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By BERND HEINOLD INA TEGEN MICHAEL ESSELBORN KONRAD KANDLER PETER KNIPPERTZ DETLEF MÜLLER ALEXANDER SCHLADITZ MATTHIAS TESCHE BERNADETT WEINZIERL ALBERT ANSMANN DIETRICH ALTHAUSEN BENOIT LAURENT REAS MASSLING THOMAS MÜLLER REAS PETZOLD KERSTIN SCHEPANSKI ALFRED WIEDENSOHLER 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):307-324
The regional dust model system LM-MUSCAT-DES was developed in the framework of the SAMUM project. Using the unique comprehensive data set of near-source dust properties during the 2006 SAMUM field campaign, the performance of the model system is evaluated for two time periods in May and June 2006. Dust optical thicknesses, number size distributions and the position of the maximum dust extinction in the vertical profiles agree well with the observations. However, the spatio-temporal evolution of the dust plumes is not always reproduced due to inaccuracies in the dust source placement by the model. While simulated winds and dust distributions are well matched for dust events caused by dry synoptic-scale dynamics, they are often misrepresented when dust emissions are caused by moist convection or influenced by small-scale topography that is not resolved by the model. In contrast to long-range dust transport, in the vicinity of source regions the model performance strongly depends on the correct prediction of the exact location of sources. Insufficiently resolved vertical grid spacing causes the absence of inversions in the model vertical profiles and likely explains the absence of the observed sharply defined dust layers. 相似文献
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Dust mobilization and transport in the northern Sahara during SAMUM 2006 – a meteorological overview
By PETER KNIPPERTZ ALBERT ANSMANN DIETRICH ALTHAUSEN DETLEF MÜLLER MATTHIAS TESCHE EIKE BIERWIRTH TILMAN DINTER THOMAS MÜLLER WOLFGANG VON HOYNINGEN-HUENE KERSTIN SCHEPANSKI MANFRED WENDISCH BERND HEINOLD KONRAD KANDLER REAS PETZOLD LOTHAR SCHÜTZ INA TEGEN 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):12-31
The SAMUM field campaign in southern Morocco in May/June 2006 provides valuable data to study the emission, and the horizontal and vertical transports of mineral dust in the Northern Sahara. Radiosonde and lidar observations show differential advection of air masses with different characteristics during stable nighttime conditions and up to 5-km deep vertical mixing in the strongly convective boundary layer during the day. Lagrangian and synoptic analyses of selected dust periods point to a topographic channel from western Tunisia to central Algeria as a dust source region. Significant emission events are related to cold surges from the Mediterranean in association with eastward passing upper-level waves and lee cyclogeneses south of the Atlas Mountains. Other relevant events are local emissions under a distinct cut-off low over northwestern Africa and gust fronts associated with dry thunderstorms over the Malian and Algerian Sahara. The latter are badly represented in analyses from the European Centre for Medium–Range Weather Forecasts and in a regional dust model, most likely due to problems with moist convective dynamics and a lack of observations in this region. This aspect needs further study. The meteorological source identification is consistent with estimates of optical and mineralogical properties of dust samples. 相似文献
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FRANK WAGNER DANIELE BORTOLI SÉRGIO PEREIRA MARIA JOÃO COSTA ANA MARIA SILVA BERNADETT WEINZIERL MICHAEL ESSELBORN REAS PETZOLD KATHI RASP BERND HEINOLD INA TEGEN 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):297-306
Aerosol properties of mineral particles in the far field of an African desert dust outbreak were investigated that brought Saharan dust over the Mediterranean in different layers to Portugal. The measurements were performed inside the project Desert Aerosols over Portugal (DARPO) which was linked to the Saharan Mineral Dust Experiment (SAMUM). The maximum particle mass concentration was about 150 μg m−3 and the corresponding scattering coefficient was 130 M m−1 which results in a mass scattering efficiency of 0.87 m2 g−1 . The aerosol optical depth reached values up to 0.53 and the lidar ratio was between 45 and 50 in the whole dust loaded column. A comparison between particle size distributions and refractive indices derived from different instruments and models showed a general good agreement but some minor differences could also be observed. Measurements as well as calculations with a particle transport model suggest that there is a relatively higher concentration of very large particles in the upper region of the dust layer than on the surface which is likely connected with meteorological conditions at the observational site (Évora, Portugal). 相似文献
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By MATTHIAS TESCHE ALBERT ANSMANN DETLEF MÜLLER DIETRICH ALTHAUSEN INA MATTIS BIRGIT HEESE VOLKER FREUDENTHALER MATTHIAS WIEGNER MICHAEL ESSELBORN GIANLUCA PISANI PETER KNIPPERTZ 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):144-164
Three ground-based Raman lidars and an airborne high-spectral-resolution lidar (HSRL) were operated during SAMUM 2006 in southern Morocco to measure height profiles of the volume extinction coefficient, the extinction-to-backscatter ratio and the depolarization ratio of dust particles in the Saharan dust layer at several wavelengths. Aerosol Robotic Network (AERONET) Sun photometer observations and radiosoundings of meteorological parameters complemented the ground-based activities at the SAMUM station of Ouarzazate. Four case studies are presented. Two case studies deal with the comparison of observations of the three ground-based lidars during a heavy dust outbreak and of the ground-based lidars with the airborne lidar. Two further cases show profile observations during satellite overpasses on 19 May and 4 June 2006. The height resolved statistical analysis reveals that the dust layer top typically reaches 4–6 km height above sea level (a.s.l.), sometimes even 7 km a.s.l.. Usually, a vertically inhomogeneous dust plume with internal dust layers was observed in the morning before the evolution of the boundary layer started. The Saharan dust layer was well mixed in the early evening. The 500 nm dust optical depth ranged from 0.2–0.8 at the field site south of the High Atlas mountains, Ångström exponents derived from photometer and lidar data were between 0–0.4. The volume extinction coefficients (355, 532 nm) varied from 30–300 Mm−1 with a mean value of 100 Mm−1 in the lowest 4 km a.s.l.. On average, extinction-to-backscatter ratios of 53–55 sr (±7–13 sr) were obtained at 355, 532 and 1064 nm. 相似文献
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