Radiative effect of aerosols above the northern and southern Atlantic Ocean as determined from shipborne lidar observations

Abstract

[1] The direct solar radiative effect of aerosols over the Atlantic Ocean was investigated on the basis of aerosol Raman/polarization lidar observations aboard the research vessel Polarstern between Germany (50 ı N) and either South America (50 ı S) or South Africa (40 ı S) in 2009 and 2010. First, a case study of complex aerosol conditions with marine aerosol, dust, and smoke particles in the boundary layer and free troposphere is presented to demonstrate that detailed knowledge of aerosol layering (boundary layer, free troposphere) and aerosol mixing state is required for an accurate determination of the resulting radiative effects. A statistical analysis based on all lidar observations revealed the highest daily mean radiative effect (-43˙59 W m -2 at the surface, -14˙18 W m -2 at top of atmosphere) in the latitudinal belt from 0 ı N-15 ı N in the Saharan dust outflow region. Mean aerosol radiative effects of the polluted northern and clean southern midlatitudes were contrasted. In the northern midlatitudes, the averaged aerosol radiative effect of all simulations was -24˙33 W m -2 at the surface which is a factor of 1.6 higher than at similar southern hemispheric latitudes. The simulations based on the lidar observations are in good agreement with colocated pyranometer measurements.

An overview of the first decade of Polly<sup>NET</sup>: an emerging network of automated Raman-polarization lidars for continuous aerosol profiling

“…This database might be a valuable tool for space-borne lidar missions like CALIPSO or the upcoming ADM-Aeolus (Atmospheric Dynamics Mission, Stoffelen et al, 2005) and EarthCARE (Earth Clouds, Aerosols and Radiation Explorer, Illingworth et al, 2015) missions. The findings may also serve for the verification of aerosol transport models (e.g., Binietoglou et al, 2015;Haustein et al, 2009) or support studies on the radiative impact of aerosol layers on the Earth's energy budget (e.g., Kanitz et al, 2013b). Thus, Polly NET can give a valuable contribution to the understanding of the complex nature of atmospheric particles which is a prerequisite to understand their complex interactions with clouds.…”

Profiling of Saharan dust from the Caribbean to western Africa – Part 1: Layering structures and optical properties from shipborne polarization/Raman lidar observations

“…1a). The containerized OCEANET-Atmosphere platform (Kanitz et al, 2011(Kanitz et al, , 2013 aboard is usually operated during north-south cruises of R/V Polarstern between Bremerhaven, Germany, and Cape Town, South Africa, or Punta Arenas, Chile.…”

Analysis of a warehouse fire smoke plume over Paris with an N<sub>2</sub> Raman lidar and an optical thickness matching algorithm

“…The molecular extinction (α mol ) and backscatter (β mol ) coefficients can be calculated from climatological air mass models or radiosonde measurements. They are determined in this study with a polynomial approximation as in Nicolet (1984) using a reference atmospheric density calculated from ancillary measurements (Chazette et al, 2010); β mol λ E is expressed as 3k f α mol λ E /8π , with the King factor of air k f (King, 1923). The aerosol extinction (α aer ) is assumed to be proportional to λ −Å , where the Ångström exponent Å (Ångström, 1964) is considered to be a constant depending on the aerosol nature.…”