NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Towards a High Temporal Frequency Grass Canopy Thermal IR Model for Background SignaturesIn this paper, we present our first results towards understanding high temporal frequency thermal infrared response from a dense plant canopy and compare the application of our model, driven both by slowly varying, time-averaged meteorological conditions and by high frequency measurements of local and within canopy profiles of relative humidity and wind speed, to high frequency thermal infrared observations. Previously, we have employed three-dimensional ray tracing to compute the intercepted and scattered radiation fluxes and for final scene rendering. For the turbulent fluxes, we employed simple resistance models for latent and sensible heat with one-dimensional profiles of relative humidity and wind speed. Our modeling approach has proven successful in capturing the directional and diurnal variation in background thermal infrared signatures. We hypothesize that at these scales, where the model is typically driven by time-averaged, local meteorological conditions, the primary source of thermal variance arises from the spatial distribution of sunlit and shaded foliage elements within the canopy and the associated radiative interactions. In recent experiments, we have begun to focus on the high temporal frequency response of plant canopies in the thermal infrared at 1 second to 5 minute intervals. At these scales, we hypothesize turbulent mixing plays a more dominant role. Our results indicate that in the high frequency domain, the vertical profile of temperature change is tightly coupled to the within canopy wind speed In the results reported here, the canopy cools from the top down with increased wind velocities and heats from the bottom up at low wind velocities. .
Document ID
20040081284
Document Type
Conference Paper
Authors
Ballard, Jerrell R., Jr. (Army Engineer Research and Development Center Vicksburg, MS, United States)
Smith, James A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Koenig, George G. (Army Cold Regions Research and Engineering Lab. Hanover, NH, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2004
Subject Category
Meteorology and Climatology
Meeting Information
International Society for Optical Engineering Conference(Orlando, FL)
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.