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STEPHAN BORRMANN REAS THOMAS VLADIMIR RUDAKOV VLADIMIR YUSHKOV BORIS LEPUCHOV TERRY DESHLER NIKOLAI VINNICHENKO VYACHESLAV KHATTATOV LEOPOLDO STEFANUTTI 《Tellus. Series B, Chemical and physical meteorology》2000,52(4):1088-1103
In‐situ aerosol measurements were performed in the northern hemispheric stratosphere up to altitudes of 21 km between 13 November 1996 and 14 January 1997, inside and outside of the polar vortex during the Airborne Polar Experiment (APE) field campaign. These are measurements of particle size distributions with a laser optical particle counter of the FSSP‐300 type operated during 9 flights on the Russian M‐55 high‐altitude research aircraft Geophysika. For specific flights, the FSSP‐300 measurements are compared with balloon‐borne data (launched from Kiruna, Sweden). It was found that the stratospheric aerosol content reached levels well below the background concentrations measured by the NASA operated ER‐2 in 1988/89 in the northern hemisphere. During the APE campaign, no PSC particle formation was observed at flight altitudes although the temperatures were below the NAT condensation point during one flight. The measured correlations between ozone and aerosol give an indication of the subsidence inside the 1996/97 polar vortex. Despite the lower aerosol content in the winter 1996/97 compared to the 1989 background, the heterogeneous reactivity of the aerosol (as calculated from the measured data with additional model input) is comparable. This is due to the dependency of the reactive uptake coefficients on the atmospheric water vapor content. Under the described assumptions the reaction rates on the background aerosol are significantly smaller than for competing gas phase chlorine activation, as can be expected for stratospheric background conditions especially inside the polar vortex. 相似文献
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Sea foam and sea-surface films are pelagic habitats of common origin. This suggests a possible similarity between their microplanktonic assemblages and an a priori possibility to use foam samples in qualitative sea-surface film studies. The composition and abundance of microheterotrophs (nanoflagellates <5 μm and bacteria) in the Dalnezelenetskaya Inlet, Kola Peninsula, Barents Sea, in August 1987, was nearly identical in the foam and sea-surface film samples. In contrast, the enrichment of foam with autotrophs (nano- and microphytoplankton) exceeded by an order of magnitude that of sea-surface films, whereas their taxonomic compositions were virtually identical in both habitats. Elevated growth rates of phytoplankton in sea foam appear to be an ecological mechanism responsible for the enrichment. 相似文献
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JIRI CHLACHULA NIKOLAI I. DROZDOV NIKOLAI D. OVODOV 《Boreas: An International Journal of Quaternary Research》2003,32(3):506-520
Multidisciplinary Quaternary investigations in the Minusinsk Basin in the upper Yenisei River region and other southern Siberian continental depressions have produced evidence of prehistoric peopling pre‐dating the last glacial stage (>100 ka BP). Abundant ‘pebble tools’ and bone artefacts exposed from eroded alluvia of the Yenisei River terraces indicate repeated occupation of this territory since the Middle Pleistocene. A new stage of expansion of the early human occupation habitat occurred around the last interglacial (OIS 5e) by a Middle Palaeolithic (Neanderthaloid?) population characterized by a core and flake stone industry and open‐air occupation sites. The key camp/kill‐processing site at Ust‘‐Izhul’, dated to c. 125 ka BP and documenting complex behavioural activities, is so far the most complete in situ pre‐Late Palaeolithic site found in Siberia. This unique record provides new insights into the timing and the palaeoenvironmental conditions of the Pleistocene colonization of north‐central Asia. 相似文献
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