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1.
Six locations across mainland Portugal were selected for exposing Parmelia sulcata, for a one-year period (8 months for one site), with simultaneous measurement of total (dry + wet) deposition (one-month periods). The exposed lichens and the total (dry + wet) deposition were analysed for cobalt contents by INAA (instrumental neutron activation analysis) and ICP-MS (inductively coupled plasma mass spectroscopy), respectively. The designated wet deposition was evaluated through the collected water volume; the designated dry deposition was assessed after the (dried) residual mass of the wet deposition. An excellent agreement between Co contents in exposed lichens and the cumulative (1) Co contents in the dry deposition, (2) dry deposition, and (3) wet deposition has been found for the locations with alternate drought and precipitation months, high dry deposition, and high Co contents in the latter. Continuous rainfall was found to hinder the Co accumulation in the lichen due to its release from the lichen and/or lower Co contents in the dry deposition. At three locations, P. sulcata Co contents, after subtraction of the background (before exposure), equalled or exceeded the Co contents in the cumulative dry deposition at the end of the exposure time. The optimal exposure period for this species likely depends on the exposure conditions.  相似文献   

2.
Summary The performance of evaporation schemes with and approach and their combination within resistance representation of evaporation from bare soil surface is discussed. For this purpose nine schemes, based on different functions of or , on the ratio of the volumetric soil moisture content and its saturated value are used.The quality of the chosen schemes has been evaluated using the results of time integration by the coupled soil moisture and surface temperature prediction model, BARESOIL, using in situ data. A sensitivity analysis was made using two sets of data derived from the volumetric soil moisture content of the top soil layer. One with values below the wilting point (0.17 m3m–3) and the second with values above 0.20m3m–3. Data sets were obtained at the experimental site Rimski anevi, Yugoslavia, from the bare surface of a chernozem soil.With 4 Figures  相似文献   

3.
The aerodynamic classification of the resistance laws above solid surfaces is based on the use of a so-called Reynolds roughness number Re s =h s u */, whereh s is the effective roughness height, -viscosity,u *-friction velocity. The recent experimental studies reported by Toba and Ebuchi (1991), demonstrated that the observed variability of the sea roughness cannot be explained only on the basis of the classification of aerodynamic conditions of the sea surface proposed by Kitaigorodskii and Volkov (1965) and Kitaigorodskii (1968) even though the latter approach gains some support from recent experimental studies (see for example Geernaertet al. 1986). In this paper, an attempt is made to explain some of the recently observed features of the variability of surface roughness (Toba and Ebuchi, 1991; Donelanet al., 1993). The fluctuating regime of the sea surface roughness is also described. It is shown that the contribution from the dissipation subrange to the variability of the sea surface can be very important and by itself can explain Charnock's (1955) regime.  相似文献   

4.
Summary An analysis of the report of the (U.S.) National Academy of Sciences (NAS) on atmospheric effects of a nuclear exchange leads to conclusions that differ from those of the NAS and of the earlier TTAPS and AMBIO studies. Any cooling of the earth's surface is likely to beshort-lived because of rapid removal of the smoke clouds originating from nuclear burst-initiated fires, andminor because of appreciable green-house effects due to several distinct physical causes. (One of these, neglected in prior analyses, is the infrared absorption from cirrus clouds produced directly by the nuclear bursts.) Taken together, these effects may even induce slight surface warming (nuclear summer) instead of cooling (nuclear winter). The consequences to atmospheric ozone are similarly ambiguous; depending on the detailed nuclear scenario, the net ozone content may increase-rather than decrease as argued by TTAPS. Experiments could settle some uncertainties.With 2 Figures  相似文献   

5.
Whether in classical networks such as meteorological networks of in more recent ones of atmospheric chemistry, a wealth of data is at hand. These data have been evaluated in a manner depending on the purpose of the network. However, much more information is hidden in these time series and waits for discovery. Only the imagination of scientists is needed. Four examples are given which lead to new information about the atmospheric aerosol and the behaviour of the atmosphere. These examples are: Atmospheric turbidity from sunshine recordings, Meteorological drainage area from the variance of observations, Location of point sources from air mass trajectories, and Total vertical ozone from turbidity measurements.  相似文献   

6.
Parameterizing turbulent diffusion through the joint probability density   总被引：3，自引：3，他引：0  
The convective mass flux parameterization often used in meteorological modeling expresses the vertical flux of a transported scalar as proportional to the product of the difference in mean values of the scalar in updrafts and downdrafts and their characteristic velocity. The proportionality factor is a constant to be specified. We show that this proportionality factor also appears in the relaxed eddy accumulation technique of Businger and Oncley. That associates the surface-layer flux of a scalar with the product of the standard deviation of vertical velocity and the mean concentration difference between updrafts and downdrafts.We show that this constant (b) is determined uniquely by the joint probability density (jpd) of vertical velocity and the scalar. Using large-eddy simulation, we generate this jpd for a conservative scalar diffusing through a convective boundary layer. It has quite different forms in top-down and bottom-up diffusion geometries. The bottom-up jpd is fairly well represented by a jointly Gaussian form and implies b ~ 0.6, in good agreement with the surface-layer value reported by Businger and Oncley. The top-down jpd is strikingly non-Gaussian and gives b ~ 0.47. Updrafts carry the bulk of the scalar flux - 70% in the bottom-up case, 60% in the top-down case.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

7.
Summary The interannual variations in sea surface temperature (SST) in the equatorial east Pacific, which are dominated by the El Niño phenomenon, are shown for the period 1870–1983. Since 1870 25 significant warm events have occurred. These events are classified as weak, moderate, strong and very strong, according to the normalized SST anomalies in the region 130° W–80° W, 0°–5° S.The spatial and temporal development of a composite El Niño/Southern Oscillation (ENSO) episode, based on 10 very strong or strong events, is presented in terms of SST, surface wind and divergence anomalies for the tropical Pacific (10° N–30° S). During its evolution the following phases are distinguished: Antecedent Conditions, Onset Phase, Peak Phase, Mature Phase and Dissipation Stage.Some aspects of ocean-atmosphere interaction associated with this evolution and, more specifically, the initiation of the composite event, are described. Seasonally varying feedback processes between SST, surface wind and convergence anomaly patterns in the western Pacific/Indonesian region suggest a possible mechanism for the initiation of typical ENSO events.
Zusammenfassung Die interannuären Variationen der Meeresoberflächentemperatur (SST) im äquatorialen Ostpazifik, die von dem El Niño-Phänomen dominiert werden, werden für die Periode 1870–1983 aufgezeigt. Seit 1870 traten 25 signifikante Ereignisse auf. Diese Ereignisse werden entsprechend den normierten SST-Anomalien in der Region 130° W–80° W, 0°–5° S als schwach, mittel, stark und sehr stark klassifiziert.Die räumliche und zeitliche Entwicklung einer Komposit-El Niño/Southern Oscillation (ENSO)-Episode, die auf 10 sehr starken bzw. starken Ereignissen basiert, wird anhand von SST-, Bodenwind- und Divergenzanomalien für den tropischen Pazifik (10° N–30° S) dargestellt. Während ihrer Entwicklung werden die folgenden Phasen unterschieden: Vorausgehende Bedingungen, Einsetzphase, Spitzenphase, Reifestadium und Auflösungsstadium.Einige Aspekte der Wechselbeziehungen Ozean—Atmosphäre werden im Zusammenhang mit der Entwicklung und insbesondere der Auslösung des Komposit-Ereignisses beschrieben. Jahreszeitlich variierende Rückkopplungsprozesse zwischen SST-, Bodenwind- und Konvergenzanomalien in der westpazifischen/indonesischen Region stellen einen möglichen Mechanismus für die Auslösung typischer ENSO-Ereignisse dar.

With 9 Figures  相似文献   

8.
Zusammenfassung An einem Material von 100 Fällen eindeutig gesicherten Herztodes, die im Institut für Gerichtliche und Soziale Medizin in Frankfurt am Main aus einem bestimmten Bereich — Raum Frankfurt am Main — und einer bestimmten zeit—Kalenderjahre 1948 bis 1950—zur Autopsie gelangten, einerseits und den bioklimatischen Daten für den gleichen Raum und die gleiche Zeit anderseits, wurde der Zusammenhang von Herztodesfällen und Wettervorgängen mit der Wahrscheinlichkeitsüberlegung, dem Wahrscheinlichkeitsintegral und formalstatistischen Methoden überprüft. Die Auswertung ergab, daß eine starke Abhängigkeit des Herztodes vom Wettergeschehen besteht. Die Häufung der Herztodesfälle konnte für die Sammelgruppe Wetterstörungen, für labiles Aufgleiten, Warmfront mit Aufgleiten und Kaltfront mit Turbulenz ebenso eindeutig gesichert werden, wie die Verminderung der Herztodesfälle in störungsfreien Zeiten. Die hohe Wahrscheinlichkeit einer Beziehung besteht ferner für Kaltfront mit Aufgleiten und in geringerem Maße auch für Föhndurchbruch. Während bei Okklusion das Material zu einem abschließenden Urteil zu gering war, konnte bei allen übrigen Wetterlagen eine Beziehung zum plötzlichen Herztod nicht nachgewiesen werden. Auch für die Gruppen, bei denen eine enge Beziehung statistisch gesichert werden konnte, sei betont, daß die Wettervorgänge nicht die alleinige Ursache des plötzlichen Herztodes, sondern nur ein auslösendes Moment bei schon vorher schwer geschädigten Herzen darstellen.
Summary On the basis of 100 ascertained cases of cardiac death from a certain region—province Frankfort on-the-Main—and a certain period—calendar years 1948 to 1950—, submitted to autopsy in the Institute for Legal and Social Medicine at Frankfort on-the-Main, and of bioclimatic data from the same region and period, the relation between cardiac death and meteorological phenomena was examined by means of probability considerations, the probability integral, and methods of formal statistics. Evaluation of this material showed cardiac death to be strongly dependent on weather conditions. Increase of frequency of cardiac death could be established without any doubt for the collective groups weather disturbances, unstable ascending motion, warm front with ascending motion, cold front with turbulence, whereas decrease of frequency was found in undisturbed periods. Furthermore, high probability of an existing relation was found for cold front with ascending motion and, to a lesser degree, also for foehn invasion. As to occlusion no definite conclusions could be drawn for scarcity of observations. For all the other weather types no relation to sudden cardiac death could be proved. Meteorological phenomena are by no means the only cause of sudden cardiac death, not even for the groups in which a close relation could be established statistically. They have but an initiatory effect in case of prior severe heart diseases.
Résumé Disposant d'un matériel médical de 100 cas de mort cardiaque qui ont fait l'objet d'autopsies à l'Institut de médecine légale et sociale de Francfort sur le Mein (région de Francfort et période de 1948 à 1950), et disposant d'autre part pour la même région et pour la même période d'observations bioclimatologiques, l'auteur a étudié la relation de ces décès avec les phénomènes météorologiques à l'aide des méthodes modernes de statistique, de l'intégrale de probabilité etc. Le résultat montre une étroite dépendance centre les cas de mort cardiaque et les conditions météorologiques. On a pu vérifier sans doute possible l'augmentation des décès lors de «perturbations», d'«ascendances labiles», de «fronts chauds avec glissement ascendant», de «fronts froids avec turbulence», de même que leur diminution lors de périodes non troublées. La forte corrélation subsiste avec les «fronts froids avec ascendance» et à un moindre degré avec «l'invasion du foehn». Tandis que pour les «occlusions» le matériel disponible était trop restreint pour aboutir à une conclusion, l'examen des situations autres que les précédentes n'a pas conduit à une relation intime. Il convient de remarquer que pour tous les groupes de météores ayant donné une corrélation statistique très nette, les phénomènes météorologiques n'ont joué qu'un rôle déclancheur chez des malades déjà gravement atteints.

Mit 2 Textabbildungen.  相似文献   

9.
Periodicity of annual precipitation in different climate regions of Croatia   总被引：1，自引：1，他引：0  
Summary The periodicity of a 100-year series of annual precipitation over Croatia has been studied by means of power spectrum analysis at 3 stations representing the different climatic regions of Croatia. The annual precipitation variance spectra in the continental lowland (Osijek) and at the north East Adriatic coast (Crikvenica) can be fitted by Markov white noise continuum, but in the transitional region between the Dinaric Alps and the Pannonian lowland (Zagreb-Gri) a non-white noise continuum is necessary. Quasi-periodic oscillations appear in two spectra ranges: short (2.2 and 4.7 years) and medium (25.0 and 33.3 years). These results are compared with those of other authors for other parts of the Europe.With 2 Figures  相似文献   

10.
Zusammenfassung Es werden numerische Integrationen der dreidimensionalen Fickschen Diffusionsgleichung mit höhenabhängigen Diffusionskoeffizienten und Windgeschwindigkeit für den stationären Fall und eine kontinuierlich emittierende Punktquelle durchgeführt. Für die drei typischen Ausbreitungsverhältnisse Starke Durchmischung, Bodeninversion und Inversion über der Quelle, charakterisiert durch die Diffusionskoeffizienten und die Windgeschwindigkeit, werden die Einflüsse unterschiedlicher Quellhöhe, Sinkgeschwindigkeit und Ablagerungsgeschwindigkeit studiert.
Summary Numerical integrations of the threedimensional Fickean diffusion equation with height dependent diffusion coefficients and wind velocity are performed in the stationary case with a continuous point source. For the three typical cases strong mixing, surface inversion and inversion above the source characterized by the diffusion coefficients and wind velocity, the effects of source height, sinking velocity and deposition velocity are discussed.
Résumé Les auteurs ont procédé à l'intégration numérique de l'équation à trois dimensions de la diffusion, équation établie par Fick. Ils ont, pour cela, utilisé des coefficients de diffusion variant avec l'altitude et la vitesse du vent et distingué l'état stationnaire et le cas d'une source d'émission ponctuelle et continue. Ils étudient en outre les influences de hauteurs différentes de la source, de la rapidité de subsidence et de la vitesse de sédimentation. Ils ont tenu compte pour cela des trois conditions typiques de diffusion mélange très accentué, inversion au sol et inversion au-dessus de la source.

Mit 7 Textabbildungen  相似文献   

11.
ALPEX-Simulation     
Summary In a project ALPEX-Simulation, sponsored by the Österreichischer Fond zur Förderung der wissenschaftlichen Forschung (FWF), all eight cases of ALPEX-SOP cyclones were numerically simulated with a fine mesh isentropic model of the atmosphere. These numerical simulations in six-hourly intervals allow a deeper insight into the synoptics and dynamics of the cyclogeneses in the Western Mediterranean, especially into the genesis of the two basic types of cyclones: the so-called Überströmungs-type and Vorderseiten-type. In the first phase of cyclogenesis of the Überströmungs-type, the blocking and flow splitting of the cold air due to the Alps and the canalization between the Alps and the Massif Central are important. Cold air flows cyclonically around the western part of the Alps, creating a vorticity maximum at the south western edge of the Alpine, bow and leads also to an enhanced PV. In connection with warm air in the Mediterranean, a strong baroclinic zone is generated. The interaction between the arriving PV maximum in the upper troposphere and the enhanced PV at the bottom leads to cyclogenesis in the Western Mediterranean. In the case of the Vorderseiten-type warm air advection dominates with the exception of a shallow layer of cold air in the inner Po-Valley, which is shielded by the Alpine ridge. A well-pronounced PV maximum builds up and couples with the PV maximum arriving at upper levels, even before the cold air, coming from the north-west, has surrounded the Alps. The cold air only intensifies the development by raising the baroclinity. Therefore, the Vorderseiten-cyclogenesis is an orographically modified cyclogenesis, in the course of which the cyclonic development is triggered by the Alps, whereas the Überströmungs-cyclogenesis is an orographically induced cyclogenesis i.e. a true lee cyclogenesis.With 14 FiguresDied in a tragic traffic accident on June 6, 1993.  相似文献   

12.
Analyses indicate that the Atlantic Ocean seasurface temperature (SST) was considerably colder at the beginning than in the middle of the century. In parallel, a systematic change in the North Atlantic sea-level pressure (SLP) pattern was observed. To find out whether the SST and SLP changes analyzed are consistent, which would indicate that the SST change was real and not an instrumental artifact, a response experiment with a low-resolution (T21) atmospheric GCM was performed. Two perpetual January simulations were conducted, which differ solely in the Atlantic Ocean (40° S-60° N) SST: the cold simulation utilizes the SSTs for the period 1904–1913; the warm simulation uses the SSTs for the period 1951–1960. Also, a control run with the model's standard SST somewhat between the cold and warm SST was made. For the response analysis, a rigorous statistical approach was taken. First, the null hypothesis of identical horizontal distributions was subjected to a multivariate significance test. Second, the level of recurrence was estimated. The multivariate statistical approaches are based on hierarchies of test models. We examined three different hierarchies: a scale-dependent hierarchy based on spherical harmonics (S), and two physically motivated ones, one based on the barotropic normal modes of the mean 300 hPa flow (B) and one based on the eigenmodes of the advection diffusion operator at 1000 hPa (A). The intercomparison of the cold and warm experiments indicates a signal in the geostrophic stream function that in the S-hierarchy is significantly nonzero and highly recurrent. In the A-hierarchy, the low level temperature field is identified as being significantly and recurrently affected by the altered SST distribution. The SLP signal is reasonably similar to the SLP change observed. Unexpectedly, the upper level stream-function signal does not appear to be significantly nonzero in the B-hierarchy. If, however, the pairs of experiments warm versus control and cold versus control are examined in the B-hierarchy, a highly significant and recurrent signal emerges. We conclude that the cold versus warm response is not a small disturbance that would allow the signal to be described by eigenmodes of the linear system. An analysis of the three-dimensional structure of the signal leads to the hypothesis that two different mechanisms are acting to modify the model's mean state. At low levels, local heating and advection are dominant, but at upper levels the extratropical signal is a remote responce to modifications of the tropical convection.This paper was presented at the International Conference on Modelling of Global Climate Change and Variability, held in Hamburg 11–15 September 1989 under the auspices of the Meteorological Institute of the University of Hamburg and the Max Planck Institute for Meteorology. Guest Editor for these papers is Dr. L. Dilmenil.AWI Publication no. 254  相似文献   

13.
Summary Koshava is a gusty wind of moderate to strong intensity, blowing from the south-eastern direction, over the area of the Republic of Serbia. It is caused by the interaction between the synoptic circulation and the orography of the Carpathian and the Balkan mountains. The Koshava wind can damage buildings, factories and industrial plants or city infrastructure. Therefore it is important to estimate its gust and the gustiness factor on the basis of the measured data.This paper discusses a statistical analysis of wind data in the maximum influence area of the Koshava wind in the periods of maximum duration of Koshava. The focus of the paper is the examination of urban and suburban effects on Koshava wind and the correlation between the instantaneous maximum wind speed and the hourly mean wind speed. The best fitting with various empirical distributions is proposed.With 10 Figures  相似文献   

14.
Summary With the typical geometry of a large Alpine valley in mind, a box-type model consisting of only one (Alpine) basin, the forelands, and one valley tube connecting those two has been set up. Using drastically simplified equations of motion, continuity and heat, and supposing weak-gradient synoptic conditions, a periodic solution for the daily wave of the valley wind regime is obtained.Fundamental concepts like the area-height distribution of valley segments, or the role of slope winds and other fast-reacting local circulations in heating or cooling the main valley and larger basins, are being incorporated. The solution has valley wind speeds correct in amplitude and phase, maximum upvalley wind occurring around 16 h local time. Valley winds attempt to equalize horizontal pressure differences, which are caused by the fact that the interior of valleys is being heated and cooled more strongly by a factor of 2 or more than the atmosphere over the adjacent plain = foreland. In this attempt, they reduce the temperature contrast somewhat, but not very much, because friction in the valley is a dominating process. The present model also nicely reproduces observed features of the daily pressure wave, including the existence of a level of pressure equalization (between the valley interior and the plain) at about crest height.
Grundzüge eines Talwindmodells
Zusammenfassung Ich habe das typische Relief eines großen Alpentals vor Augen, und konstruiere ein Schachtel-Modell, das drei schematische Regionen umfaßt: ein inneralpines Becken, das Alpenvorland, und eine Talröhre, die diese beiden verbindet. Die Impuls-, Kontinuitäts- und thermodynamische Gleichung werden in stark vereinfachter Form angesetzt, wobei eine gradientschwache Wetterlage vorausgesetzt wird. Wir untersuchen die tagesperiodische Lösung dieses Systems für Talwind, Temperatur, Luftdruck. In diesen Gleichungsansatz wurden grundlegende Konzepte eingearbeitet: z.B. die Flächen-Höhenverteilung des Beckens, oder die Rolle der Hangwinde und anderer kleinräumiger, schnell reagierender thermischer Zirkulationen, die die lokale Erwärmung/Abkühlung dem Haupttal bzw. größeren Talbecken mitteilen. Die vorliegende Lösung zeigt Talwindgeschwindigkeiten, deren Amplitude und Phase mit den Beobachtungen gut übereinstimmen: der Taleinwind hat sein Maximum um ca. 16 Uhr Lokalzeit (MEZ). Die Talwinde sind ein Versuch, horizontale Druckdifferenzen auszugleichen, die wiederum auf Grund der Tatsache entstehen, daß die Erwärmung/Abkühlung des Taiinneren um mehr als den Faktor 2 stärker ist als die der Luftsäule über dem angrenzenden Vorland. Bei diesem Versuch reduzieren die Talwinde den Temperaturkontrast, aber nur um weniges, da die Ausgleichsströmung durch die Talröhre starker Reibung unterliegt. Schließlich reproduziert das vorliegende Modell in zufriedenstellender Weise den tagesperiodischen Druckgang, wie er in verschiedenen Höhen beobachtet wird, vor allem auch das sogenannte Druckausgleichsniveau, das ungefähr in Kammhöhe liegt.

With 2 Figures  相似文献   

15.
This article presents nine statements which are generally accepted as true. However, when they are applied to a particular situation, in this case the recent prolonged drought in the Sahelian zone in West Africa, they are as often untrue as they are true. For example, such generalizations as people learn from their mistakes or when the rains come, everything will return to normal or technology is the answer, when applied uncritically to a specific situation often prove to become part of the problem as well as a hindrance to the attainment of a solution to that problem.It is strongly suggested that these nine generalizations, here called fallacies, be carefully assessed when applied, thereby removing one more obstacle in dealing with environmental problems in general and natural hazards in particular.Published in Michael H. Glantz (ed.), The Politics of Natural Disasters: The Case of the Sahel Drought (NY: Praeger Publ., 1976) reprinted by permission.Michael H. Glantz is a scientist in the Advanced Study Program at the National Center for Atmospheric Research which is sponsored by the National Science Foundation.  相似文献   

16.
Summary ¶In order to better understand land-atmosphere interactions and increase the predictability of climate models, it is important to investigate the role of forest representation in climate modeling. Corresponding to the big-leaf model commonly employed in land surface schemes to represent the effects of a forest, a so called big-tree model, which uses multi-layer vegetation to represent the vertical canopy heterogeneity, was introduced and incorporated into the National Center for Atmospheric Research (NCAR) regional climate model RegCM2, to make the vegetation model more physically based. Using this augmented RegCM2 and station data for China during 1991 Meiyu season, we performed 10 experiments to investigate the effects of the application of the big-tree model on the summer monsoon climate.With the big-tree model incorporated into the regional climate model, some climate characteristics, e.g. the 3-month-mean surface temperature, circulation, and precipitation, are significantly and systematically changed over the model domain, and the change of the characteristics differs depending on the area. Due to the better representation of the shading effect in the big-tree model, the temperature of the lower layer atmosphere above the plant canopy is increased, which further influences the 850hPa temperature. In addition, there are significant decreases in the mean latent heat fluxes (within 20–30W/m2) in the three areas of the model domain.The application of the big-tree model influences not only the simulated climate of the forested area, but also that of the whole model domain, and its impact is greater on the lower atmosphere than on the upper atmosphere. The simulated rainfall and surface temperature deviate from the originally simulated result and are (or seem to be) closer to the observations, which implies that an appropriate representation of the big-tree model may improve the simulation of the summer monsoon climate.We also find that the simulated climate is sensitive to some big-tree parameter values and schemes, such as the shape, height, zero-plane displacement height and mixing-length scheme. The simulated local/grid differences may be very large although the simulated areal-average differences may be much lower. The area-average differences in the monthly-mean surface temperature and heat fluxes can amount to 0.5°C and 4W/m2, respectively, which correspond to maximum local/grid differences of 3.0°C and 40W/m2 respectively. It seems that the simulated climate is most sensitive to the parameter of the zero-plane displacement among the parameters studied.  相似文献   

17.
Vegetable Crops for Biomonitoring Lead and Cadmium Deposition   总被引：5，自引：0，他引：5  
Leafy vegetables are of particular interest for the active biomonitoring of the heavy metal deposition in the environment. The leaves accumulate the deposited airborne trace elements, however, they are also influenced by soilborne metals. The level of root uptake and accumulation depends on the element concerned and specific plant characteristics that influence the sensitivity of the biomonitoring system to a large extend. Standardization of the soil substrate and a precise estimation of the root uptake are very important in order to improve the sensitivity of biomonitoring. Spinach (Spinacea oleracea), lettuce (Lactuca sativa), endive (Cichorium endivia) and lambs lettuce (Valerianella locusta), grown in containers filled with a common peat soil and supplied with a semi-automatic watering system, were successfully used as bioaccumulators for the Cd and Pb deposition in gardens of an industrial and a residential area. Comparisons were made between the Cd and Pb contents in the crops and the deposition flux measured with NILU particulate fallout collectors in order to determine the accumulation efficiency of each crop. The correlations found were very useful to estimate the tolerable dust deposition levels with reference to the EU Guideline for maximum levels of contaminants in leafy vegetables. Exposure of the crops in open-top chambers, which were supplied with filtered air, (provided with a roof), proved that the Pb dust deposition significantly increases the normal concentration in the vegetables from the reference area, whereas the cadmium deposition was too low to be measured biologically. Comparisons of exposure of the crops to ambient air with or without chamber enclosure, and in open-top chambers with filtered air allowed to determine the normal metal concentrations and to estimate the biological detection limits.  相似文献   

18.
Parameterization of evaporation from a non-plant-covered surface is very important in the hierarchy strategy of modelling land surface processes. One of the representations frequently used in its computation is the resistance formulation. The performance of the evaporation schemes using the , , and their combination resistance approaches to parameterize evaporation from bare soil surfaces is discussed. For that purpose, the nine schemes, based on a different dependence of and on volumetric soil moisture content and its saturated value, are used.The tests of performances of the considered schemes are based on time integrations by the land surface module (BARESOIL) using observed data. The 23 data sets at a bare surface experimental site in Rimski anevi, Yugoslavia on chernozem soil, were used for the resistance algorithm evaluation. The quality of the schemes was compared with the observed values of the latent heat flux using several statistical parameters.  相似文献   

19.
Summary A simple method of representing cumulative frequency distributions ofk-day period amounts of precipitation (30k1800), deduced from observations at Hoofddorp during 87 years and from observations at Winterswijk during 73 years, by means of cumulative Poisson distributions, had been developed. Poisson's constant appeared to depend linearly onk only, while the Poisson unitq appeared to be only proportional to the annual variation.In this paper it is shown that the representation of observed cumulative frequency distributions with the aid of Poisson distributions is true for any station in The Netherlands in the interval 30k1800. A map with isopleths of -values fork=360 presents a simple picture, so that for any station an -value fork=360 can be estimated. For the process of representation the meank-day period amount of precipitation is also necessary. This value may be obtained from a map for each of the 12 months, each map covered with isohyetal lines, which give a distribution of the monthly precipitation.
Zusammenfassung Es wurde eine Methode entwickelt, um in einfacher Weise Summenfunktionen vonk-tägigen Niederschlagsmengen (30k1800), welche aus Beobachtungen in Hoofddorp während 87 Jahren und in Winterswijk während 73 Jahren angestellt worden sind, durch kumulative Poissonsche Häufigkeitsverteilungen darzustellen. Dabei ergab sich, daß die Poissonsche Konstante nur linear vonk abhängig ist, während die Poissonsche Einheitq sich als proportional zum Jahresgang erwies.In der vorliegenden Untersuchung wird nun gezeigt, daß die Darstellung der beobachteten kumulativen Häufigkeitsverteilungen mit Hilfe von Poisson-Verteilungen für irgendeine Station in den Niederlanden im Bereich von 30k1800 gültig ist. Eine Karte mit Isoplethen der -Werte fürk=360 ergibt ein einfaches Bild, aus dem für jede beliebige Station ein -Wert fürk=360 abgelesen werden kann. Für eine solche Darstellung muß auch die Niederschlagsmenge derk-tägigen Perioden bekannt sein; diese Werte erhält man aus monatlichen Isohyeten-Karten, die die monatliche Niederschlagsverteilung wiedergeben.
Résumé On avait développé une méthode pour représenter d'une façon simple les distributions des sommes cumulées dek jours (30k1800) des quantités de précipitations déduites des observations faites à Hoofddorp pendant 87 ans et à Winterswijk pendant 73 ans. On avait démontré que la constante de Poisson ne dépend dek que linéairement et que l'unité de Poissonq est proportionnelle à la variation annuelle.De la présente étude ressort que, dans l'intervalle de 30k1800, la représentation des distributions des fréquences cumulées observées au moyen des formules de Poisson est valable pour une station quelconque aux Pays-Bas. Une carte d'isoplèthes de la valeur pourk=360 donne une image suffisamment simple pour que la valeur d'une station quelconque aux Pays-Bas puisse être déterminée sans difficulté. Pour une telle représentation il faut connaître également les moyennes des quantités des périodes dek jours de la précipitation. Ces valeurs peuvent se déduire de cartes mensuelles des isohyètes moyennes.

With 1 Figure

Dedicated to Dr.Anders K. Ångström on the occasion of his 70th birthday.  相似文献   

20.
Summary Hybrid modeling entails the combination of a numerical weather prediction model and a symbolic model. The latter uses symbolic objects, their characterizing attributes and sets of behavioral constrains which prescribe changes in the states of these objects as functions of time, space, and other imposed quantitative or heuristic conditions. Integration of these two modeling components for an on-line, real-time, operational system is feasible only if both the numerical and the symbolic model can be executed in a distributed mode, i.e. at a user's location rather than in a central weather service office. This condition entails the design of a numerical model that can run on relatively inexpensive desktop workstations or high-end PCs. Given such a capability, the output from the numerical model can be used to satisfy a number of behavioral constraints of objects (such as thunderstorm, blizzard, etc.), defined in the symbolic model. These constraints can be embedded invisibly as functions of time and pixel location on the computer screen, to be called upon as soon as the respective object is activated, e.g. by placing an icon on the screen.To make such a hybrid weather prediction model responsive to details in topography, it will have to be able to interface with a geographic information system (GIS) database. Since such databases can be very voluminous, management procedures for indexing and rapid information retrieval have to be instituted. The approach discussed here involves restructuring of given GIS data into B+ trees.The hybrid prediction model whose design is described in this paper, executes very quickly on a PC (e.g. a 33 megahertz Intel 80486 chip based machine). It allows assimilation of locally generated observational data to improve forecast quality, and can respond to queries of a highly specialized nature in support of tactical decisions within the time frame between nowcasting (3 hours) and 24 hours.With 6 Figures  相似文献   

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