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Author: Ansmann, Albert × Subject: anthropogenic source ×

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    Profiling of Saharan dust from the Caribbean to western Africa - Part 2: Shipborne lidar measurements versus forecasts
    (Katlenburg-Lindau : EGU, 2017) Ansmann, Albert; Rittmeister, Franziska; Engelmann, Ronny; Basart, Sara; Jorba, Oriol; Spyrou, Christos; Remy, Samuel; Skupin, Annett; Baars, Holger; Seifert, Patric; Senf, Fabian; Kanitz, Thomas
    A unique 4-week ship cruise from Guadeloupe to Cabo Verde in April-May 2013 see part 1, Rittmeister et al. (2017) is used for an in-depth comparison of dust profiles observed with a polarization/Raman lidar aboard the German research vessel Meteor over the remote tropical Atlantic and respective dust forecasts of a regional (SKIRON) and two global atmospheric (dust) transport models (NMMB/BSC-Dust, MACC/CAMS). New options of model-observation comparisons are presented. We analyze how well the modeled fine dust (submicrometer particles) and coarse dust contributions to light extinction and mass concentration match respective lidar observations, and to what extent models, adjusted to aerosol optical thickness observations, are able to reproduce the observed layering and mixing of dust and non-dust (mostly marine) aerosol components over the remote tropical Atlantic. Based on the coherent set of dust profiles at well-defined distances from Africa (without any disturbance by anthropogenic aerosol sources over the ocean), we investigate how accurately the models handle dust removal at distances of 1500g km to more than 5000g km west of the Saharan dust source regions. It was found that (a) dust predictions are of acceptable quality for the first several days after dust emission up to 2000g km west of the African continent, (b) the removal of dust from the atmosphere is too strong for large transport paths in the global models, and (c) the simulated fine-to-coarse dust ratio (in terms of mass concentration and light extinction) is too high in the models compared to the observations. This deviation occurs initially close to the dust sources and then increases with distance from Africa and thus points to an overestimation of fine dust emission in the models.
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    Potential of polarization/Raman lidar to separate fine dust, coarse dust, maritime, and anthropogenic aerosol profiles
    (München : European Geopyhsical Union, 2017) Mamouri, Rodanthi-Elisavet; Ansmann, Albert
    We applied the recently introduced polarization lidar–photometer networking (POLIPHON) technique for the first time to triple-wavelength polarization lidar measurements at 355, 532, and 1064 nm. The lidar observations were performed at Barbados during the Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in the summer of 2014. The POLIPHON method comprises the traditional lidar technique to separate mineral dust and non-dust backscatter contributions and the new, extended approach to separate even the fine and coarse dust backscatter fractions. We show that the traditional and the advanced method are compatible and lead to a consistent set of dust and non-dust profiles at simplified, less complex aerosol layering and mixing conditions as is the case over the remote tropical Atlantic. To derive dust mass concentration profiles from the lidar observations, trustworthy extinction-to-volume conversion factors for fine, coarse, and total dust are needed and obtained from an updated, extended Aerosol Robotic Network sun photometer data analysis of the correlation between the fine, coarse and total dust volume concentration and the respective fine, coarse, and total dust extinction coefficient for all three laser wavelengths. Conversion factors (total volume to extinction) for pure marine aerosol conditions and continental anthropogenic aerosol situations are presented in addition. As a new feature of the POLIPHON data analysis, the Raman lidar method for particle extinction profiling is used to identify the aerosol type (marine or anthropogenic) of the non-dust aerosol fraction. The full POLIPHON methodology was successfully applied to a SALTRACE case and the results are discussed. We conclude that the 532 nm polarization lidar technique has many advantages in comparison to 355 and 1064 nm polarization lidar approaches and leads to the most robust and accurate POLIPHON products.