Do stratocumulus clouds detrain? FIRE I data revisited     

Stephan R. de Roode  Qing Wang 《Boundary-Layer Meteorology》2007,122(2):479-491

Analyses of aircraft observations of the stratocumulus-topped boundary layer during the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE I) show the frequent presence of clear, but relatively moist, air patches near the stratocumulus cloud-top interface. A conditional sampling of measurements in these clear air patches shows that their thermodynamic properties do more resemble boundary-layer air characteristics than those of free troposphere air. From an aircraft leg through cloud tops it is demonstrated that turbulent mixing across the cloud-top interface can lead to the local dissipation of the cloud top. Analogous to the terminology used for shallow cumulus parameterizations this process can be considered as detrainment, with which we mean that after a mixing event across the cloud-top boundaries, mixed unsaturated parcels become part of the clear environment of the cloud.  相似文献   

Detailed observational study of a weak Echo region     

Stephan P. Nelson  Roscoe R. Braham Jr. 《Pure and Applied Geophysics》1975,113(1):735-746

High resolution 3-cm weather radar was used to observe the three dimensional structure of a weak echo region of a severe convective storm in northern Minnesota, U.S.A. Observations show that a seemingly steady-state updraft in the lower portion of the storm broke into an unsteady structure in the upper levels. This is interpreted as indicating that precipitation loading gradually decelerated the upper reaches of the updraft, resulting in periodic breakout of a new updraft core on the inflow side. This periodic behavior of the updraft may be related to hailstreaks and what has been termed the multi-celled storm.  相似文献   

Sea level induced variations in clay mineral composition in the southwestern South China Sea over the past 17,000 yr     

Stephan Steinke  Till J.J. Hanebuth  Christoph Vogt  Karl Stattegger 《Marine Geology》2008,250(3-4):199-210

Variations in clay mineral composition of sediment cores from the margin and continental slope of the Sunda Shelf (southern South China Sea, SE Asia) covering the past 17,000 yr reflect changing influences of sediment sources together with clay mineral partitioning processes in shallow waters. We identify the deglacial sea level rise as the principal factor driving these changes. During the late glacial, high values of kaolinite are interpreted to reflect a higher contribution of clays from soils that have formed on the exposed Sunda Shelf and in the southern archipelagos of Indonesia. At this time core sites were located in close proximity to the mouths of the Sunda Shelf palaeo-drainage systems on the emerged shelf (“Sundaland”). The progressive landward displacement of the coastline and breakdown of these vast drainage systems during deglaciation led to a decrease in influence of the kaolinite-rich southern sources. When the coastline had retreated closely to its present-day position in mid-Holocene times, the former dominance of southern sources was replaced by a stronger influence of illite-rich sources (e.g. Borneo). The overriding control of sea level changes on the clay mineral distribution patterns precludes a definite climatic interpretation of clay mineral data in terms of climatic/monsoonal changes in such highly dynamic sedimentary environment.  相似文献   

Evidence for enhanced hydration on the northern flank of Olympus Mons, Mars     

Giancarlo Bellucci  Joern Helbert  Francesca Altieri  Dennis Reiss  Jean-Pierre Bibring  Stephan van Gasselt  Harald Hoffmann  Yves Langevin  Gerhard Neukum  Franois Poulet 《Icarus》2007,192(2):361-377

In this paper we report about a small region on the northern scarp of Olympus Mons showing an increase of the 3 μm hydration band in the OMEGA spectra, together with low superficial temperatures. Although water ice clouds can occurs on the flank of big martian volcanoes, radiative transfer modeling indicates that atmospheric water ice alone cannot justify the shape of the observed band. A fit of the 1.9–3 μm absorption features is obtained by hypothesizing that the study region consists of a mixture of dust and water ice covered by an optically thin (τ=0.08 at 3 μm) layer of dust. Thermal modeling also suggests that water ice in this region may be stable during most of the martian year due to the saturation of the atmosphere. If water ice is responsible for the observed spectral behavior, it might consist of a number of ice or snow patches possibly deposited in small depressions.  相似文献   

Technologies for adaptation to climate change. Examples from the agricultural and water sectors in Lebanon     

Sara Trærup  Jean Stephan 《Climatic change》2015,131(3):435-449

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