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|Title:||On the thermal nature and sensing of snow-covered Arctic terrain|
|Authors:||Poulin, Ambrose O.|
|Publisher:||U.S. Army Engineer Topographic Laboratories.|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Research note (U.S. Army Engineer Topographic Laboratories) ; ETL-RN-73-4.|
Abstract: Thermal infrared imagery (8 to 14 micrometers) of selected areas of the North American Arctic above the 75th parallel was obtained at three different periods: early winter, midwinter and early spring. Data runs totaling approximately 2500 nautical miles in length were made at altitudes ranging from 1000 to 20,000 feet. Environmental conditions included: ( 1) daytime with solar altitudes from 2 to 27 degrees and the atmosphere ranging from very clear to very hazy, and (2) very clear to very hazy conditions during the dark season. Subjects covered included sea ice coastal areas, inland areas, lakes, streams, glaciers, the Greenland Ice Cap, and the Ward-Hunt Ice Shelf. Questions arising from analysis of the imagery led to a winter experiment in which study was concentrated on the temperature differences that develop at shorelines, hut a number of secondary studies were also conducted. Aerial radiometric data and photographs were correlated with ground data which included subsurface temperatures in the soil, ice, and snow on both sides of a shoreline. A classification system for thermal features exhibited by arctic terrain and preliminary criteria for seasonal maps was developed. It was found that: (1) a thermal condition, named the "cold fringe effect," that allows the identification of areas where sea and lake ice is frozen to the bottom develops late in winter, (2) it may he possible to map snow depths from surface temperature on undisturbed ice, and (3) useful infrared data can he obtained under very hazy and moderately windy conditions. Secondary studies included solar heating effects and infrared transmission through haze. Numerous examples of thermal imagery are included, Six appendices present basic principles; thermal and radiation properties of snow, ice and soil; data; and description of equipment.
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