Correction of solar Zenith Angle effect of NOAA AVHRR data for Global Monitoring
Koji Kajiwara, Ryutaro Tateishi
Remote Sensing and Image Research Center, Chiba University
1-33 Yayoi-cho, Chiba 260, Japan
Masao Mastumoto
Faculty Information Science and System Engineering
Kyushu Institute of Technology
680-4 Kawazu Iizuku, Fukuoka 820, Japan
Abstract
Normalized Different Vegetation Index (NDVI) in Global Vegetation Index (GVI) products of AVHRR which provided by NOAA has been widely used for the research of global or continental scale land cover monitoring. Through NDVI was designed to eliminate the change of solar illumination, it is still not completely free from radiometric effects. In this paper, results of the simulation done by using radiative transfer calculation software package LOWTRAN-7 to evaluate the effects of solar zenith angle of the AVHRR Ch. 1 and Ch 2 data, and the factor of temporal variation of solar zenith angle are described. A correction method to remove the effect of low frequency temporal variation of solar zenith angle is also proposed.
Introduction
As some researchers has been pointed out, NDVI values derived from AVHRR data in GVI Product provided by National Oceanic and Atmospheric Administration (NOAA) are affected by solar zenith angle (Singh 1988, Matsumoto et al 1991). The long term global and cover monitoring which uses NDVI should be considered the effect of solar zenith angle especially effect of low frequency variation of solar zenith angle (describe in section 3). This paper aims to clarify the characteristics of the effect of solar zenith angle and to propose a correction method for AVHRR Ch. 1 and Ch. 1 data. In section 3, the characteristics of the radiometric effect by solar zenith angle is clarified by simulation. And the factor which cause the variation of solar zenith angle discussed in section 4. Finally, by the section 5, AVHRR channel data correction method for long-term global monitoring is proposed.
