Introducing VIIRS Aerosol Products

Transcription

1 1 Introducing VIIRS Aerosol Products Shobha Kondragunta NOAA/NESDIS Center for Satellite Applications and Research

2 VIIRS Aerosol Cal/Val Team 2 Name Organization Major Task Kurt F. Brueske IIS/Raytheon Code testing support within IDPS Ashley N. Griffin PRAXIS, INC/NASA JAM Brent Holben NASA/GSFC AERONET observations for validation work Robert Holz UW/CIMSS Product validation and science team support Nai-Yung C. Hsu NASA/GSFC Deep-blue algorithm development Ho-Chun Huang UMD/CICS SM algorithm development and validation Jingfeng Huang UMD/CICS AOT Algorithm development and product validation Edward J. Hyer NRL Product validation, assimilation activities John M. Jackson NGAS VIIRS cal/val activities, liaison to SDR team Shobha Kondragunta NOAA/NESDIS Co-lead Istvan Laszlo NOAA/NESDIS Co-lead Hongqing Liu IMSG/NOAA Visualization, algorithm development, validation Min M. Oo UW/CIMSS Cal/Val with collocated MODIS data Lorraine A. Remer UMBC Algorithm development, ATBD, liason to VCM team Andrew M. Sayer NASA/GESTAR Deep-blue algorithm development Hai Zhang IMSG/NOAA Algorithm coding, validation within IDEA NOAA Team

3 3 Hoff and Christopher, Remote sensing of particulate pollution: have we reached the promised land?, JAWMA, vol. 59, 2009

4 4 Outputs (HDF5): (1) AOT Intermediate Product, IP; (2) AOT Environmental Data Record, EDR; (3) Suspended Matter; (4) Aerosol Model Information; (5) Geolocation file for IP; (6) Geolocation file for EDR. Need to know: IP is a pixel level AOT retrieval; EDR is an aggregate of about 8 X 8 IP pixels; IP product has Navy Aerosol Analysis and Prediction System AOT filled in for pixels with no retrievals but this is not included in EDR; no AOT over inland water bodies; no negative retrievals allowed; no AOTs over 2.0 reported; VIIRS products come with several quality flags that are useful to screen the data. VIIRS Granule: 86 seconds; 48 scan lines; 3040 km swath width; 16 M-bands (412 nm to 12 µm); 768 X 3200 fixed array size per granule.

5 VIIRS vs. MODIS EOS 5 MODIS VIIRS Orbit altitude Equator crossing time Granule size 690 km 824 km 13:30 LT 13:30 LT 5 min 86 sec swath 2330 km 3040 km Pixel nadir 0.5 km 0.75 km Pixel edge 2 km 1.5 km EDR AOT Product nadir EDR AOT Product EOS 10 km 6 km 40 km 12 km

6 IP AOT to EDR AOT 6 IP (750m) EDR (6 km) 8 x 8 750m IP pixels aggregated to 6 km EDRs; For EDR to be of best quality, at least a minimum of 16 out of 64 IP pixels should have best quality AOT; In contrast to VIIRS, MODIS retrieves AOT by averaging 500m reflectances in a 10 km x 10 km grid and discarding the top 50% (25%) and bottom 20% (25%) pixels over land (ocean) During the aggregation process, top 40% and bottom 20% best quality IP pixels are discarded.

7 Daily global mean AOT 7 Production Error Algorithm Upgrade

8 AOT (VIIRS MODIS) 8 Data: February and March 2013 MODIS C5 VIIRS IDPS AOT data mapped to 0.25 o grids AOT data not paired; some sampling differences exist Upgrades to the algorithm to reduce the high bias over land are in the plans. NDVI dependent spectral surface reflectance ratios will be implemented soon.

9 AOT (VIIRS vs. AERONET) 9 Metric VIIRS MODIS Accuracy Precision Uncertainty Metric VIIRS MODIS Accuracy Precision Uncertainty

10 10 Smoke from fires on March 15, 2013 seen in the visible RGB image (left panel) nicely captured in the quantitative retrieval of aerosol optical thickness (right panel). These images are generated at the STAR IDEA (Infusing satellite Data into Environmental Applications) website using direct broadcast SDRs, VCM, and fire hot spot data. Data latency is ~2 hrs. The website ( is routinely accessed by air quality forecasters for satellite aerosol imagery that provides the spatial extent of smoke, dust, and haze.

11 VIIRS true color image of blowing dust from different sources in Alaska on April 28, 2013 VIIRS Pixel Level AOD VIIRS Dust Flag 11

12 Meteorological conditions conducive for an air pollution event (stagnation, limited vertical mixing, high temperatures and warm southerly winds associated with a high pressure) led to a regional haze event resulting in deteriorated air quality on March 22, 2012 over the Great Lakes region ( VIIRS AOT data has gaps due to clouds and nonavailability of retrievals over inland water (lakes). However, haze surrounding the lakes is well captured. VIIRS AOT for this time period not fully characterized and should be used only qualitatively.

13 VIIRS Aerosol Product Applications at EPA 13 -Evidence for EPA s Exceptional Events Rule -Fire Emission Inventory Development -Model Evaluation/Development -AIRNOW Satellite Data Processor

14 Important Dates: Initial instrument check out. Tuning cloud mask parameters Aerosol product at Beta status Software production error Beta status Aerosol product candidate provisional status 28 Oct May Oct 22 Jan Nov 2012 today Red periods: DO NOT USE the product. Beta: Use with caution. Known biases. Provisional: Use data bearing in mind that further validation is ongiong

15 15 All Quality Flags in VIIRS Aerosol IP

16 Data (not SM) are available through CLASS: A back door for data via the IDEA site: Users guide available at: README file under VIIRS aerosol (AOT) at: Other documents are available at: 16

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20 VIIRS Aerosol Algorithm Differences between VIIRS and MODIS Retrieval every pixel (0.75 km resolution) Aggregates AFTER retrieval, discarding outliers in group Robust AOT at standard 6 km resolution at nadir, 12 km at edge LAND: chooses aerosol model LAND: fits to atmospherically corrected surface reflectance ratios LAND Spectral AOT at 11 wavelength with 1 primary wavelength OCEAN: Based on Tanré retrieval OCEAN spectral AOT at 11 wavelength with 1 primary wavelength Heavily dependent on cloud mask from outside MODIS Dark Target Retrieval after grouping pixels (10 km resolution) Aggregates BEFORE retrieval, discarding outliers in group Robust AOT at standard 10 km resolution at nadir, 40 km at edge LAND: mixes fixed fine and coarse models LAND: fits to top of atmosphere reflectances LAND AOT at 3 wavelengths with 1 primary wavelength OCEAN: Based on Tanré retrieval OCEAN spectral AOT at 7 wavelength with 1 primary wavelength Mostly dependent on internal cloud mask. NO negative values. Max AOT = 2.0 YES negative values. Max AOT = Bands used: 0.411, 0.466, (0.550), 0.554, 0.646, 0.856, 1.242, 1.629, µm No level 3 gridded products yet Bands used: 0.412, 0.445, 0.488, (0.550), 0.555, 0.672, 0.746, 0.865, 1.24, 1.61, 2.25 µm Level 3 daily, 8-day, monthly mean