Night time detection of Saharan dust using infrared window channels: Application to NPP/VIIRS

Abstract

A Saharan Dust Index (SDI) has been produced operationally since 2006 from Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI) data. This SDI, based on brightness temperatures (BTs) at 3.9, 8.7, 10.8 and 12.0μm, has been used in the Ocean and Sea Ice Satellite Application Facility (OSI-SAF) Sea Surface Temperature (SST) chain to detect Saharan dust and correct for its effect on SST calculations. OSI-SAF has developed a processing chain to derive Sea Surface Temperature (SST) from the Suomi National Polar-orbiting partnership (NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) data. In this framework, an SDI algorithm adapted to VIIRS data has been developed. Consistency between various SDI derived from various sensors is essential in the OSI-SAF context. Without absolute definition of this parameter, we have adopted the Meteosat-9 nominal SDI values as reference. In this paper we present a new method to define SDI algorithms, based on the use of simulated BTs contaminated by aerosols at various concentrations and altitudes. This method has been applied to VIIRS data. It shows consistent results with the original 2006 method and a simple regression against Meteosat-9 SDI values when compared to the operational Meteosat-9 SDI. This new method can be used to prepare SDI equations for any sensor with adequate channels once their radiometric characteristics are known. In addition, it ensures consistency with our reference SDI.