Transcript Slide 1
A33C-0161 On the New Satellite Aerosol Measurements for Atmospheric Applications: VIIRS Aerosol Products JPSS/NPP/VIIRS
The Joint Polar Satellite System (JPSS) is the USA's next generation polar-orbiting operational environmental satellite system. JPSS will provide operational continuity of satellite-based observations and products currently obtained from the Suomi National Polar-orbiting Partnership (NPP) mission.
NPP and JPSS are expected to provide a continuation of major long-term observations by the Earth Observing System such as Terra, Aqua, and Aura to enhance our understanding of climate change processes.
Ho-Chun Huang
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* , Jingfeng Huang
1
, Istvan Laszlo
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, Shobha Kondragunta
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, Hongqing Liu
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, Lorraine Remer
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, and Andrew Sayer
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* [email protected]
1
UMD/ESSIC at NOAA/NESDIS/STAR
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NOAA/NESDIS/STAR
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IMSG at NOAA/NESDIS/STAR
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UMBC
5
GESTAR/USRA at NASA GSFC
Visible Infrared Imaging Radiometer Suite (VIIRS) is a multi-spectral scanning radiometer (22 bands between 0.4μm and 12μm) on-board JPSS/NPP with spatial resolution for 16 bands at 750m and 5 bands at 325m. The spatial resolution of Aerosol Optical Thickness (AOT) Environment Data Record (EDR/ Level 2) is 6 km at nadir compared to 10km at nadir for Moderate-Resolution Imaging Spectroradiometer (MODIS).
Separate algorithms are used for aerosol retrieval over land and ocean. The over-land aerosol algorithm is based on MODIS surface Reflectance (MOD09 Collection 5) algorithm and the over-ocean algorithm is derived from the MODIS Aerosol (MOD04 Collection 5) algorithm.
AOT and aerosol type are retrieved simultaneously by minimizing the difference between observed and calculated reflectance in multiple channels.
Beta-release of VIIRS aerosol products
VIIRS aerosol products include AOT, Aerosol Particle Size Parameter (APSP), and Suspended Matter (SM).
The beta release of VIIRS aerosol data is available to the community to allow users to gain familiarity with data formats and parameters. They include AOT EDR of both over land and ocean. APSP (Angstrom Exponent) is beta both over land and ocean, except that we do not recommend using it over land.
Comparisons with
M
aritime
A
erosol
N
etwork AOT
MAN AOT is a ship-based aerosol optical thickness measurement that uses the Microtops II sun photometers. MAN data were collected follow AERONET protocol for observations and data processing,
http://aeronet.gsfc.nasa.gov/new_web/maritime_aerosol_network.html
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Period from May 2, 2012 to October 14, 2012.
MAN Level 1.5 series average AOT.
VIIRS AOT EDRs with best quality (QF=3) retrievals and oceanic EDR .
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Match-up criteria for VIIRS AOT EDR and MAN AOT VIIRS granule scanned times of selected AOT EDRs are within ± 30 minutes of MAN observation.
The VIIRS AOT EDR that has the shortest distance from MAN observation and within 2km radius from MAN observation is match-up with MAN AOT for comparison.
Figure 2 Scatter plot for AOT match-up between VIIRS EDR and MAN.
The dash line is 1:1 and the dotted line is the expected
±
5% accuracy range.
Figure 3 The VIIRS AOT EDR (3a) and the quality flag of AOT retrievals (QF, 3b) in a match-up area (red box, centered at MAN observation). Color coded circles are VIIRS AOT EDR in (3a) and EDR QF from high (=3) to lowest (=0) in (3b). MAN AOT is marked with a red circle and colored coded square in (3a) and a red circle with a cross in (3b). Over ocean, the closest VIIRS AOT EDR with lower AOD quality may also be a good retrieval.
(a) (b) To understand the present performance of VIIRS aerosol products at beta level and the difference of AOT retrievals between VIIRS and MODIS for long-term climatic applications, this study will focus on AOT comparisons between VIIRS EDR and AErosol RObotic NETwork (AERONET), Maritime Aerosol Network (MAN), and MODIS.
Comparisons with
AE
rosol
RO
botic
NET
work AOT
Period from May 2, 2012 to October 14, 2012.
(Contact: Dr. Jingfeng Huang, [email protected])
Level 1.5 AERONET Direct Sun Algorithm,
http://aeronet.gsfc.nasa.gov
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VIIRS/MODIS AOT EDR with best quality (QF=3) retrievals.
Match-up criteria
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AERONET observation is within ± 30 minutes of VIIRS/MODIS granule scanned time Collocated VIIRS/MODIS AOT EDR and AERONET site is used.
Figures 1a and 1d show AOT comparisons between VIIRS EDR and AERONET for the present performance of VIIRS AOT EDR retrievals. The performance can be used to compare to that of MODIS (figs 1b-c, 1e-f) to show the relative changes of retrieved AOT when transition from MODIS AOT to VIIRS AOT.
Figure 1 Scatter plots for AOT match-up between AERONET and VIIRS and MODIS (on-board Aqua & Terra). Figs. 1a 1c show comparisons in coastal area with different satellite sensors, while figs. 1d-1f show results over land.
Table 1 The statistics of AOT comparisons between VIIRS EDR, MODIS, AERONET, and MAN.
OCEAN VIIRS COASTAL VIIRS Aqua MODIS Terra MODIS LAND VIIRS Aqua MODIS Terra MODIS Mean Bias 0.007
Mean Bias 0.013
0.007
0.022
Mean Bias 0.114
0.005
-0.019
RMSE 0.070
RMSE 0.066
0.057
0.056
RMSE 0.235
0.142
0.136
R 0.920
R 0.880
0.917
0.910
R 0.606
0.842
0.844
(a) (d) (b) (e) (c) (f)
Summary
Different match-up criteria also were used (not shown) in this study and results are the same or marginally different. The conclusions stated won't change among criteria. This study shows that the performance of VIIRS AOT EDR retrievals is very good over ocean. In coastal areas, VIIRS AOT EDR overestimates AOT but it is comparable to that of MODIS AOT.
However, over land, the overestimates of VIIRS AOT EDR retrieval is much higher than that of MODIS AOT.
VIIRS aerosol retrieval algorithms will continue to improve toward the Provisional status. During the beta-release of VIIRS aerosol products, users are encouraged to download VIIRS aerosol products and familiarized with the procedure.
VIIRS aerosol CAL/VAL team appreciates users’ feedback on the data flow and data quality. Users’ opinion are valuable toward a better performance of VIIRS aerosol retrievals.
The primary data source for NPP products is through NOAA’s Comprehensive Large Array-Data Stewardship System (CLASS) web interface,
http://www.class.noaa.gov
. Subscriptions to CLASS are needed to allow users to set up a routine data ordering and transfer. More information of NPP data access and order procedure can be found in “User Guides”,
http://www.star.nesdis.noaa.gov/jpss/ATBD.php#S397092
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Acknowledgement: Authors thank PIs and their staff for establishing and maintaining MAN sites used in this study
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