Document Type
Article
Publication Title
Journal of Geophysical Research
Publisher
American Geophysical Union
Publication Date
2006
Volume
111
Disciplines
Ecology and Evolutionary Biology
Abstract
Incident photosynthetically active radiation (PAR) is a key variable needed by almost all terrestrial ecosystem models. Unfortunately, the current incident PAR products estimated from remotely sensed data at spatial and temporal resolutions are not sufficient for carbon cycle modeling and various applications. In this study, the authors develop a new method based on the look-up table approach for estimating instantaneous incident PAR from the polar-orbiting Moderate Resolution Imaging Spectrometer (MODIS) data. Since the top-of-atmosphere (TOA) radiance depends on both surface reflectance and atmospheric properties that largely determine the incident PAR, our first step is to estimate surface reflectance. The approach assumes known aerosol properties for the observations with minimum blue reflectance from a temporal window of each pixel. Their inverted surface reflectance is then interpolated to determine the surface reflectance of other observations. The second step is to calculate PAR by matching the computed TOA reflectance from the look-up table with the TOA values of the satellite observations. Both the direct and diffuse PAR components, as well as the total shortwave radiation, are determined in exactly the same fashion. The calculation of a daily average PAR value from one or two instantaneous PAR values is also explored. Ground measurements from seven FLUXNET sites are used for validating the algorithm. The results indicate that this approach can produce reasonable PAR product at 1 km resolution and is suitable for global applications, although more quantitative validation activities are still needed.
Keywords
PAR; MODIS; carbon cycle
DOI
10.1029/2005JD006730
Recommended Citation
Liang, Shunlin; Zheng, Tao; Liu, Ronggao; Fang, Hongliang; Tsay, Si-Chee; and Running, Steven W., "Estimation of Incident Photosynthetically Active Radiation From Moderate Resolution Imaging Spectrometer Data" (2006). Ecosystem and Conservation Sciences Faculty Publications. 21.
https://scholarworks.umt.edu/decs_pubs/21
Comments
Accepted for publication in Journal of Geophysical Research. Copyright 2006 American Geophysical Union. Further reproduction or electronic distribution is not permitted.