Impact of long-range transport over the Atlantic Ocean on Saharan dust optical and microphysical properties

Abstract

Abstract. Mineral dust aerosol can be a major driver of aerosol climatology in regions distant from the sources. This study addresses the change of columnar aerosol properties when mineral dust arrives to the Caribbean Basin after transport from Africa over the Atlantic Ocean. We use data from NASA Aerosol Robotic Network (AERONET) sites in five Caribbean and two West African sites to characterize changes in aerosol properties: aerosol optical depth, size distribution, single scattering 15 albedo, and refractive indexes. After obtaining local aerosol climatology in each area, the air mass connections between West Africa and Caribbean Basin have been investigated by means of air mass back trajectories. Over the period 1996-2014 we identify 3174 connection days, on average, 167 connection days per year. Among these, 1162 pairs of data present aerosol data in Caribbean sites with corresponding aerosol observations in Western Africa sites ~5-7 days before. Of these 1162 days, 484 meet the criteria to be characterized as mineral dust outbreaks. Based on these days we observe the following 20 changes in aerosol-related properties in transiting the Atlantic: AOD decreases about 0.16 or -30%; the volume particle size distribution shape shows no changes; single scattering albedo, refractive indexes, and asymmetry factor remain unchanged; the difference in the effective radius in West African area with respect to Caribbean Basin is between 0 and +0.3 µm; and half of the analyzed cases present predominance of non-spherical particles in both areas.

Determining the desert dust aerosol presence in the Mantaro Valley, Peru

“…Los aerosoles de origen desértico y el polvo mineral, constituyen un tipo común de material particulado en suspensión, que caracteriza las regiones áridas del planeta y cuyo principal mecanismo de generación es la erosión debido al viento [2]. Estos aerosoles pueden ser transportados a enormes distancias desde su región de origen, como es el caso de los aerosoles desérticos que se originan en el Sahara y alcanzan el Caribe [3] y afectar las condiciones del tiempo y el clima en zonas ubicadas a grandes distancias de la fuente donde se han generado [4]. El polvo mineral en suspensión es una de las fuentes de especies alérgicas potenciales, constituyendo uno de los problemas que agrava la salud humana [5], como la alergia de tipo estacional y enfermedades respiratorias, las cuales pueden coincidir con elevadas concentraciones de polvo incluyendo el desértico [6,7].…”

Comparison of aerosol optical depth from satellite (MODIS), sun photometer and broadband pyrheliometer ground-based observations in Cuba

“…Based on the assumptions about the properties of the Earth's surface and the aerosol type expected over these surfaces, the MODIS Atmosphere team developed three algorithms for processing MODIS observations (Levy et al, 2013). Regions which appear visually dark from space, referred to as dark target (DT), include the algorithm assumptions for vegetated land surfaces (Kaufman et al, 1997a, b) and for remote ocean regions (Tanré et al, 1997). The third algorithm, called the deep blue (DB) algorithm, includes assumptions for surfaces which are visually bright from space and uses near-UV wavelengths (DB band near 410 nm).…”

“…All of these processes play a key role at a global and regional scales due to the high spatio-temporal variability of aerosol properties. Aerosols can also affect the biosphere and, in particular, humans in several ways: for example, the Saharan dust transported to America across the Atlantic supplies nutrients to the Amazon forest (Swap et al, 1992;Yu et al, 2015). Moreover, in the Caribbean, in addition to aerosols of local origin, dust makes the amount of aerosol exceed air quality standards associated with human health (Prospero and Lamb, 2003;Prospero et al, 2014).…”

“…This comparative analysis does not aim to be a validation study of the MODIS sensor since many works during the long history of the MODIS sensor on the Terra and Aqua platforms have sought to improve its features (these include Kaufman et al, 1997a, b;Tanré et al, 1997;Remer et al, 2002Remer et al, , 2005Remer et al, , 2006Hsu, et al, 2004Hsu, et al, , 2006Hsu, et al, , 2013Levy et al, 2007Levy et al, , 2009Levy et al, , 2010Levy et al, , 2013Levy et al, , 2015Sayer et al, 2013Sayer et al, , 2014 https://darktarget.gsfc.nasa.gov/atbd/overview, last access: 9 April 2018). However, compared to other areas of the world, no studies have been reported in the Caribbean region and in Cuba in particular (Papadimas et al, 2009;Mishchenko et al, 2010;Kahn et al, 2011;Bennouna et al, 2011Bennouna et al, , 2013Witte et al, 2011;Gkikas et al, 2013Gkikas et al, , 2016Levy et al, 2015).…”