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1 Aug 11, 2017
ENHANCEMENT OF THE AVHRR–BASED BRIGHTNESS TEMPERATURE DATA

The major goal of the present article is to investigate the Brightness Temperature (BT) stability in the NOAA/NESDIS Global Vegetation Index (GVI) using over 20 years of data, which was collected from five NOAA series satellites. An empirical distribution function (EDF) was developed to reduce the long-term inaccuracy of the BT data derived from the AVHRR sensor on NOAA polar orbiting satellite. The instability of data results from orbit degradation as well as from the circuit drifts over the life of a satellite. Degradation of BT over time and shifts of BT between the satellites were estimated using the China data set, because it includes a wide variety of different ecosystems represented globally. It was found that the data for six particular years, four of which were consecutive, are not stable compared to other years because of satellite orbit drift, AVHRR sensor degradation, and satellite technical problems, including satellite electronic and mechanical satellite systems deterioration. The data for paired years for the NOAA-7, NOAA-9, NOAA-11, NOAA-14, and NOAA-16 were assumed to be standard because the crossing time of satellite over the equator (between 13:30 and 15:00 hours) maximized the value of the coefficients. These years were considered the standard years, while in other years the quality of satellite observations significantly deviated from the standard. The deficiency of data for the affected years were normalized or corrected by using the EDF method and compared with the standard years. These normalized values were then utilized to estimate new BT time series that show significant improvement of BT data for the affected years....

Authors: Md. Z. Rahman, Leonid Roytman , Abdelhamid Kadik, Dilara A. Rosy.

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