Variation in Visual and Near-Infrared Contrast with a Snow Background.

• Main Author: Peck, Lindamae
• Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
• Format: Text
• Language: English
• Published: 1994
• Subjects: Optics; Snow; Ice and Permafrost; *SNOW COVER; *NEAR INFRARED RADIATION; *ALBEDO; INFRARED DETECTION; CONTRAST; ILLUMINATION; REFLECTION; CONSISTENCY; SOILS; SEASONAL VARIATIONS; INFRARED IMAGES; BACKGROUND; VISUAL PERCEPTION; SOLAR RADIATION; MOISTURE; SURFACE TEMPERATURE; DAILY OCCURRENCE; DIURNAL VARIATIONS; VISUAL TARGETS; CONCEALMENT; SUN; WHITE(COLOR); SPN-19950112044; Ice; permafrost
• Online Access: http://www.dtic.mil/docs/citations/ADA289710; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA289710

Visual and near-infrared concealment against a snow cover are considered in terms of the daily and longer-term variation in albedo of a shallow (< or = 26 cm) snow cover. Examples of albedo of a Vermont snow cover demonstrate the influence of time of day (solar angle), incident solar radiation, snow depth, and snow wetness. Most albedos felt within the range 0.75-0.98. The most consistent variation was a decrease in albedo during the morning as the sun angle increased and a corresponding increase with decreasing sun angle in the afternoon. Albedo was low when the snow surface temperature indicated melting was occurring or when an increase in temperature of the soil beneath the snow cover indicated solar radiation was being absorbed by the soil. Examples of the diurnal variation in sun angle and the seasonal variation in maximum potential solar radiation, as calculated from site latitude and longitude and calendar date, are presented. (AN)