ON THE SENSITIVITY OF PRECIPITATION FORECASTS TO THE MOIST PHYSICS AND THE HORIZONTAL RESOLUTION OF NUMERICAL MODEL     

俞小鼎  Leif Laursen  Erik Rasmussen 《Acta Meteorologica Sinica》1997,(4)

The impacts of the enhanced model's moist physics and horizontal resolution upon the QPFs(quantitative precipitation forecasts)are investigated by applying the HIRLAM(high resolutionlimited area model)to the summer heavy-rain cases in China.The performance of the control run,for which a 0.5°×0.5°grid spacing and a traditional“grid-box supersaturation removal+Kuo typeconvective paramerization”are used as the moist physics,is compared with that of the sensitivityruns with an enhanced model's moist physics(Sundqvist scheme)and an increased horizontalresolution(0.25°×0.25°),respectively.The results show:(1)The enhanced moist physics scheme(Sundqvist scheme),by introducing the cloud watercontent as an additional prognostic variable and taking into account briefly of the microphysicsinvolved in the cloud-rain conversion,does bring improvements in the model's QPFs.Althoughthe deteriorated QPFs also occur occasionally,the improvements are found in the majority of thecases,indicating the great potential for the improvement of QPFs by enhancing the model's moistphysics.(2)By increasing the model's horizontal resolution from 0.5°×0.5°,which is already quitehigh compared with that of the conventional atmospheric soundings,to 0.25°×0.25°without thesimultaneous enhancement in model physics and objective analysis,the improvements in QPFs arevery limited.With higher resolution,although slight amelioration in locating the rainfall centersand in resolving some finer structures of precipitation pattern are made,the number of the mis-predicted fine structures in rainfall field increases with the enhanced model resolution as well.  相似文献   

Sediment pollution in the Vågen,Bergen harbour,Norway     

Matthias Paetzel  Geir Nes  Leif Leifsen  Hans Schrader 《Environmental Geology》2003,43(4):476-483

Recent sediments in the Vågen, Bergen harbour, are subjected to injection of untreated sewage from around 15,000 person equivalent. Here the distribution of trace elements is mapped in surface and subsurface sediments. Selected trace-element concentrations decrease from the inner towards the outer Vågen. These concentration gradients do not correlate with minerogenic grain size. Linear correlation, combined with enriched sediment trace elements, are used to infer sources for these elements and possible reasons for their enrichment. (1) Frequent use of dental amalgam might be related to the enrichments of and correlation between Ag, Cu, Hg and Sn in surficial sediments pre-1994. (2) Enrichment and correlation of Cu/Zn may be related to the commercial and private use of anti-fouling boat-paint. Further, tributyltin is suggested as a source of Sn enrichment. (3) Increased traffic in the city of Bergen with gasoline combustion and car-wheel wear-off release Pb and Zn. (4) Hg and Pb might have been atmospherically supplied due to the combustion of coal in a nearby gas plant pre-1985. (5) No correlation is observed between enriched Vågen trace metals and bedrock element composition of the surrounding mountains, indicating a minor supply from erosion.  相似文献   

Sources to the East Greenland Current and its contribution to the Denmark Strait Overflow     

Emil Jeansson  Sara Jutterström  Leif G. Anderson  E. Peter Jones  James H. Swift 《Progress in Oceanography》2008,78(1):12-28

Data from the East Greenland Current in 2002 are evaluated using optimum multiparameter analysis. The current is followed from north of Fram Strait to the Denmark Strait Sill and the contributions of different source waters, in mass fractions, are deduced. From the results it can be concluded that, at least in spring 2002, the East Greenland Current was the main source for the waters found at the Denmark Strait Sill, contributing to the overflow into the North Atlantic. The East Greenland Current carried water masses from different source regions in the Arctic Ocean, the West Spitsbergen Current and the Greenland Sea. The results agree well with the known circulation of the western Nordic Seas but also add knowledge both to the quantification and to the mixing processes, showing the importance of the locally formed Greenland Sea Arctic Intermediate Water for the East Greenland Current and the Denmark Strait.  相似文献   

Long term evolution of solar sector structure     

Leif Svalgaard  John M. Wilcox 《Solar physics》1975,41(2):461-475

The large-scale structure of the solar magnetic field during the past five sunspot cycles (representing by implication a much longer interval of time) has been investigated using the polarity (toward or away from the Sun) of the interplanetary magnetic field as inferred from polar geomagnetic observations. The polarity of the interplanetary magnetic field has previously been shown to be closely related to the polarity (into or out of the Sun) of the large-scale solar magnetic field. It appears that a solar structure with four sectors per rotation persisted through the past five sunspot cycles with a synodic rotation period near 27.0 days, and a small relative westward drift during the first half of each sunspot cycle and a relative eastward drift during the second half of each cycle. Superposed on this four-sector structure there is another structure with inward field polarity, a width in solar longitude of about 100° and a synodic rotation period of about 28 to 29 days. This 28.5 day structure is usually most prominent during a few years near sunspot maximum. Some preliminary comparisons of these observed solar structures with theoretical considerations are given.  相似文献   

Modelling the potential impact of global warming on Ips typographus voltinism and reproductive diapause     

Anna Maria Jönsson  Susanne Harding  Paal Krokene  Holger Lange  Åke Lindelöw  Bjørn Økland  Hans Peter Ravn  Leif Martin Schroeder 《Climatic change》2011,109(3-4):695-718

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Environmental toxicology: population modeling of cod larvae shows high sensitivity to loss of zooplankton prey     

Stige LC  Ottersen G  Hjermann DØ  Dalpadado P  Jensen LK  Stenseth NC 《Marine pollution bulletin》2011,62(2):395-398

Two factors determine whether pollution is likely to affect a population indirectly through loss of prey: firstly, the sensitivity of the prey to the pollutants, and secondly, the sensitivity of the predator population to loss of prey at the given life stage. We here apply a statistical recruitment model for Northeast Arctic cod to evaluate the sensitivity of cod cohorts to loss of zooplankton prey, for example following an oil spill. The calculations show that cod cohorts are highly sensitive to possible zooplankton biomass reductions in the distribution area of the cod larvae, and point to a need for more knowledge about oil-effects on zooplankton. Our study illustrates how knowledge about population dynamics may guide which indirect effects to consider in environmental impact studies.  相似文献   

Follow-up Ephemerides and the Accuracy of Preliminary Orbits     

Leif Kahl Kristensen 《Icarus》2002,159(2):339-350

The accuracy of follow-up ephemerides and orbits of asteroids based on a short arc is investigated. The geocentric distance and its time derivative are the essential parameters determining the accuracy of predicted positions. The consequences for the optimal observing strategies are discussed. The node and inclination of the orbital plane are restricted enough to be useful for a preliminary sorting of candidates for linking.  相似文献   

Magnetic field in the intracluster medium: Rydberg matter with almost free electrons     

Shahriar Badiei  Leif Holmlid 《Monthly notices of the Royal Astronomical Society》2002,335(4):L94-L98

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The alkali metal atmospheres on the Moon and Mercury: Explaining the stable exospheres by heavy Rydberg Matter clusters     

Leif Holmlid 《Planetary and Space Science》2006,54(1):101-112

Despite recent progress in the modeling of alkali atmospheres like those around the Moon and Mercury, many problems still exist. It is proposed that Rydberg Matter (RM) clusters containing Na and K atoms are the main part of the alkali atmospheres of the Moon and Mercury, forming large clouds. RM clusters are studied in the laboratory with laser fragmentation and laser spectroscopy methods. Due to the very large collision cross sections of Rydberg atoms and RM clusters, the atmospheres are not collision free, as normally assumed based on the low densities of free alkali atoms. The non-escaping radial density variation for the Na atoms, observed, e.g., on the Moon, and the Maxwellian velocity distributions observed on Mercury are caused by a true atmosphere with collisional equilibration; this process is not possible in an exosphere. Fast alkali atoms are released from the RM clusters already at large heights by solar photons and charged particle impact. The kinetic temperatures derived for the atmospheres agree with the quantized energy release. The cluster model predicts that the rate of loss from the surface is much smaller than for a purely atomic model, since the transient storage is in the RM cluster form in the atmosphere and not at the surface. The conductance of the atmosphere is of the order of 100 S due to the facile collisional ionization of the RM clusters. The apparent depletion of K in the atmosphere of Mercury is explained.  相似文献   

A letter to the Subcommission for European Quaternary Stratigraphy     

Svend Th. Andersen Chariman  Leif Aabo Rasmussen Secretary 《Boreas: An International Journal of Quaternary Research》1980,9(4):250-250

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