NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Effects of Surface BRDF on the OMI Cloud and NO2 Retrievals: A New Approach Based on Geometry-Dependent Lambertian Equivalent Reflectivity (GLER) Derived from MODISThe Ozone Monitoring Instrument (OMI) cloud and NO2 algorithms use a monthly gridded surface reflectivity climatology that does not depend upon the observation geometry. In reality, reflection of incoming direct and diffuse solar light from land or ocean surfaces is sensitive to the sun sensor geometry. This dependence is described by the bidirectional reflectance distribution function (BRDF). To account for the BRDF, we propose to use a new concept of geometry-dependent Lambertian equivalent reflectivity (GLER). Implementation within the existing OMI cloud and NO2 retrieval infrastructure requires changes only to the input surface reflectivity database. GLER is calculated using a vector radiative transfer model with high spatial resolution BRDF information from MODIS over land and the Cox Munk slope distribution over ocean with a contribution from water-leaving radiance. We compare GLER and climatological LER at 466 nm, which is used in the OMI O2-O2cloud algorithm to derive effective cloud fractions. A detailed comparison of the cloud fractions and pressures derived with climatological and GLERs is carried out. GLER and corresponding retrieved cloud products are then used as input to the OMI NO2 algorithm. We find that replacing the climatological OMI-based LERs with GLERs can increase NO2 vertical columns by up to 50 % in highly polluted areas; the differences include both BRDF effects and biases between the MODIS and OMI-based surface reflectance data sets. Only minor changes to NO2 columns (within 5 %) are found over unpolluted and overcast areas.
Document ID
20180002222
Acquisition Source
Goddard Space Flight Center
Document Type
Presentation
Authors
Vasilkov, Alexander
(Science Systems and Applications, Inc. Lanham, MD, United States)
Qin, Wenhan
(Science Systems and Applications, Inc. Lanham, MD, United States)
Krotkov, Nickolay
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Lamsal, Lok
(Universities Space Research Association Columbia, MD, United States)
Spurr, Robert
(RT Solutions, Inc. Cambridge, MA, United States)
Haffner, David
(Science Systems and Applications, Inc. Lanham, MD, United States)
Joiner, Joanna
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Yang, Eun-Su
(Science Systems and Applications, Inc. Lanham, MD, United States)
Marchenko, Sergey
(Science Systems and Applications, Inc. Lanham, MD, United States)
Date Acquired
April 10, 2018
Publication Date
April 19, 2017
Subject Category
Numerical Analysis
Meteorology And Climatology
Earth Resources And Remote Sensing
Report/Patent Number
GSFC-E-DAA-TN54866
Meeting Information
Meeting: The A-Train Symposium
Location: Pasadena, CA
Country: United States
Start Date: April 19, 2017
End Date: April 21, 2017
Sponsors: NASA Headquarters
Funding Number(s)
CONTRACT_GRANT: NNG11HP16A
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
MODIS BRDF OMI clouds NO2 GLER
No Preview Available