overview of case studies of viirs aerosol products for operational applications amy huff...

Overview of Case Studies of VIIRS Aerosol Products for Operational Applications

Amy HuffPennsylvania State University

VIIRS Aerosol Science and Operational Users WorkshopNovember 22, 2013

S-NPP VIIRS Products on IDEA• True color imagery (RGB): – Combination of red, green, and blue bands of VIIRS– 750 m resolution– Looks like a

photograph– Useful for

identifying areas of smoke, haze, and dust

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S-NPP VIIRS Products on IDEA• Aerosol Optical Thickness (AOT): – Analogous to AOD from MODIS– Unitless measurement; represented on a color-coded scale

ranging from 0 to 1– Related to PM2.5 in

atmosphere – Complements RGB

imagery– Clouds block

measurement of AOT

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VIIRS Intermediate Product (IP) AOT

• 750 m resolution• 4 quality flags (see Product Description): High,

Degraded, Excluded, Not Produced• IP AOT on IDEA Case Study Site:– IP High: cloud-free IP AOT of the highest quality (use for

quantitative applications)– IP High*: IP High AOT plus degraded AOT due to cirrus clouds

or soil-dominated surfaces (use for qualitative applications – comparable to MODIS Aqua AOD)

– IP High & Degraded: IP High AOT plus all degraded AOT (see Table 2 in the Product Description for a list of degraded conditions)

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VIIRS Environmental Data Record (EDR) AOT

• Aggregated from IP AOT retrievals in a 8 × 8 pixel box• 6 km resolution• 3 quality flags (see Product Description): High, Medium,

Low• EDR quality flag based on number of IP AOT pixels with

a particular quality flag falling inside or outside a threshold number – e.g., EDR High AOT are comprised of >16 IP pixels (out of a

possible 64) and all of the IP pixels are IP High quality

• EDR AOT on IDEA Case Study Site:– EDR High– EDR High & Medium

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IP/EDR AOT Coverage Comparison• Spatial resolution of IP (750 m) vs. EDR (6 km) pixels• < 16 IP High AOD pixels available (requirement for EDR High AOT)• Lat/Lon used for center of IP AOT pixels and EDR AOT pixels is

different

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IP High (750m) EDR High (6 km)

Validation Status of VIIRS AOT Products

• VIIRS AOT products are provisional:– Product quality may not be optimal

• Product accuracy is determined for a broader (but still limited) set of conditions

• No requirement to demonstrate compliance with specifications

– Incremental product improvements are still occurring – The general research community is encouraged to

participate in the QA and validation of the product, but users need to be aware that product validation and QA are ongoing

– Users are urged to consult the EDR product status document prior to use of the data in publications

– The data are ready for operational evaluation7

IDEA Case Study Website

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select date

select version of AOT and quality flags

change RGB/AOT opacity

visualization options

download imagery

select CONUS or global imagery

zoom in/out

Case Study Breakout Sessionhttp://www.star.nesdis.noaa.gov/smcd/spb/aq/viirs_workshop_2013/

• 2 case studies: July 2 (fires in southeastern Canada) and Sept 9 (Rim fire in California)

• Step 1: break into groups of 2-3 (need at least 1 laptop)• Step 2: review Power Point files of air quality and

meteorological conditions for each day• Step 3: review operational S-NPP VIIRS AOT and RGB

imagery (use Case Study Worksheet)• Step 4: answer questions on Case Study Questionnaire

about the AOT and RGB products – feedback for NOAA• Step 5: group discussion on VIIRS products (after the

break)9