Estimation of incident photosynthetically active radiation from Moderate Resolution Imaging Spectrometer data

Abstract

[1] 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.

The use of remote sensing in light use efficiency based models of gross primary production: A review of current status and future requirements

“…The MODIS Atmospheric Profile products (MOD04-MOD07) consist of total-ozone burden, atmospheric stability, temperature and moisture profiles, and atmospheric water vapour, measured on a daily basis. Even though the atmospheric interactions of solar irradiance are well understood, a standardized product providing regular observations of global PAR is currently not available (Liang et al, 2006), however, techniques to derive accurate estimates of global PAR using MODIS have been developed (Van Laake and Sanchez-Azofeifa, 2004;Liang et al 2006).…”

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“…A similar approach has been used for Geostationary Operational Environmental Satellites (GOES) (Zheng, Liang, and Wang 2008) and AVHRR (Liang et al 2007b). The basic framework of the algorithms is presented by Liang et al (2006) in the case of estimating incident PAR from MODIS data. The main approach of this algorithm is the use of multitemporal signatures from MODIS data.…”

“…This idea was first applied to analyze the Earth Radiation Budget Experiment (ERBE) data . Liang et al (2006) and Liu et al (2008) generated the PAR and insolation products from MODIS data directly based on the Look-up Table (LUT) method. A similar approach has been used for Geostationary Operational Environmental Satellites (GOES) (Zheng, Liang, and Wang 2008) and AVHRR (Liang et al 2007b).…”

Towards operational remote sensing of forest carbon balance across Northern Europe

“…As an alternative approach, Liang et al (2006) presented a new method for estimating incident PAR using reflectance data from MODIS. Surface and top-of-atmosphere reflectance were used for deriving both diffuse and direct instantaneous PAR.…”