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1.
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   

2.
Summary Mechanisms associated with Alpine lee cyclogenesis during the early phase of their generation are investigated using a variational quasigeostrophic filter technique. It was possible to extract the quasigeostrophic signal from the available analyzed real data set.The results presented here are for the 11–12 March 1982, an example of so-called orographically induced lee cyclogenesis. Non-quasigeostrophic fields, calculated as a difference between observations and the quasigeostrophic fields, show significant magnitudes indicating the possible importance of non-quasigeostrophic processes. A dipole structure in the residual geopotential field was observed, similar to the results of numerical model experiments. Also, a strong upper-level non-quasigeostrophic divergence was found in the Alpine region 24 hours prior to lee cyclogenesis, lasting for 6–12 hours. On the other hand, quasigeostrophic results indicate only a local effect of mountain slopes, suggesting possibly a dominant role of the low-level blocking. A hypothetical scenario of Alpine lee cyclogenesis is proposed, based on results obtained here.With 14 Figures  相似文献   

3.
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   

4.
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   

5.
The variations of and in the drainage flow in the Brush Creek valley of western Colorado are investigated using data from Doppler acoustic sodars and instrumented towers. The data were obtained on two experimental nights during the 1984 ASCOT field study. There is good agreement between the variations derived from low-level observations of the sodars and those derived from the towers located throughout the valley. The observed hourly average and in the nocturnal drainage flow are about 20 ° to 25 ° and 5 °, respectively; these values are much larger than those generally observed over flat terrain during nighttime stable conditions. After sunrise (about 0600 MST), as the valley warms and the flow direction changes to up-valley, these parameters increase sharply to their peak values at about 0800 MST and then decrease to their normal daytime values after about two hours.In the drainage flow, the hourly average varies inversely with wind speed according to the relation u 0.7ms-1. The vertical standard deviation is much less enhanced by complex terrain than the horizontal standard deviation. The observed values are predicted fairly well by the local similarity theory.Oak Ridge Associated Universities (ORAU) Summer Research Participant at ATDD in 1987 andOak Ridge Associated Universities (ORAU) Summer Research Participant at ATDD in 1987 and  相似文献   

6.
A liquid jet of 90 m diameter and variable length has been utilized to determine absorption rates and, hence, mass accommodation coefficients , of atmospheric trace gases. The compounds investigated are HCl (0.01), HNO3 (0.01), N2O5 (0.005), peroxyacetyl nitrate (>0.001), and HONO (0.005). It is concluded that the absorption of these trace gases by liquid atmospheric water is not significantly retarded by interfacial mass transport. The strengths and limitations of the liquid jet technique for measuring mass accommodation coefficients are explored.  相似文献   

7.
The study focuses on a way to parameterize the effect of subgrid scale convective motions on surface fluxes in large scale and regional models for the case of light surface winds. As previously proposed, these subgrid effects are assumed to scale with the convection intensity through the relationship: where is the mean velocity of the wind, U0 the velocity of the mean wind, w* the free convection velocity, and an empirical coefficient to be determined. Both observations and numerical simulation are presently used to determine the free convection coefficient .Large eddy simulation of a fair weather convective boundary layer case observed during TOGA-COARE is performed. Comparisons between observations and the simulation of surface properties and vertical profiles in the planetary boundary layer are presented. The simulated vertical turbulent fluxes of heat, moisture and buoyancy range well within estimates from aircraft measurements.The most important result is that the true free convection coefficient , directly estimated from simulation, leads to a value of 0.65, smaller than the ones estimated from temporal and spatial variances. Using observations and simulation, estimates of from temporal and spatial variances are obtained with similar values 0.8. From both theoretical derivations and numerical computations, it is shown that estimates of the true from variances are possible but only after applying a correction factor equal to 0.8. If this correction is not used, is overestimated by about 25%. The time and space sampling problem is also addressed in using numerical simulations.  相似文献   

8.
Summary In the first part of the present paper all cases of orographically induced cyclogeneses in the Western Mediterranean (40 cases) during the whole 13 months of the ALPEX Observing Period (AOP: 1 September 1981–30 September 1982) are investigated statistically to find similarities between them. It can be shown that essentially there exist two different types of such cyclogeneses: the Vorderseiten-type (southwesterly upper-level flow) and the Überströmungs-type (northwesterly upper-level flow). Both types are accompanied by low level blocking of cold air by the Alps. The second part of the paper is concerned with the understanding of the explosive development of an orographically induced cyclone in the Western Mediterranean by means of vorticity dynamics on isentropic surfaces. Budget equations for the shear and curvature vorticity allow us to find out the reasons for the increase of curvature vorticity, locally as well as individually. Such growth rates are caused by corresponding convergences and by transformation from shear into curvature vorticity, respectively. Case studies of some ALPEX-SOP cyclogeneses illustrate the vorticity-dynamical considerations.
Zur Synoptik und Dynamik orographisch induzierter Zyklogenesen im Mittelmeerraum
Zusammenfassung In der vorliegenden Studie werden zunächst alle orographisch induzierten Zyklogenesen im westlichen Mittelmeerraum (40 Fälle) während der gesamten 13 monatigen ALPEX-Beobachtungsperiode (AOP: 1. September 1981–30. September 1982) einer statistischen Untersuchung unterzogen, um Gemeinsamkeiten herauszufinden. Dabei zeigte es sich, daß im wesentlichen zwei Typen von derartigen Zyklogenesen auftreten: der Vorderseiten-Typus und der Überströmungs-Typus. In beiden Fällen kommt es dabei in den unteren Luftschichten zur Blockierung der Kaltluft durch die Alpen. Im weiteren wird dann die vielfach explosionsartige Entwicklung der orographisch induzierten Zyklogenese im westlichen Mittelmeer mit Hilfe der Vorticitydynamik auf isentropen Flächen zu verstehen versucht. Die Aufspaltung der Bilanzgleichung für die Vorticity in eine Bilanzgleichung für die Scherungs- und in eine Bilanzgleichung für die Krümmungsvorticity, erlaubt das genaue Wachstumsstudium der Krümmungsvorticity sowohl lokal als auch individuell. Derartige Wachstumsraten kommen durch entsprechende Konvergenzen bzw. durch die Umwandlung von Scherungs- in Krümmungsvorticity zustande Mehrere Fallstudien von ALPEX-SOP veranschaulichen diese wirbeldynamischen Überlegungen.

With 9 Figures  相似文献   

9.
Summary The forntal passage of 8 October 1987, which was extensively sampled during the first intense observation period of the German Front Experiment, is simulated by aid of three mesoscale models. The results are intercompared and held against the manually and objectively analysed observations of the meso and meso- scales, respectively. The orographic impact is studied by comparing model runs with full and cut-off Alps. Implications regarding similar efforts in the future conclude the paper.With 11 Figures  相似文献   

10.
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   

11.
Stable Isotope Ratios: Hurricane Olivia   总被引：1，自引：0，他引：1  
The oxygen and hydrogen isotopic compositions of rains from HurricaneOlivia (1994) in the eastern Pacific were measured. The rains werecollected on 24 and 25 September during airplane flights conducted at anelevation of 3 km. Hurricane Olivia peaked in intensity to a category-4storm between the two dates. Isotope ratios of rains from HurricaneOlivia were markedly lower ( 18O = –13.9to –28.8) than that of rain collected from a thunderstormat an elevation of 2.3 km outside the influence of Olivia (18O = –3.8). A distinct decrease in isotoperatios from the first day to the next ( 18O =–18.4 to –21.9) in Hurricane Olivia wasattributed to decreased updraft velocities and outflow aloft. Thisshifted the isotopic water mass balance so that fewer hydrometeors werelifted and more ice descended to flight level. A decrease in the averagedeuterium excess from the first day to the next (d = 15.5 to 7.1)was attributed to an increase in the relative humidity of the watervapor `source' area. We hypothesize that the `source' region for therain was in the boundary layer near the storm center and that becausethe hurricane was at peak intensity prior to the second day the relative humidity was higher.  相似文献   

12.
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   

13.
Airborne measurements made during August 1985 over Greenland and its environs show that both accumulation-mode (0.1 m D2.0 m) and giant (D2 m) particles were present in relatively high concentrations in arctic haze layers and that the accumulation-mode particles dominated light scattering. Particles with diameters (D) between 1 and 4 m consisted predominately of mixed materials, small and dense inclusions, and probably organic compounds containing sulfur. Many of the particles from 0.1 to 1 m in diameter were also of mixed composition, with sulfuric acid, ammonium sulfate and organics probably the dominant constituents.  相似文献   

14.
Thermal comfort of man in different urban environments   总被引：2，自引：4，他引：2  
Summary On July 29, 1985, a hot summer day, biometeorological measurements were performed simultaneously in three different urban structures within the city of Munich and in the trunk space of a nearby tall spruce forest. Based on the results of these experiments the following thermophysiologically relevant biometeorological indices were calculated: Predicted mean vote, skin wettedness and physiologically equivalent temperature. These three indices are derived from different models for the human energy balance. They allow the assessment of the thermal components of the microclimates at the selected sites with regard to application in urban planning. The results quantitatively show the great heat stress in the urban structure street canyon, exposed to south, whereas in the trunk space of the tall spruce forest there is nearly an optimal climate even on hot summer days. Between these extremes the results for street canyon, exposed to north show a little higher heat load than for backyard with trees.
Zusammenfassung An einem heißen Sommertag, dem 29. Juli 1985, wurden in drei Stadtstrukturen in München und im Stammraum eines nahegelegenen Fichtenhochwaldes zeitgleich biometeorologische Messungen durchgeführt. Mit den Meßergebnissen wurden folgende thermophysiologisch relevante biometeorologische Indizes berechnet: Predicted mean vote, Hautbenetzungsgrad und physiologisch äquivalente Temperatur. Diese drei Indizes beruhen auf verschiedenen Modellen zur menschlichen Energiebilanz. Mit den drei Indizes wurden die thermischen Komponenten der Mikroklimate an den ausgewählten Meßplätzen im Hinblick auf Stadtplanungsaufgaben bewertet. Die Ergebnisse zeigen quantitativ die relativ große Hitzebelastung bei der Stadtstruktur Straßenschlucht, nach Süd exponiert, während im Stammraum des Fichtenhochwaldes selbst an heißen Sommertagen nahezu optimale Bedingungen herrschen. Zwischen diesen Extremen liegen die Ergebnisse für die anderen Meßplätze, wobei für Straßenschlucht, nach Nord exponiert die Wärmebelastung etwas höher als für Innenhof mit Bäumen ist.

With 6 Figures  相似文献   

15.
Summary The investigations during the German Frontal Experiment 1987 show the modification of structure and movement of cold fronts in the vicinity of the Alps and in an Alpine valley. The two cold fronts that moved nearly parallel to the mountains were modified at the mountain barrier by the channelling effect. In those cases the postfrontal air flowed into the Inn valley from the valley's exit up-valley. The upper and lower parts of the fronts became detached, and the structure of the lower part changes on its way from the foreland to the mountain barrier.In contrast the fourth cold front, which moved from north-west to south-east, crossed the mountains without appreciable deformation although it suffered some degree of blocking and retardation.With 7 Figures  相似文献   

16.
Surface-Layer Fluxes in Stable Conditions   总被引：2，自引：2，他引：0  
Micrometeorological tower data from the Microfronts experiment are analyzed. Scale-dependencies of the flux and flux sampling error are combined to automatically determine Reynolds turbulence cut-off time scales for computing fluxes from time series. The computed downward heat flux at the 3 m height averaged over nine nights with 7.3 hours each night is 20% greater than the downward heat flux computed at the 10 m height. In contrast, there is only a 1.2% difference between 3 m and 10 m heat fluxes averaged over daytime periods, and there is less than a 2% difference between 3 m and 10 m momentum fluxes whether averaged over nighttime or daytime periods.Stability functions, M(z/L) and H(z/L) are extended to z/L up to 10, where z is the observational height and L is the Obukhov length. For 0.01 < z/L < 1 the estimated functions generally agree with Businger-Dyer formulations, though the H estimates include more scatter compared to the M estimates. For 1 < z/L < 10, the flux intermittency increases, the flux Richardson number exceeds 0.2, and the number of flux samples decreases. Nonetheless the estimates of the stability function M based on 3-m fluxes are closer to the formula proposed by Beljaars and Holtslag in 1991 while the M functions based on 10-m fluxes appears to be closer to the formula proposed by Businger et al. in 1971. The stability function H levels off at z/L = 0.5.  相似文献   

17.
Résumé Après avoir rappelé quelques notions de calcul tensoriel et les équations de la dynamique atmosphérique en coordonnées généralisées, l'auteur établit l'équation fondamentale de la rotationnelle absolue de l'air. Diverses formes de cette équation sont mentionnées. La première de ces formes est celle d'un bilan qui permet de définir le transport et le taux de production de la rotationnelle absolue de l'air. De la forme particulière de ce transport, il résulte que ce bilan se réduit à un bilan dans un espace à deux dimensions. Deux exemples illustrent les formules générales, le premier, en coordonnées sphériques (, ,r), le second, en coordonnées (, , ) où est un scalaire quelconque (pression atmosphérique, température potentielle, ...). Une autre forme de l'équation fondamentale est celle qui donne le taux d'accroissement individuel d'une composante de la rotationnelle absolue. Cette forme conduit à l'équation d'Ertel. En terminant, l'auteur généralise l'invariant d'Ertel-Rossby.
Summary Having recalled some results of the tensor analysis and the equations of atmospheric motion in general coordinates, the writer establishes the fundamental equation of the absolute vorticity. Different forms of this equation are mentioned. One of these is the equation of balance from which it is possible to deduce the definition of transport and production of vorticity. It is shown that the equation of balance of the absolute vorticity may be reduced to an equation of balance in two-dimensional space. Two examples illustrate the general equations and formulas: the first example, in spherical coordinates (, ,r), the second one in the coordinates (, , ) where is an arbitrary single-valued scalar quantity (pressure, potentiel temperature, ...). Another form of the absolute vorticity equation expresses the individual change of an arbitrary component of the absolute vorticity. This form leads toErtel's equation. Finally, the writer generalizes theErtel-Rossby invariant.
Zusammenfassung Nach einer Rekapitulation einiger Resultate der Tensorrechnung und der atmosphärischen Bewegungsgleichungen in generalisierten Koordinaten wird die absolute Wirbelgleichung aufgestellt und es werden verschiedene Formen dieser Gleichung erwähnt. Eine derselben ist die Bilanzformel, aus der die Definition des Wirbeltransports und der Anteil der Wirbelbildung abgeleitet werden können. Es wird gezeigt, daß die Bilanzgleichung des absoluten Wirbels auf eine Bilanzgleichung im zweidimensionalen Raum reduziert werden kann. Die allgemeinen Formeln werden durch zwei Beispiele erläutert: das erste in Kugelkoordinaten (, ,r), das zweite in den Koordinaten (, , ), wo eine beliebige skalare Größe (luftdruck, potentielle Temperatur usw.) darstellt. Eine andere Form der absoluten Wirbelgleichung gibt die individuelle Zunahme einer beliebigen Komponente der absoluten Wirbelstärke wieder; diese Form führt zurErtelschen Gleichung. Zum Schlusse wird dieErtel-Rossbysche Invariante verallgemeinert.
  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.
A previously published technique for using tethered spherical balloons as anemometers for measuring light low-level winds has been further developed. Earlier data on the relationship between the aerodynamic drag coefficient and the Reynolds number of spherical rubber balloons were combined with a large number of new data and re-analysed; and the errors in the relationship were estimated. The results allowed a more accurate calculation of wind speed from the deflection of a tethered balloon from the vertical. When combined with a new technique for calculating the effects of the tether, this enabled light to moderate low-level winds at fixed heights up to 600 m or more to be measured with simple, cheap, and readily mobile equipment; and a slight modification of the technique allowed measurement of winds in and above fog. Wind speeds measured by the ballon technique showed reasonably good agreement with measurements by an anemometer carried beneath the balloon.Glossary of Symbols a, b, c Coefficients in the relationship between lnC d and lnR - A Quantity under square root in solution for lnV whena0 - C d Wind drag coefficient for balloon - C dc Value ofC d given by calibration curve of Table I - D Dynamic wind pressure force on balloon - F Buoyant free lift of balloon with load - Re Reynold's number of balloon (sphere) - R = Re/105 - r Radius of sphere - T Tension in tether - V Wind speed - 83() =(lnC dc -lnC d ) when 83° , or 0 for other - Error in lnC d - Elevation of tether where attached to balloon - Elevation of balloon from ground tether point - Molecular viscosity of air - Ratio of circumference to diameter of circle - Density of air  相似文献   

20.
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   

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