VIIRS True Color Atmospheric Correction Updates Steve Miller

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VIIRS True Color Atmospheric Correction Updates Steve Miller 14 June 2012

VIIRS True Color Atmospheric Correction Updates Steve Miller 14 June 2012

Overview • VIIRS natural color processing commenced shortly after receipt of first-light data. •

Overview • VIIRS natural color processing commenced shortly after receipt of first-light data. • To expedite initial product suite, the atmospheric corrections necessary for high-quality true color imagery were adopted from the legacy MODIS processing. • The MODIS Blue/Green/Red bands (466, 554, 646 nm) are slightly different than VIIRS (488, 555, 672 nm). • Associated rayleigh optical depths are different, leading to erroneous corrections when applying the MODIS coefficients and tables to VIIRS data. • Correct handling of VIIRS requires a re-calculation of the necessary components, including: Fo, tau_ray, tau_ozone, tau_oxygen, tau_watvap. • Codes adapted from SEADAS software (Eric Vermote and Norman Kuring). • Monochromatic calculation used here (no band weighting), with values for various properties interpolated linearly from the original Sea. Wi. FS band values. Sufficient for qualitative imagery product.

Modifications Coefficient Changes: Bands(MODIS): 3, 4, 1 (466 nm, 554 nm, 646 nm) Bands(VIIRS):

Modifications Coefficient Changes: Bands(MODIS): 3, 4, 1 (466 nm, 554 nm, 646 nm) Bands(VIIRS): 3, 4, 5 (488 nm, 555 nm, 672 nm) F_sun(MODIS): 202. 3, 186. 0, 160. 2 F_sun (VIIRS): 194. 142, 185. 930, 151. 538 ray_taus(MODIS): 0. 189789, 0. 09490, 0. 0492007 ray_taus(VIIRS): 0. 159419, 0. 09420, 0. 04532 raysa(MODIS): 0. 142865, 0. 0801539, 0. 0492007 raysa(VIIRS): 0. 124679, 0. 0797469, 0. 0396954 aoz(MODIS): 0. 015816, 0. 09338, 0. 056965 aoz(VIIRS): 0. 0244511, 0. 09338, 0. 04604 awv(MODIS): 0. 0, 0. 0008, 0. 003539 awv(VIIRS): 0. 0, 0. 0008, 0. 00422421 ao 2(MODIS): 0. 0, 0. 0 ao 2(VIIRS): 0. 0, 0. 0 New Rayleigh Look-Up Tables: ftp: //ftp. cira. colostate. edu/ftp/Miller/NRL/VIIRS_Rayleigh Implementing the simple coefficient and table modifications listed above will result in dramatic improvements to VIIRS true color image quality. The following slides show before/after corrections applied (must run in slide-show mode to toggle imagery).

NEW OLD

NEW OLD

California Coastal Blooms NEW OLD

California Coastal Blooms NEW OLD

NEW OLD

NEW OLD

Next Steps • Evaluate the stability and performance at various sites. • Apply these

Next Steps • Evaluate the stability and performance at various sites. • Apply these new corrections to the VIIRS dust enhancement prototype. • Develop an I-band true color product based on re-bin of M-bands to 375 m resolution using similar techniques as MODIS 250 m.