Abstract
AbstractAirborne lidar observations of long‐range transported Saharan air layers in the western North Atlantic trades indicate increased amounts of water vapor within the dust layers compared to the surrounding dry free atmosphere. This study investigates the impact of such enhanced water vapor concentrations on radiative heating. Therefore, spatially high resolved airborne high spectral resolution and differential absorption lidar measurements are used for the parametrization of aerosol optical properties and water vapor concentrations in radiative transfer calculations. Heating rates that are calculated under consideration of the measured water vapor distribution strongly differ from heating rates that are derived under assumption of an atmospheric reference water vapor profile which is steadily decreasing with altitude. Results highlight that water vapor represents a major radiative driver for dust layer vertical mixing and the maintenance of bounding inversions at the top and bottom of the dust layer.
Highlights
Aeolian mineral dust is one of the major contributors to the global tropospheric aerosol load (d’Almeida et al, 1991; Kinne et al, 2006) and is known to play a key role in the Earth's climate system (Satheesh and Moorthy, 2005)
Heating rates that are calculated under consideration of the measured water vapor distribution strongly differ from heating rates that are derived under assumption of an atmospheric reference water vapor profile which is steadily decreasing with altitude
Enhanced Concentrations of Water Vapor in Saharan air layer (SAL) Within the framework of NARVAL-II a total of four research flights (16 flight hours) were designed to lead over regions comprising long-range transported SALs. During all of those flights, WALES lidar measurements showed enhanced concentrations of water vapor inside SALs compared to the surrounding dry free troposphere
Summary
Aeolian mineral dust is one of the major contributors to the global tropospheric aerosol load (d’Almeida et al, 1991; Kinne et al, 2006) and is known to play a key role in the Earth's climate system (Satheesh and Moorthy, 2005). It impacts the atmosphere's radiation budget by scattering, absorbing, and emitting radiation and by acting as nucleus for ice and water droplet formation (Boose et al, 2016; Karydis et al, 2011). Studies with focus on Saharan dust radiative effects and heating rates rather concentrated on source regions and areas at the origin of dust transport (Kanitz et al, 2013; Li et al, 2004; Mallet et al, 2009; Zhu et al, 2007) and profound understanding on radiative transfer in long-range transported
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