Abstract
Abstract. On 16–17 February 2020, dust within the Saharan Air Layer (SAL) from western Africa moved over the eastern Atlantic Ocean. Satellite imagery and products from the ABI on GOES-16, VIIRS on NOAA-20, and CALIOP on CALIPSO, along with retrieved values of layer and total precipitable water (TPW) from MIRS and NUCAPS, respectively, were used to identify dust within the SAL over the eastern Atlantic Ocean. Various satellite imagery and products were also used to characterize the distribution of water vapor within the SAL. There was a distinct pattern between dust detection and dust masking and values of precipitable water. Specifically, dust was detected when values of layer TPW were approximately 14 mm; in addition, dust was masked when values of layer TPW were approximately 28 mm. In other words, water vapor masked infrared dust detection if sufficient amounts of water vapor existed in a column. Results herein provide observational support to two recent numerical studies that concluded water vapor can mask infrared detection of airborne dust.
Highlights
For over 45 years, satellite data have been used to detect airborne dust
This paper focuses on a dust plume associated with the Saharan Air Layer (SAL) that moved from western Africa to the eastern Atlantic Ocean, the lack of a blue band (∼ 0.47 μm) on Spinning Enhanced Visible and InfraRed Imager (SEVIRI), which is onboard METEOSAT Second Generation (MSG)-11, whose sub-point is the intersection of the prime meridian and the Equator, prevents the generation of Geo/True-Color imagery
This paper examined satellite observations of a dust plume associated with the SAL that moved from western Africa westward over the eastern Atlantic Ocean
Summary
For over 45 years, satellite data have been used to detect airborne dust. Detection of dust has been explored with the use of low earth orbiting (LEO) sensors such as the (i) Moderate Resolution Imaging Spectroradiometer (King et al, 1992), (ii) Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP; Winker et al, 2009), and (iii) Temperature Humidity Infrared Radiometer and Image Dissector Camera System (both onboard Nimbus-4; Shenk and Curran, 1974). Each of the above studies focused on examining which spectral bands may be used for dust detection, a few did raise the question of possible effects, either advantageously or adversely, of water vapor on dust detection (Ashpole and Washington, 2012; Knippertz and Todd, 2010; Chaboureau et al, 2007; Legrand et al, 2001; Tanre and Legrand, 1991). Results of the 16–17 February 2020 observational study serve to support Banks et al (2019) and Miller et al (2019) by showing that reduced values of water vapor allowed dust associated with the SAL to be both detected and tracked over the eastern Atlantic Ocean.
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