowfall densities are generally between 6 and 10 percent while snow packs can reach densities into the 25 to 35 percent range just prior to and during melt. As part of developing the climatic database for the core area of the Greater Yellowstone Area (GYA), daily SWE was computed for all Climatological Stations. Some of these stations have snow courses at or near the station. Also, snow measurements were made at some of these stations in conjunction with the Snow Sinking Studies on the Northern Range of Yellowstone National Park. Methods for computing daily SWE using snow depth, precipitation and temperature will be presented as well as comparisons between estimated SWE and measured SWE at ten stations. The lengths of records where both measured and estimated SWE exist vary from about 17 years up to about 75 years. Long range trends of SWE will be shown for stations with longer records.

JF - 81st Annual Western Snow Conference T3 - Proceedings of the Western Snow Conference CY - Jackson Hole, Wyoming UR - sites/westernsnowconference.org/PDFs/2013Farnes.pdf ER - TY - Generic T1 - What Makes Rain-on-Snow Events Hazardous: Field Study at Ward Valley, Lake Tahoe Basin T2 - 81st Annual Western Snow Conference Y1 - 2013 A1 - Ohara, N. A1 - Kavvas, M.L. A1 - Easton, D. A1 - Dogrul, E.C. A1 - Yoon, J.Y. A1 - Chen, Z.Q. KW - field measurement KW - overland flow KW - rain-on-snow event KW - snowmelt KW - spring flood AB -

Rain-on-snow events tend to be more hazardous than snow-free-rainfall-runoff or snowmelt events in Western States. The field observations in Ward Creek watershed, Tahoe Basin, showed that the snowmelt induced by energy flux from raindrops scarcely contributes to the hillslope runoff during the major rain-on-snow event of May 7, 2000, due to the cold weather. Spring high flows in the Sierra Nevada may be mainly due to the high soilwater content in the top soil kept by continuous snowmelt water supply. It was also found that the overland flow or longitudinal flow within the snowpack may still happen even over unfrozen and unsaturated topsoil on a relatively mild hillslope (16 %). The overland/in-snow flow may be due to the difference in hydraulic conductivities of the snow and the top-soil. This overland flow within the snowpack may form up to 10 percent of the peak flood discharge at the field hillslope scale. It may be hypothesized that the overland/in-snow flow on the unsaturated top soil may be a common phenomenon. The high flood peak of the rain-on-snow events may be magnified by this insnow fast runoff mechanism as well as the snowmelt by raindrop energy transfer. To test this observation-based hypothesis, further studies on the runoff process within the snowpack are desirable.

JF - 81st Annual Western Snow Conference T3 - Proceedings of the Western Snow Conference CY - Jackson Hole, Wyoming UR - sites/westernsnowconference.org/PDFs/2013Ohara.pdf ER - TY - Generic T1 - Lateral Free Water Flow and Snowmelt Lysimeters T2 - 81st Annual Western Snow Conference Y1 - 2013 A1 - Osterhuber, Randall KW - free water KW - lateral flow KW - lysimeter KW - snowmelt AB -

Five winters of snowpack free water outflow data from two 18 m2 snowmelt lysimeters at the UC Berkeley Central Sierra Snow Laboratory are analyzed against coincident measurements of precipitation, snow water equivalent accumulation and ablation, and snow depth. Challenges in using outflow data as a water balance tool are revealed by the sometime greatly differing amounts of outflow recorded by the side-by-side lysimeters, and the ratio of outflow to precipitation. The data here give insight to subsurface lateral free water flow. Also described is an attempt to inhibit lateral flow beyond the lysimeter’s borders by cutting the full profile of the melting spring snowpack.

JF - 81st Annual Western Snow Conference T3 - Proceedings of the Western Snow Conference CY - Jackson Hole, Wyoming UR - sites/westernsnowconference.org/PDFs/2013Osterhuber.pdf ER -