Satellite and surface-based remote sensing of Saharan dust aerosols

In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: a b s t r a c t a r t i c l e i n f o The spatial and temporal characteristics of dust aerosols and their properties are assessed from satellite and ground-based sensors. The spatial distribution of total column aerosol optical depth at 550 nm (AOD) from the Moderate Resolution Imaging SpectroRadiometer (MODIS) coupled with top of atmosphere Clouds and the Earth's Radiant Energy System (CERES) shortwave fluxes are examined from the Terra satellite over the Atlantic Ocean. These data are then compared with AOD from two Aerosol Robotic Network (AERONET) ground-based sun photometer measurement sites for nearly six years (2000–2005). These two sites include Capo Verde (CV) (16°N, 24°W) near the Saharan dust source region and La Paguera (LP) (18°N, 67°W) that is downwind of the dust source regions. The AOD is two to three times higher during spring and summer months over CV when compared to LP and the surrounding regions. For a unit AOD value, the instantaneous TOA shortwave direct radiative effect (DRE) defined as the change in shortwave flux between clear and aerosol skies for CV and LP are − 53 and − 68 Wm − 2 respectively. DRE for LP is likely more negative due to fall out of larger particles during transport from CV to LP. However, separating the CERES-derived DRE by MODIS aerosol effective radii was difficult. Satellite and ground-based dust aerosol data sets continue to be useful to understand dust processes related to the surface and the atmosphere. The Sahara is the largest source of windblown dust aerosols (Prospero et al., 2002) and accounts for nearly 50% of dust supplied to the oceans (Miller et al., 2004). During the April–October months over the Saharan desert, northeasterly trade winds have sufficient wind speeds to dislodge sediments from the ground to the atmosphere (Koren & Kaufman, 2004). While the Bodele (∼17°N, 18°E) in Chad is the largest source of dust aerosols in the Sahara, other sources in Western Africa include areas in Mali, Mauritania, and Algeria (Goudie & Middleton, 2001). However, the source strength of dust aerosols has been difficult to estimate with values ranging from 100–1500 million tons per …