A Global Climatology of Dust Aerosols Based on Satellite Data: Spatial, Seasonal and Inter-Annual Patterns over the Period 2005–2019

Abstract

A satellite-based algorithm is developed and used to determine the presence of dust aerosols on a global scale. The algorithm uses as input aerosol optical properties from the MOderate Resolution Imaging Spectroradiometer (MODIS)-Aqua Collection 6.1 and Ozone Monitoring Instrument (OMI)-Aura version v003 (OMAER-UV) datasets and identifies the existence of dust aerosols in the atmosphere by applying specific thresholds, which ensure the coarse size and the absorptivity of dust aerosols, on the input optical properties. The utilized aerosol optical properties are the multiwavelength aerosol optical depth (AOD), the Aerosol Absorption Index (AI) and the Ångström Exponent (a). The algorithm operates on a daily basis and at 1° × 1° latitude-longitude spatial resolution for the period 2005–2019 and computes the absolute and relative frequency of the occurrence of dust. The monthly and annual mean frequencies are calculated on a pixel level for each year of the study period, enabling the study of the seasonal as well as the inter-annual variation of dust aerosols’ occurrence all over the globe. Temporal averaging is also applied to the annual values in order to estimate the 15-year climatological mean values. Apart from temporal, a spatial averaging is also applied for the entire globe as well as for specific regions of interest, namely great global deserts and areas of desert dust export. According to the algorithm results, the highest frequencies of dust occurrence (up to 160 days/year) are primarily observed over the western part of North Africa (Sahara), and over the broader area of Bodélé, and secondarily over the Asian Taklamakan desert (140 days/year). For most of the study regions, the maximum frequencies appear in boreal spring and/or summer and the minimum ones in winter or autumn. A clear seasonality of global dust is revealed, with the lowest frequencies in November–December and the highest ones in June. Finally, an increasing trend of global dust frequency of occurrence from 2005 to 2019, equal to 56.2%, is also found. Such an increasing trend is observed over all study regions except for North Middle East, where a slight decreasing trend (−2.4%) is found.

Impact of High Concentrations of Saharan Dust Aerosols on Infrared-Based Land Surface Temperature Products

“…1 shows the monthly mean DuAOD corresponding to the observation-times of MSG. Dust production and transport have a clear seasonality, with higher values in the south-western region of the Sahara Desert during June-to-August, in agreement with previous studies of dust aerosol distributions in this area [46], [47]. JSTARS-2022-01719.R1…”

“…This study is performed across the area delimited by latitude circles 40°N and 10°N, and by meridians 20°W and 40°E. This domain contains the Sahara Desert, which is an optimal location to analyze the effect of dust aerosols on LST retrievals: it is a vast region with a relatively homogenous surface, largely stable over time; it is the largest source of airborne dust particles on the globe [46], [47]; the atmosphere over the desert has a relatively low water vapor content [51], which means LST retrievals over this area are less affected by this critical atmospheric component; and it has negligible amounts of other types of aerosols (such as soot, organic matter, or sea-salt) [52]. We examine the effect of dust aerosols on LST retrievals during the year 2006 and the years 2009 to 2013, to ensure overlapping with the available in situ LSTs within the area of study.…”

“…In the first part of this study (Section III-A) we compare the three LST products against the skin temperature (SKT) from ECMWF's fifth-generation climate reanalysis, ERA5, over the Sahara Desert and surrounding regions -an area of high prevalence of dust aerosols [46], [47]. ERA5's SKT corresponds to the temperature of the interface between the atmosphere's lower model layer and the soil's upper layer.…”

Quantifying Spatio-Temporal Dynamics of African Dust Detection Threshold for PM10 Concentrations in the Caribbean Area Using Multiscale Decomposition

“…It is important to recall that ICEEMDAN is the improved version of CEEMDAN (Colominas et al, 2014). For those following the seasonal cycle, the maximum values are generally between June and August, i.e., the period when the African dust sources are more active (Zuidema et al, 2019;Euphrasie-Clotilde et al, 2021;Gavrouzou et al, 2021). We must emphasize that the cases where the residue does not present seasonality are not anomalies.…”

“…The modifications of terrain properties in these source regions (vegetation cover or land use) combined with climate processes that affect them will act to modulate transport to the Caribbean area (Ginoux et al, 2012;Prospero et al, 2014). Indeed, PM 10 inter-annual variability is also connected to dust removal and deposition mechanisms (e.g., changes in precipitation) (Gavrouzou et al, 2021). Drought years in the global dust belt zone are associated with a high presence of dust in the atmosphere due to reduced wet deposition (Dey and Di Girolamo, 2010;Prospero et al, 2021).…”