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

2

20130909

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

3

20130909

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)

4

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

5

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

6

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

8

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