共查询到20条相似文献，搜索用时 31 毫秒
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The new MOdèle de Chimie Atmosphérique à Grande Echelle (MOCAGE) three-dimensional multiscale chemistry and transport model (CTM) has been applied to study heavy pollution episodes observed during the ESCOMPTE experiment. The model considers the troposphere and lower stratosphere, and allows the possibility of zooming from the planetary scale down to the regional scale over limited area subdomains. Like this, it generates its own time-dependent chemical boundary conditions in the vertical and in the horizontal. This paper focuses on the evaluation and quantification of uncertainties related to chemical and transport modelling during two intensive observing periods, IOP2 and IOP4 (June 20–26 and July 10–14, 2001, respectively). Simulations are compared to the database of four-dimensional observations, which includes ground-based sites and aircraft measurements, radiosoundings, and quasi-continuous measurements of ozone by LIDARs. Thereby, the observed and modelled day-to-day variabilities in air composition both at the surface and in the vertical have been assessed. Then, three sensitivity studies are conducted concerning boundary conditions, accuracy of the emission dataset, and representation of chemistry. Firstly, to go further in the analysis of chemical boundary conditions, results from the standard grid nesting set-up and altered configurations, relying on climatologies, are compared. Along with other recent studies, this work advocates the systematic coupling of limited-area models with global CTMs, even for regional air quality studies or forecasts. Next, we evaluate the benefits of using the detailed high-resolution emissions inventory of ESCOMPTE: improvements are noticeable both on ozone reactivity and on the concentrations of various species of the ozone photochemical cycle especially primary ones. Finally, we provide some insights on the comparison of two simulations differing only by the parameterisation of chemistry and using two state-of-the-art chemical schemes for regional photochemical modelling. Regional air quality modelling is found to be highly sensitive to the emission inventory dataset and also to the vertical and horizontal boundary conditions and detailed representation of chemistry. Interestingly enough, they infer the same range of errors compared to total model errors. 相似文献
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R. F. Pueschel D. A. Allen C. Black S. Faisant G. V. Ferry S. D. Howard J. M. Livingston J. Redemann C. E. Sorenson S. Verma 《Atmospheric Research》1995,38(1-4)
On February 8, 1993, the NASA DC-8 aircraft profiled from 10,000 to 37,000 feet (3.1–11.3 km) pressure altitude in a stratified section of tropical cyclone “Oliver” over the Coral Sea northeast of Australia. Size, shape and phase of cloud and precipitation particles were measured with a 2-D Greyscale probe. Cloud/ precipitation particles changed from liquid to ice as soon as the freezing level was reached near 17,000 feet (5.2 km) pressure altitude. The cloud was completely glaciated at −5°C. There was no correlation between ice particle habit and ambient temperature. In the liquid phase, the precipitation-cloud drop concentration was 4.0 × 103 m−3, the geometric mean diameter Dg=0.5−0.7 mm, and the liquid water content 0.7−1.9 g m−3. The largest particles anywhere in the cloud, dominated by fused dendrites at concentrations similar to that of raindrops (2.5 × 103 m−3) but a higher condensed water content (5.4 g m−3 estimated) were found in the mixed phase; condensed water is removed very effectively from the mixed layer due to high settling velocities of the large mixed particles. The highest number concentration (4.9 × 104 m−3), smallest size (Dg=0.3−0.4 mm), largest surface area (up to 2.6 × 102 cm2 m−3 at 0.4−1.0 g m−3 of condensate) existed in the ice phase at the coldest temperature (−40°C) at 35,000 feet (10.7 km). Each cloud contained aerosol (haze particles) in addition to cloud particles. The aerosol total surface area exceeded that of the cirrus particles at the coldest temperature. Thus, aerosols must play a significant role in the upscattering of solar radiation. Light extinction (6.2 km−1) and backscatter (0.8 sr−1 km−1) was highest in the coldest portion of the cirrus cloud at the highest altitude. 相似文献
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An acoustic Doppler sounder has been used to document the behaviour of the stable atmospheric boundary layer during the “Coast” experiment, in April-May, 1983, on a homogeneous terrain near the Dutch coast. It has been shown that kaimal's model of the spectrum of velocity in the stable surface layer can be applied and that surface-layer parameterization can be used in the whole stable surface layer. Velocity spectra have been computed between .0005 c.p.s. and .1 c.p.s. and for the stability range for z/L between 0 and 10. It is to be noted that the information has been obtained using only sodar data. 相似文献
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Transport safety is a major goal in the European Union. Low visibility conditions, especially due to fog, increase the risk of major accidents (chain collision). Innovative products have been developed by the automotive industry, including equipment manufacturers, to increase the level of safety of car passengers and drivers. Testing of these products requires the simulation or artificial reproduction of low visibility (fog) conditions with good stability and reproducibility characteristics. We report on the results of the European Union funded “FOG” project to improve road transport safety through fog production in an experimental test chamber located at the Clermont-Ferrand laboratory for research on road safety and visibility. The project developed a prototype of a small-scale climatic chamber, an improved fog production spraying device, a laser-based visibility measurement device, a reduced scale transmissometer, and a combined indoor climate-fog production simulation software. The ability of the fog chamber to test for driver reaction was also investigated. Recent developments include a device able to produce stable visibility levels and homogeneous fog, representative of various types of natural water droplet distribution. The fog characteristics were determined and compared to natural fog. Results are presented for a selection of conditions including stabilized visibility levels for dense fog and two kinds of droplet distributions. 相似文献
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The human dimensions of global change research community includes scholars in the natural and social sciences working in universities and government laboratories who share common interests and who communicate with each other through journals, workshops, and conferences and via the Internet. Information and communication technologies, in particular, e-mail, listservs, and the WWW, where speed and low cost are key features, from the backbone of an “electronic invisible college”. The results of a survey of scientists attending the Laxenburg conference in 1997 illustrates the transdisciplinary and international nature of HDGC research, the local and international scale of research, their commitment to public policy, and their increased use of the Internet for networking, data acquisition and analysis, and publication. 相似文献
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Glenn R. Flierl 《Dynamics of Atmospheres and Oceans》1977,1(5):443-453
We have solved several linear quasigeostrophic problems in singly and multiply connected domains to illustrate the use and effects of correct boundary conditions which balance circulation changes with forcing along each boundary. The results with these boundary conditions differ markedly from those obtained by setting the streamfunction to zero on the walls either when the fluid is forced by a time-dependent wind stress curl or when the fluid oscillates in a free basin mode in a domain which contains interior islands. 相似文献
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H. Larrain F. Velsquez P. Cereceda R. Espejo R. Pinto P. Osses R. S. Schemenauer 《Atmospheric Research》2002,64(1-4)
Fog collection data registered through a Standard Fog Collector (SFC) installed by a local fishermen's association at a height of 600 m at the “Falda Verde” site, north of the Chilean harbor Chañaral (26°17′S/70°36′W), from November 1998 to November 2000, are analyzed. Trying to give new lights on the dynamics of fog along the Chilean northern coast, this article compares, for the first time, the data obtained at Falda Verde with those obtained at five other Chilean fog stations. The total time period runs from 1987 to 2001. A mean of 1.46 l/m2/day was registered at the Falda Verde site after 2 years of measurements, one of the lowest yields along the north Chilean coast. After a brief historical recapitulation of fog researches in the study area, geographical explanations of the water yields obtained in different sites are discussed. The annual mean collection from Cerro Moreno and Paposo shows a clearly different behavior from all other sites, showing a greater stability throughout the year. Other stations have a marked difference between extreme seasons. Alto Patache yields, if not the best in Chile, are very high and offer unexpected possibilities for future applications in the coast. Stations located away from the seashore (Cerro Guatalaya) are clearly less productive. Ocean proximity, altitude, south and southwest orientations of the coastal ranges and local relief explain some of the differences noted. 相似文献