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By RALPH KAHN REAS PETZOLD MANFRED WENDISCH EIKE BIERWIRTH TILMAN DINTER MICHAEL ESSELBORN MARCUS FIEBIG BIRGIT HEESE PETER KNIPPERTZ DETLEF MÜLLER ALEXANDER SCHLADITZ WOLFGANG VON HOYNINGEN-HUENE 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):239-251
Coincident observations made over the Moroccan desert during the Sahara mineral dust experiment (SAMUM) 2006 field campaign are used both to validate aerosol amount and type retrieved from multi-angle imaging spectroradiometer (MISR) observations, and to place the suborbital aerosol measurements into the satellite's larger regional context. On three moderately dusty days during which coincident observations were made, MISR mid-visible aerosol optical thickness (AOT) agrees with field measurements point-by-point to within 0.05–0.1. This is about as well as can be expected given spatial sampling differences; the space-based observations capture AOT trends and variability over an extended region. The field data also validate MISR's ability to distinguish and to map aerosol air masses, from the combination of retrieved constraints on particle size, shape and single-scattering albedo. For the three study days, the satellite observations (1) highlight regional gradients in the mix of dust and background spherical particles, (2) identify a dust plume most likely part of a density flow and (3) show an aerosol air mass containing a higher proportion of small, spherical particles than the surroundings, that appears to be aerosol pollution transported from several thousand kilometres away. 相似文献
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STEFAN LAUTERBACH ACHIM BRAUER NILS ANDERSEN DAN L. DANIELOPOL PETER DULSKI MATTHIAS HÜLS KRYSTYNA MILECKA TADEUSZ NAMIOTKO BIRGIT PLESSEN ULRICH VON GRAFENSTEIN DECLAKES PARTICIPANTS 《Boreas: An International Journal of Quaternary Research》2011,40(1):57-72
Lauterbach, S., Brauer, A., Andersen, N., Danielopol, D. L., Dulski, P., Hüls, M., Milecka, K., Namiotko, T., Plessen, B., von Grafenstein, U. & DecLakes participants 2010: Multi‐proxy evidence for early to mid‐Holocene environmental and climatic changes in northeastern Poland. Boreas, 10.1111/j.1502‐3885.2010.00159.x. ISSN 0300‐9483. We investigated the sedimentary record of Lake Hańcza (northeastern Poland) using a multi‐proxy approach, focusing on early to mid‐Holocene climatic and environmental changes. AMS 14C dating of terrestrial macrofossils and sedimentation rate estimates from occasional varve thickness measurements were used to establish a chronology. The onset of the Holocene at c. 11 600 cal. a BP is marked by the decline of Lateglacial shrub vegetation and a shift from clastic‐detrital deposition to an autochthonous sedimentation dominated by biochemical calcite precipitation. Between 10 000 and 9000 cal. a BP, a further environmental and climatic improvement is indicated by the spread of deciduous forests, an increase in lake organic matter and a 1.7‰ rise in the oxygen isotope ratios of both endogenic calcite and ostracod valves. Rising δ18O values were probably caused by a combination of hydrological and climatic factors. The persistence of relatively cold and dry climate conditions in northeastern Poland during the first one and a half millennia of the Holocene could be related to a regional eastern European atmospheric circulation pattern. Prevailing anticyclonic circulation linked to a high‐pressure cell above the retreating Scandinavian Ice Sheet might have blocked the influence of warm and moist Westerlies and attenuated the early Holocene climatic amelioration in the Lake Hańcza region until the final decay of the ice sheet. 相似文献
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HANNE BIRGIT MADSEN KAREN LUISE KNUDSEN 《Boreas: An International Journal of Quaternary Research》1994,23(4):495-504
A study of sea-bottom samples from shallow waters in the northern part of Scoresby Sund, off Jameson Land, East Greenland, reveals four different foraminiferal assemblages between 1.3 and 35.6 m water depth. The shallowest samples. Assemblage SA (1.3–2.2 m), contain only very few foraminifera, presumably due to the annual repeated formation of an ice foot. Assemblage SB (3.7 and 4.3 m) is characterized by the calcareous species Haynesina nivea and H. orbiculare , while the arenaceous species Spiropleclammina biformis, Reophax arctica , and Recurvoides turbinatus dominate all the faunas of Assemblage SC (9.3–25.9 m depth). The change in fauna to the succeeding Portatrochammina bipolaris - Spiropleclammina biformis fauna (Assemblage SD, 29.6 and 35.6 m) presumably corresponds to the transition from the shallow Fjord water layer to the deeper and relatively more stable Polar water. Elphidiella hannai (Cushman & Grant) is recorded live for the first time in recent assemblages from the Atlantic Ocean. 相似文献
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By EIKE BIERWIRTH MANFRED WENDISCH RÉ EHRLICH BIRGIT HEESE MATTHIAS TESCHE DIETRICH ALTHAUSEN ALEXANDER SCHLADITZ DETLEF MÜLLER SEBASTIAN OTTO THOMAS TRAUTMANN TILMAN DINTER WOLFGANG von HOYNINGEN-HUENE RALPH KAHN ‡ 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):252-269
In May–June 2006, airborne and ground-based solar (0.3–2.2 μm) and thermal infrared (4–42 μm) radiation measurements have been performed in Morocco within the Saharan Mineral Dust Experiment (SAMUM). Upwelling and downwelling solar irradiances have been measured using the Spectral Modular Airborne Radiation Measurement System (SMART)-Albedometer. With these data, the areal spectral surface albedo for typical surface types in southeastern Morocco was derived from airborne measurements for the first time. The results are compared to the surface albedo retrieved from collocated satellite measurements, and partly considerable deviations are observed. Using measured surface and atmospheric properties, the spectral and broad-band dust radiative forcing at top-of-atmosphere (TOA) and at the surface has been estimated. The impact of the surface albedo on the solar radiative forcing of Saharan dust is quantified. In the SAMUM case of 19 May 2006, TOA solar radiative forcing varies by 12 W m−2 per 0.1 surface-albedo change. For the thermal infrared component, values of up to +22 W m−2 were derived. The net (solar plus thermal infrared) TOA radiative forcing varies between −19 and +24 W m−2 for a broad-band solar surface albedo of 0.0 and 0.32, respectively. Over the bright surface of southeastern Morocco, the Saharan dust always has a net warming effect. 相似文献