Wednesday, 17 January 2007
Differentiating between clouds and aerosol during the NPOESS era
217D (Henry B. Gonzalez Convention Center)
The VIIRS Cloud Mask (VCM) algorithm identifies cloud-contaminated pixels that are essential to produce a number of NPOESS cloud products in addition to other products that are created under cloud-free conditions. The performance of algorithms that expect cloud-free conditions, e.g. sea surface temperature, can be severely degraded when undetected clouds “leak” into the analysis. Therefore, the VCM has been designed to detect all cloudy pixels, including edge effects, while simultaneously ensuring cloud-free pixels are not “falsely” flagged as cloud-contaminated, which would impact the performance of other VIIRS cloud algorithms, e.g. used to retrieve the cloud optical property products. In addition, the VCM algorithm must also differentiate between clouds and atmospheric aerosols, which may have similar spectral characteristics in most VIIRS bands. This poster highlights the NPOESS requirements for automated cloud detection and the approaches used in the VCM algorithm to minimize both leakage and false alarm rates while differentiating between clouds and a variety of atmospheric aerosols, e.g. smoke, volcanic ash, and blowing sand. The presentation shows that the goal of creating a single cloud mask for use in products needed by the entire NPOESS user community can be satisfied by the VCM algorithm.