Gunn, Grant E; Duguay, Claude R; Derksen, Chris; Lemmetyinen, Juha; Toose, Peter (2011): (Table 3) Air temperatures, and snow and ice characteristics of fresh and brackish water lakes in the Northwest Territories, Canada [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.810343, Supplement to: Gunn, GE et al. (2011): Evaluation of the HUT modified snow emission model over lake ice using airborne passive microwave measurements. Remote Sensing of Environment, 115(1), 233-244, https://doi.org/10.1016/j.rse.2010.09.001
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Abstract:
The algorithms designed to estimate snow water equivalent (SWE) using passive microwave measurements falter in lake-rich high-latitude environments due to the emission properties of ice covered lakes on low frequency measurements. Microwave emission models have been used to simulate brightness temperatures (Tbs) for snowpack characteristics in terrestrial environments but cannot be applied to snow on lakes because of the differing subsurface emissivities and scattering matrices present in ice. This paper examines the performance of a modified version of the Helsinki University of Technology (HUT) snow emission model that incorporates microwave emission from lake ice and sub-ice water. Inputs to the HUT model include measurements collected over brackish and freshwater lakes north of Inuvik, Northwest Territories, Canada in April 2008, consisting of snowpack (depth, density, and snow water equivalent) and lake ice (thickness and ice type). Coincident airborne radiometer measurements at a resolution of 80x100 m were used as ground-truth to evaluate the simulations.
The results indicate that subsurface media are simulated best when utilizing a modeled effective grain size and a 1 mm RMS surface roughness at the ice/water interface compared to using measured grain size and a flat Fresnel reflective surface as input. Simulations at 37 GHz (vertical polarization) produce the best results compared to airborne Tbs, with a Root Mean Square Error (RMSE) of 6.2 K and 7.9 K, as well as Mean Bias Errors (MBEs) of -8.4 K and -8.8 K for brackish and freshwater sites respectively. Freshwater simulations at 6.9 and 19 GHz H exhibited low RMSE (10.53 and 6.15 K respectively) and MBE (-5.37 and 8.36 K respectively) but did not accurately simulate Tb variability (R= -0.15 and 0.01 respectively). Over brackish water, 6.9 GHz simulations had poor agreement with airborne Tbs, while 19 GHz V exhibited a low RMSE (6.15 K), MBE (-4.52 K) and improved relative agreement to airborne measurements (R = 0.47). Salinity considerations reduced 6.9 GHz errors substantially, with a drop in RMSE from 51.48 K and 57.18 K for H and V polarizations respectively, to 26.2 K and 31.6 K, although Tb variability was not well simulated. With best results at 37 GHz, HUT simulations exhibit the potential to track Tb evolution, and therefore SWE through the winter season.
Project(s):
Coverage:
Median Latitude: 68.804250 * Median Longitude: -133.344500 * South-bound Latitude: 68.536000 * West-bound Longitude: -133.800000 * North-bound Latitude: 69.000000 * East-bound Longitude: -132.726000
Date/Time Start: 2008-04-06T00:00:00 * Date/Time End: 2008-04-06T00:00:00
Minimum Elevation: 2.0 m * Maximum Elevation: 33.0 m
Event(s):
Lake_Noel (Parsons Lake) * Latitude: 68.948000 * Longitude: -133.630000 * Date/Time: 2008-04-10T00:00:00 * Elevation: 33.0 m * Location: Northwest Territories, Canada * Method/Device: Snow/ice sample (SNOW)
Comment:
Note that the exact position of Lakes A and B could not be derived from the article. Data extracted in the frame of a joint ICSTI/PANGAEA IPY effort, see http://doi.pangaea.de/10.1594/PANGAEA.150150
Parameter(s):
| # | Name | Short Name | Unit | Principal Investigator | Method/Device | Comment |
|---|---|---|---|---|---|---|
| 1 | Event label | Event | ||||
| 2 | Latitude of event | Latitude | ||||
| 3 | Longitude of event | Longitude | ||||
| 4 | Water bodies | Water bodies | Gunn, Grant E | |||
| 5 | Site | Site | Gunn, Grant E | |||
| 6 | DATE/TIME | Date/Time | Geocode | |||
| 7 | Date/time end | Date/time end | Gunn, Grant E | |||
| 8 | Temperature, air | TTT | °C | Gunn, Grant E | ||
| 9 | Snow thickness | Snow thick | m | Gunn, Grant E | ||
| 10 | Snow water equivalent | SWE | mm | Gunn, Grant E | ||
| 11 | Density, snow | Density snow | kg/m3 | Gunn, Grant E | ||
| 12 | Snow grain size | Snow grain size | mm | Gunn, Grant E | ||
| 13 | Sea ice thickness | EsEs | m | Gunn, Grant E | lake ice | |
| 14 | Ice type | Ice type | Gunn, Grant E |
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
250 data points