Exploring systematic offsets between aerosol products from the two MODIS sensors
MetadataShow full item record
Type of Work20 pages
Citation of Original PublicationRobert C. Levy, Shana Mattoo, Virginia Sawyer, Yingxi Shi, Peter R. Colarco, Alexei I. Lyapustin, Yujie Wang, Lorraine A. Remer: Exploring systematic offsets between aerosol products from the two MODIS sensors, Atmospheric Measurement Techniques, Volume 11 issue 7, 4073-4092, https://doi.org/10.5194/amt-11-4073-2018, 2018.
RightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
Attribution 4.0 International (CC BY 4.0)
Subjectsoverlapping time series
Goddard Earth Observing System
measurement of global aerosol loading and optical properties
observations of spectral reflectance and radiance
dark-target (DT) aerosol retrieval algorithm
Moderate Resolution Imaging Spectroradiometer sensors
global aerosol optical depth
analysis of overlapping time series
variability of measurements
global differences between Terra and Aqua aerosol products
Long-term measurements of global aerosol loading and optical properties are essential for assessing climate-related questions. Using observations of spectral reflectance and radiance, the dark-target (DT) aerosol retrieval algorithm is applied to Moderate Resolution Imaging Spectroradiometer sensors on both Terra (MODIS-T) and Aqua (MODIS-A) satellites, deriving products (known as MOD04 and MYD04, respectively) of global aerosol optical depth (AOD at 0.55µm) over both land and ocean, and an Ångström exponent (AE derived from 0.55 and 0.86µm) over ocean. Here, we analyze the overlapping time series (since mid-2002) of the Collection 6 (C6) aerosol products. Global monthly mean AOD from MOD04 (Terra with morning overpass) is consistently higher than MYD04 (Aqua with afternoon overpass) by ∼13% (∼0.02 over land and ∼0.015 over ocean), and this offset (MOD04 – MYD04) has seasonal as well as long-term variability. Focusing on 2008 and deriving yearly gridded mean AOD and AE, we find that, over ocean, the MOD04 (morning) AOD is higher and the AE is lower. Over land, there is more variability, but only biomass-burning regions tend to have AOD lower for MOD04. Using simulated aerosol fields from the Goddard Earth Observing System (GEOS-5) Earth system model and sampling separately (in time and space) along each MODIS-observed swath during 2008, the magnitudes of morning versus afternoon offsets of AOD and AE are smaller than those in the C6 products. Since the differences are not easily attributed to either aerosol diurnal cycles or sampling issues, we test additional corrections to the input reflectance data. The first, known as C6+, corrects for long-term changes to each sensor's polarization sensitivity and the response versus the scan angle and to cross-calibration from MODIS-T to MODIS-A. A second convolves the detrending and cross-calibration into scaling factors. Each method was applied upstream of the aerosol retrieval using 2008 data. While both methods reduced the overall AOD offset over land from 0.02 to 0.01, neither significantly reduced the AOD offset over ocean. The overall negative AE offset was reduced. A collection (C6.1) of all MODIS Atmosphere products was released, but we expect that the C6.1 aerosol products will maintain similar overall AOD and AE offsets. We conclude that (a) users should not interpret global differences between Terra and Aqua aerosol products as representing a true diurnal signal in the aerosol. (b) Because the MODIS-A product appears to have an overall smaller bias compared to ground-truth data, it may be more suitable for some applications. However (c), since the AOD offset is only ∼0.02 and within the noise level for single retrievals, both MODIS products may be adequate for most applications.
The following license files are associated with this item:
- Creative Commons
Except where otherwise noted, this item's license is described as This item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
Showing items related by title, author, creator and subject.
An Investigation of Raman Lidar Aerosol Measurements and their Application to the study of the Aerosol Indirect Effect Russo, Felicita (2007-11-26)The problem of the increasing global atmospheric temperature has motivated a large interest in studying the mechanisms that can influence the radiative balance of the planet. Aerosols are responsible for several radiative ...
Advancements in the Aerosol Robotic Network (AERONET) Version 3 database – automated near-real-time quality control algorithm with improved cloud screening for Sun photometer aerosol optical depth (AOD) measurements Giles, David M.; Sinyuk, Alexander; Sorokin, Mikhail G.; Schafer, Joel S.; Smirnov, Alexander; Slutsker, Ilya; Eck, Thomas F.; Holben, Brent N.; Lewis, Jasper R.; Campbell, James R.; Welton, Ellsworth J.; Korkin, Sergey V.; Lyapustin, Alexei I. (Copernicus Publications on behalf of the European Geosciences Union, 2019-01-11)The Aerosol Robotic Network (AERONET) has provided highly accurate, ground-truth measurements of the aerosol optical depth (AOD) using Cimel Electronique Sun–sky radiometers for more than 25 years. In Version 2 (V2) of the ...
Sawamura, Patricia (2013-01-01)Over the past decade the development of inversion techniques for the retrievals of aerosol microphysical properties (e.g. effective radius, volume and surface-area concentrations) and aerosol optical properties (e.g. complex ...