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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 10 | Copyright
Atmos. Meas. Tech., 11, 5813-5825, 2018
https://doi.org/10.5194/amt-11-5813-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 23 Oct 2018

Research article | 23 Oct 2018

Screening for snow/snowmelt in SNPP VIIRS aerosol optical depth algorithm

Jingfeng Huang1,2,a, Istvan Laszlo2,3, Lorraine A. Remer4, Hongqing Liu2,5, Hai Zhang2,5, Pubu Ciren2,5, and Shobha Kondragunta2 Jingfeng Huang et al.
  • 1Earth Resources Technology Inc., Laurel, MD, USA
  • 2National Oceanic and Atmospheric Administration, National Environmental Satellite, Data, and Information Service, Center for Satellite Applications and Research, College Park, MD, USA
  • 3Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD, USA
  • 4Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Baltimore, MD, USA
  • 5I. M. Systems Group, Inc., College Park, MD, USA
  • aformerly at: Earth System Science Interdisciplinary Center (ESSIC)/Cooperative Institute for Climate and Satellites (CICS)-Maryland, University of Maryland, College Park, MD, USA

Abstract. The Visible Infrared Imaging Radiometer Suite (VIIRS) on board the Suomi National Polar-orbiting Partnership (S-NPP) spacecraft provides validated daily global aerosol optical depth (AOD) retrievals; however, a close examination of the VIIRS aerosol product identified residual snow and snowmelt contamination, resulting generally in an overestimation of AOD. The contamination was particularly evident over Northern Hemisphere high-latitude regions during the spring thaw. To improve the product performance, we introduced a new empirical snow and snowmelt screening scheme that combines a normalized difference snow index (NDSI)- and brightness temperature (BT)-based snow test, a snow adjacency test and a spatial homogeneity test (a.k.a. spatial filter). Testing of retrievals for 18 May 2014 indicated that, compared to the previous, visible reflectance anomaly (VRA)-based snow test, the new NDSI- and BT-based snow test screened out an additional 3.44% of VIIRS AOD retrievals, most of which were over high latitudes experiencing snowmelt. The new snow adjacency test and the homogeneity test degraded another 5.57% and 0.26%, respectively, otherwise good-quality AOD retrievals. For the VIIRS–AERONET (Aerosol Robotic Network) matchups over Northern Hemisphere high-latitude regions during 3 years of spring (2013–2015), the new scheme also effectively screened out a significant number of the matchups that had anomalously high positive biases attributable to snow and snowmelt contamination. The new snow and snowmelt screening scheme was transferred to the Interface Data Processing Segment (IDPS) VIIRS aerosol algorithm on 22 June 2015. Subsequently no significant snow and snowmelt contamination was found during spring 2016. The scheme is also implemented in the new Enterprise VIIRS aerosol algorithm in the National Oceanic and Atmospheric Administration (NOAA) Enterprise Processing System (EPS) that became operational in 2017.

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A new snow/snowmelt screening approach – combining a normalized difference snow index (NDSI)- and brightness temperature (BT)-based snow test, snow adjacency test and spatial filter – is proposed to significantly reduce the snow/snowmelt contamination in the NOAA’s operational Visible Infrared Imaging Radiometer Suite (VIIRS) aerosol optical depth (AOD) product, particularly over Northern Hemisphere high-latitude regions during spring thaw.
A new snow/snowmelt screening approach – combining a normalized difference snow index (NDSI)-...
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