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scientific impact of modis c5 calibration degradation and c6+ improvementsThe Collection 6 (C6) MODIS (Moderate Resolution Imaging Spectroradiometer) land and atmosphere data sets are scheduled for release in 2014. C6 contains significant revisions of the calibration approach to account for sensor aging. This analysis documents the presence of systematic temporal trends in the visible and near-infrared (500 m) bands of the Collection 5 (C5) MODIS Terra and, to lesser extent, in MODIS Aqua geophysical data sets. Sensor degradation is largest in the blue band (B3) of the MODIS sensor on Terra and decreases with wavelength. Calibration degradation causes negative global trends in multiple MODIS C5 products including the dark target algorithm's aerosol optical depth over land and Ångstrom exponent over the ocean, global liquid water and ice cloud optical thickness, as well as surface reflectance and vegetation indices, including the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). As the C5 production will be maintained for another year in parallel with C6, one objective of this paper is to raise awareness of the calibration-related trends for the broad MODIS user community. The new C6 calibration approach removes major calibrations trends in the Level 1B (L1B) data. This paper also introduces an enhanced C6C calibration of the MODIS data set which includes an additional polarization correction (PC) to compensate for the increased polarization sensitivity of MODIS Terra since about 2007, as well as detrending and Terra- Aqua cross-calibration over quasi-stable desert calibration sites. The PC algorithm, developed by the MODIS ocean biology processing group (OBPG), removes residual scan angle, mirror side and seasonal biases from aerosol and surface reflectance (SR) records along with spectral distortions of SR. Using the multiangle implementation of atmospheric correction (MAIAC) algorithm over deserts, we have also developed a detrending and cross-calibration method which removes residual decadal trends on the order of several tenths of 1% of the top-of-atmosphere (TOA) reflectance in the visible and near-infrared MODIS bands B1-B4, and provides a good consistency between the two MODIS sensors. MAIAC analysis over the southern USA shows that the C6C approach removed an additional negative decadal trend of Terra (Delta)NDVI approx.0.01 as compared to Aqua data. This change is particularly important for analysis of vegetation dynamics and trends in the tropics, e.g., Amazon rainforest, where the morning orbit of Terra provides considerably more cloud-free observations compared to the afternoon Aqua measurements.
Document ID
20160005757
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lyapustin, A.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Wang, Y.
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Xiong, X.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Meister, G.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Platnick, S.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Levy, R.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Franz, B.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Korkin, S.
(Universities Space Research Association Columbia, MD, United States)
Hilker, T.
(Oregon State Univ. Corvallis, OR, United States)
Tucker, J.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Hall, F.
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Sellers, P.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Wu, A.
(Sigma Space Corp. Lanham, MD, United States)
Angal, A.
(Science Systems and Applications, Inc. Lanham, MD, United States)
Date Acquired
May 3, 2016
Publication Date
December 10, 2014
Publication Information
Publication: Atmospheric Measurement Techniques
Volume: o 7
Issue: 12
Subject Category
Earth Resources and Remote Sensing
Instrumentation and Photography
Report/Patent Number
GSFC-E-DAA-TN31775
Funding Number(s)
CONTRACT_GRANT: NNG11HP16A
CONTRACT_GRANT: NNX15AT34A
Distribution Limits
Public
Copyright
Other
Keywords
Terra and Aqua
C5 and C6+
MODIS