A path reflectance correction for improved cloud detection using the VIIRS 412 nm band

ABSTRACT

Satellite data collected in the ultraviolet region of the electromagnetic spectrum have proven useful in the detection of clouds over desert backgrounds and in the discrimination between clouds and heavy aerosols over ocean surfaces. However, both of these applications within the Visible Infrared Imager Radiometer Suite (VIIRS) cloud mask (VCM) algorithm exploiting data collected in the 412 nm band were found to demonstrate a scan angle dependence that corresponds to variations in path reflectance caused by Rayleigh (i.e. molecular) scattering in this bandpass. As a consequence, it became necessary to correct the calibrated VIIRS 412 nm reflectances for molecular path reflectance prior to applying the logic previously described in earlier publications. The new procedures developed to make this path reflectance correction are presented in this article, along with results created using the VCM algorithm with and without those corrections being applied to the VIIRS observations. VCM performance is based upon comparisons to manually generated cloud masks created from VIIRS imagery. It is concluded that a correction for path reflectance variations is needed to fully exploit the cloud detection and typing algorithms within the VCM algorithm that exploit data collected in this 412 nm VIIRS band.

Acknowledgments

VIIRS scene data referenced in this publication were acquired by DKK under ASRC Mets II sub-contract #2855055 in support of Northrop Grumman as part of the work performed under their NPOESS contract # F04701-02-C-0502. The views, opinions, and findings contained in this report are those of the authors and should not be construed as an official position of Northrop Grumman, ASRC, or NOAA.

Disclosure statement

No potential conflict of interest was reported by the authors.