Estimation of incident Photosynthetically Active Radiation from MODIS Data

dc.contributor.authorLiang, Shunlin
dc.contributor.authorZheng, Tao
dc.contributor.authorLiu, Ronggao
dc.contributor.authorFang, Hongliang
dc.contributor.authorTsay, Si-Chee
dc.contributor.authorRunning, Steven
dc.description.abstractIncident 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.en
dc.format.extent3639609 bytes
dc.identifier.citationLiang, S., T. Zheng, R. Liu, H. Fang, S. C. Tsay, S. Running, (2006), Estimation of incident Photosynthetically Active Radiation from MODIS Data, Journal of Geophysical Research - Atmosphere, 111, D15208, doi:10.1029/2005JD006730en
dc.publisherAmerican Geophysical Unionen
dc.relation.isAvailableAtCollege of Behavioral & Social Sciencesen_us
dc.relation.isAvailableAtDigital Repository at the University of Marylanden_us
dc.relation.isAvailableAtUniversity of Maryland (College Park, Md.)en_us
dc.subjectphotosynthetically active radiationen
dc.subjectcarbon cycle modelingen
dc.subjectoderate Resolution Imaging Spectrometeren
dc.subjecttop-of-atmosphere radianceen
dc.subjectsurface reflectanceen
dc.titleEstimation of incident Photosynthetically Active Radiation from MODIS Dataen


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