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1.
Field data are analyzed in order to study the layer-averaged winds in the unstable, entraining, baroclinic, advective and non-stationary Planetary Boundary Layer (PBL). The relationship between the actual and geostrophic winds is described using three different equation sets. The results of these analytical expressions are compared with measurements from the Öresund experiment which was carried out during the period May 15 to June 14, 1984.  相似文献   

2.
A three-dimensional, non-hydrostatic mesoscale model is used to study boundary-layer structure over an area characterized by the city of Copenhagen, the Øresund strait, and adjacent coastal farmland. Simulations are compared with data obtained on June 5, 1984 during the Øresund experiment.Under moderately strong wind conditions, a stable internal boundary layer (IBL) developed over the Øresund strait during the day. Near-surface winds decelerate over water due to diminished vertical momentum transfer.The turbulent kinetic energy field closely reflects the surface roughness distribution due to the imposed relatively strong wind forcing. TKE budgets over water, farmland and a city area are discussed by inspection of vertical profiles of the individual terms. The buoyancy term is used to indicate IBL heights because it changes sign at the boundary between different stability regimes. Measured and simulated dissipation rates show a decrease in the transition zone as the air travels over water and an abrupt increase when the IBL over a downwind city area is intersected. The top of the stable IBL is characterized by a minimum in the vertical TKE profile.  相似文献   

3.
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4.
A numerical two-dimensional-mesoscale model with a level 1.5 closure scheme for turbulence is described. The model is used to simulate the boundary layer over coastal complex terrain. Meteorological data available from the Øresund land-sea-land terrain experiment are used to study the performance of the model. The model could simulate generally observed complexities in the mean wind and temperature fields. Internal boundary layers over the water and land surfaces were identified by the height of lowest value in the turbulence kinetic energy profile and this showed good agreement with radiosonde (RS) observations.Some disagreements with the data were also noticed, especially near the surface. The wind speed was over-predicted. Attempts were made to improve the model performance by adopting different schemes for model initialisation. Results showed that initialisation with an early model start time and observed wind profile near the inflow boundary improved the performance. The wind speed over-prediction could be further minimised by using a more realistic objective initialisation scheme. The problem centred around the proper estimation of the turbulent diffusion coefficient K through the closure scheme. Despite using the most popular empirical relationships in the level 1.5 closure scheme, these differences persisted. While this needs further investigation, the present model can be used to supply wind fields for practical purposes such as air pollution calculations.  相似文献   

5.
Data from the Öresund experiment are used to investigate the structure of the stably stratified internal boundary layer (SIBL) which develops when warm air is advected from a heated land surface over a cooler sea. The present study is based on a theory developed by Stull (1983a, b, c). He proposed that the turbulence and the mean structure of the nocturnal boundary layer is controlled by the time-integrated value of surface heat flux and that the instantaneous heat flux is of less importance.Dimensional arguments are used to define simple, physically consistent, temperature, velocity and length scales. The dimensionless surface heat flux has a high value immediately downwind of the shoreline and it decreases rapidly in magnitude with increasing distance from the coast. Farther away, it is essentially constant. The dimensionless potential temperature change exhibits an exponential profile. It is estimated that turbulence accounts for 71% of boundary-layer cooling while clear-air radiational cooling is responsible for the remaining 29%.Finally it is found that theoretical predictions for the height of the SIBL are in a good agreement with observations.  相似文献   

6.
Summary Results are presented of three years' measurements at Aspendale of net, global and diffuse radiation (R, G andD respectively) as well as of short-wave radiation on a north-facing surface (G N ).The results are compared with other Australian radiation measurements, and the local character of the constants inÅngström type estimation formulae pointed out. A term is given which corrects such formulae by taking into account the uneven distribution of cloudiness over the day. The effect of orographic cloud on radiation is also discussed.After correction for climatological mean conditions, Aspendale summer values ofG are about 18% higher than those ofBlack [4] and ofBudyko [7]; the winter values agree reasonably. Summer and winter values ofR are considerably higher thanBudyko's—about 21% and 28% respectively. In addition some disagreement is found with the Australian Radiation Records 1953–1956.In winter, the amounts of diffuse and solar radiation (G-D) are about equal.
Zusammenfassung Die Resultate dreijähriger Registrierungen der Strahlungsbilanz, der Global- und der Himmelsstrahlung (R, G undD) sowie der kurzwelligen Strahlung auf eine Nordwand (G N ) werden mitgeteilt.Die Ergebnisse werden mit anderen australischen Strahlungsmessungen verglichen, und die örtliche Abhängigkeit der Konstanten in den vonÅngström angegebenen Formeln wird hervorgehoben. Es wird eine Korrekturgröße in die Formeln eingeführt, mit der der Einfluß der ungleichmäßigen Verteilung der Bewölkung über den Tag erfaßt werden kann. Ferner wird der Effekt der orographisch bedingten Bewölkung auf die Strahlungssummen diskutiert.Es ergibt sich, daß nach Anbringung einer Korrektur auf klimatologische Durchschnittsverhältnisse die Globalstrahlungswerte von Aspendale im Sommer ungefähr um 18% größer sind als die vonBlack [4] und vonBudyko [7] angegebenen Werte; die Winterwerte stimmen einigermaßen überein. Sommer- und Winterwerte vonR sind um ungefähr 21% und 28% größer alsBudykos Werte. Es wurden auch Unterschiede zwischenG und den Australian Radiation Records 1953–1956 festgestellt.Im Winter sind die Beträge der Himmels- und der Sonnenstrahlung (G-D) annähernd gleich.
Résumé On décrit les résultats obtenus durant trois ans d'enregistrements du bilan du rayonnement, de la radiation globale et de celle du ciel (R, G etD), ainsi que du rayonnement d'ondes courtes reçu par une paroi exposée au nord (G N ).Ces résultats sont alors comparés à d'autres mesures australiennes du rayonnement et l'on en tire la dépendance locale des constantes contenues dans les formules d'Ångström. On introduit ainsi un facteur de correction dans les dites formules. Ce facteur permet de tenir compte de l'influence des fluctuations de la nébulosité au cours de la journée. En outre, on discute les répercussions qu'ont les nuages orographiques sur les sommes de rayonnement.Il en résulte que, après l'application de la correction, les valeurs tirées des conditions climatologiques moyennes sont pour l'été, selon Aspendale, environ 18% supérieures à celles indiquées parBlack [4] et parBudyko [7], bien que les quantités hivernales correspondent à peu près. Les valeurs estivales et hivernales deR sont, elles, environ 21% et 28% plus importantes que celles deBudyko. On constate également une différence entreG et les «Australian Radiation Records» 1953–1956.Les valeurs de la radiation du ciel et du soleil (G-D) sont à peu près équivalentes en hiver.

With 13 Figures  相似文献   

7.
Aircraft-based vertical flux measurements fill a gap in the spatial domain for studies of biosphere–atmosphere exchange. To acquire valid flux data, a determination of the deviation from the mean vertical wind, w′, is essential. When using aircraft platforms, flux measurements are subject to systematic and random errors from airflow distortion caused by the lift-induced upwash ahead of the aircraft. Although upwash is typically considered to be a constant quantity over periods used for calculating fluxes, it can vary significantly over short (and longer) periods due to changes in aircraft lift. The characterization of such variations in upwash are of undeniable importance to flux measurements, especially when real-time computations of w′ are required. In this paper, the variability in upwash was compared to the calculated upwash from the model of Crawford et al. (Boundary-Layer Meteorol, 80:79–94, 1996) using data taken during a long-period (phugoid mode) free oscillation of the aircraft. The cyclic variation of lift during the free oscillation offers an ideal scenario in which to acquire in-flight data on the upwash that is present, as well as to test the capability of upwash correction models. Our results indicate that while this model corrects for much of the mean upwash, there can be significant variations in upwash on a time scale that is important to flux measurements. Our results suggest that use of the measured load factor could be an easily implemented operational constraint to minimize uncertainty in w′ due to changing upwash from changing aircraft lift. We estimate, using the phugoid data, and from variations in aircraft attitude and airspeed in flux-measurement configuration, that the uncertainty in w caused by variable upwash is approximately ± 0.05 m s−1.  相似文献   

8.
Summary Eleven months of atmospheric turbidity measurements were made in Tozeur, Southern Tunisia, located at the northern edge of the Sahara. These measurements were done with a Linke-Feussner actinometer equipped with broad band Schott filters (OG1, RG2, RG8). These filters were chosen, as they have demonstrated a good stability with time. The lowest values of turbidity were found in winter, which is the rainy season for this area. In spring (April) the largest number of sand storms were observed, but the turbidity remained high for the whole summer. A mean Linke turbidity factor of 5.39 was derived, which is a value otherwise generally found only in industrial areas. Mean values of Ångström coefficients were = 0.34 and = 1.20.Aerosol particles were also sampled with nucleopore membrane filters. The chemical analyses of the particles with an X-ray spectrometer showed that most of the smaller ones had a chemical composition similar to sand. Other, larger ones showed high amounts of Ca and Cl; these are believed to have originated in Chott Djerid, the largest dried-out salt lake in Tunisia, which is located 20 km southeast of Tozeur.Model calculations of the radiative transfer for the solar spectrum were carried out, taking the turbidity measurements and ground truth measurements of albedo [33] into account. A perturbation experiment was carried out, changing turbidity and surface reflectivity. It was found that an increased surface reflectivity had a cooling effect at the surface, and a warming effect on the lowest kilometer of the atmosphere. Further, increases in turbidity resulted again in cooling at the surface, but with additional warming of the atmosphere. The combined increases of surface reflectivity and turbidity had a somewhat balancing effect as far as planetary albedo was concerned.
Messungen der Trübung des Aerosols der Sahara und ihre Auswirkungen auf die Erwärmung der Atmosphäre und auf die planetare Reflexionsfähigkeit
Zusammenfassung Elf Monate hindurch wurden in Tozeur in Süd-Tunesien am Nordrand der Sahara Messungen der atmosphärischen Trübung durchgeführt. Diese Messungen wurden mit einem Linke-Feussner gemacht, das mit Breitband Schott-Filter OG1, RG2 und RG8 ausgerüstet ist. Die kleinsten Trübungswerte wurden im Winter gefunden, der für dieses Gebiet die Regenzeit ist. Im Frühling (April) wurde die größte Zahl von Sandstürmen beobachtet und die Trübung blieb auch im ganzen Sommer groß. Es wurde ein mittlerer Trübungsfaktor nach Linke von 5.39 bestimmt. Das ist ein Wert, der im allgemeinen nur in Industriegebieten gefunden wird. Die Mittelwerte der Ångström-Koeffizienten betrugen = 0,34 und = 1,20.Mit Membranfiltern wurden auch Aerosolteilchen gesammelt. Die mit einem Röntgenstrahlen-Spektrometer durchgeführten chemischen Analysen der Teilchen zeigten, daß die kleineren Teilchen meist eine dem Sand ähnliche chemische Zusammensetzung haben. Größere Teilchen zeigten hohe Beträge von Ca und Cl. Diese haben ihren Ursprung scheinbar im Chott Djerid, dem größten ausgetrockneten Salzsee in Tunis, der 20 km südöstlich von Tozeur liegt.Es wurden Modellrechnungen der Strahlungsübertragung für das Sonnenspektrum durchgeführt, wobei die Trübungsmessungen und die Albedomessungen in Rechnung gezogen worden sind. Es wurden auch Störungsexperimente mit geänderter Trübung und Oberflächenreflexion durchgeführt. Es wurde gefunden, daß zunehmende Oberflächenreflexion einen Abkühlungseffekt an der Oberfläche und einen Erwärmungseffekt im untersten Kilometer der Atmosphäre zeigt. Ferner bewirkt eine Zunahme der Trübung ebenfalls eine Abkühlung der Oberfläche, aber zusätzliche Erwärmung der Atmosphäre. Die kombinierte Zunahme der Oberflächenreflexion und der Trübung hatte einen etwas ausgleichenden Effekt, soweit die planetare Albedo betroffen war.

With 13 Figures  相似文献   

9.
Measurements of stratospheric NO2 by ground-based visible spectrometers rely on laboratory measurements of absorption cross-sections. We review low-temperature laboratory measurements, which disagree by amounts claimed to be significant. Our recalculation of their errors shows that in general disagreements are not significant and that errors in the ratios of cross-sections at low to room temperature are between ±3% and ±8.8%. Of these errors, up to ±3.5% was contributed by errors in the equilibrium constant,K p, in those measurements where the pressure was above 0.1 mbar.We review measurements and calculations ofK p, which were accurate to ±5% from 300 to 233 K. Each method was potentially flawed. For example, infrared measurements of the partial pressure of NO2 ignored the dependence of absorption on total pressure. From thermodynamic theory, formulae forK pcan be derived from expressions for the variation of heat capacity with temperature. Contrary to common belief, coefficients in the formulae used by spectroscopists were not derived from the thermodynamic quantities. Rather, they were fitted to measurements or to calculations. Hence, they are empirical and it is dangerous to extrapolate below 233 K, the lowest temperature of the measurements.There are no measurements of NO2 cross-sections below 230 K. Extrapolation of these cross-sections to analysis of measurements of NO2 at the low temperatures of the Arctic and Antarctic stratosphere is also dangerous. For satisfactory analysis of polar spectra, the NO2 cross-sections should be measured at temperatures down to 190 K with a relative accuracy of ±1%. This difficult experiment would need a cell of minimum length 32 m whose length can be adjusted. Because their effects are circular, many errors cannot be removed simply. Although circular errors also arise in the measurements ofK pand of the infrared spectrum, their weights differ from those in the visible spectrum. The optimum experiment might therefore simultaneously measure the visible and infrared spectra andK p.  相似文献   

10.
The comparison between the precipitable water vapor w obtained by classical sounding and that obtained by high resolution measurements of spectral solar direct irradiance in the 400–1000 nm spectral range is shown. Three different water vapor absorption functions in the πστ band are used to determine the water vapor w by optical measurements. An episode of attenuation of direct solar irradiance by cirrus clouds is also shown.  相似文献   

11.
The temporal and spatial variations in the surface albedo of the Vatnajökull ice cap, Iceland, are investigated. A time series of the surface albedo is composed for the summer of 1996 using satellite radiance measurements from the Advanced Very High Resolution Radiometer (AVHRR). This time series is compared with ground measurements carried out during a glacio-meteorological experiment during the same summer on the ice cap. The AVHRR is able to reproduce the development in time of the surface albedo fairly well. The large systematic differences found for some of the stations on the ice are attributed to sub-pixel-scale variations in the albedo. An attempt is made to confirm this hypothesis using satellite radiance measurements carried out by the Thematic Mapper (TM) and measurements made with a portable albedometer. The TM has a pixel size of 30 × 30 m whereas the pixel size of the AVHRR is 1 × 1 km. Although the TM measurements show greater variability in the albedo than do the AVHRR measurements, the large systematic difference remains. Measurements with the portable albedometer show a large spread in the albedo at sites with large systematic differences. This implies that the scale of the albedo variations is smaller than the scale of the AVHRR and TM pixels.  相似文献   

12.
Zusammenfassung An einer Innbrücke wurden mittels Rauchfäden Messungen des von der Flußoberfläche erzeugten Windprofiles angestellt. Es konnte gezeigt werden, daß die Profile dem logarithmischen Ansatz vonPrandtl genügen. Bei annähernder Windstille in höheren Luftschichten verhielt sich die Wasseroberfläche an der Meßstelle wie einerauhe Grenzfläche mit dem konstanten Rauhigkeitsparameterz 0=1.09 cm. Der Einfluß des strömenden Wassers machte sich dabei bis in ca. 3 m Höhe bemerkbar. Bei stärkeren Talaufwinden (größeren Relativgeschwindigkeiten zwischen Luft und Wasser) nimmt der Rauhigkeitsparameter sprunghaft sehr kleine Werte an (4.3. 10–6 cm), und es scheinen sich Strömungs-verhältnisse wie überglatten Grenzflächen einzustellen.
Summary From a bridge on the Inn River measurements of wind profiles produced by the streaming water have been made with the aid of smoke traces. It could be shown that these profiles followPrandtl's logarithmic law. With approximately zero wind speed in the upper levels of the profiles the water surface behaved like a rough boundary surface having a constant roughness parameter ofz 0=1.09 cm. The influence of the running water could be traced up to a height of about 3 m. With a stronger valley breeze (higher relative velocities between air and water surface) the roughness parameter is decreasing abruptly to very small values (4.3. 10–6 cm), and conditions as over asmooth surface seem to be established.
Résumé L'auteur a mesuré le profil de vent produit par la rivière depuis un pont sur l'Inn à l'aide de fumées. Ces profils satisfont à la loi logarithmique dePrandtl. Par temps calme en altitude, la surface de l'eau se comporte comme une surface rugueuse avec un paramètre de rugosité constant et égal à 1.09 cm; l'influence de l'eau courante se fait sentir jusqu'à trois mètres de hauteur environ. Par brise d'aval assez forte, le paramètre devient subitement beaucoup plus petit (4.3. 10–6 cm), et il semble s'établir des conditions d'écoulement de l'air correspondant à des surfaces de glissement lisses.

Mit 8 Textabbildungen.  相似文献   

13.
A comprehensive set of trace gas concentrations and meteorological parameters were measured simultaneously during a cruise of the research vessel Polarstern from Bremerhaven (54° N, 8° E) to Rio Grande (32° S, 52° W) during the period from 15 September to 9 October 1988. This paper describes the general features of the cruise and summarizes the measurements made, the techniques employed, and the placement of the instruments on board the ship. The synoptic data base is used to characterize the nature and possible origins of the air masses encountered during the cruise and to draw some general conclusions from the measurements.  相似文献   

14.
The diffusion of particulate matter from an elevated source   总被引：2，自引：0，他引：2  
Summary The problem of the diffusion of particulate matter from an elevated source is important to industry, to agriculture and to public health. On the experimental and theoretical side, simple ground measurements of this phenomenon offer very sensitive tests of diffusion theories.A theoretical solution to this problem, using theK-theory formulation byDeacon [1], but valid only for neutral stability, was given byRounds [2] in 1955 and has been extended by approximate methods to cover any stability by the present author. Calculations then show the dependence of down-wind distribution of deposited matter on stability, surface roughness, height of source, wind speed and particle size. The effects on the location and magnitude of maximum deposition produced by simultaneous variations in two or more of the above parameters are also portrayed.The formulation bySutton [3] of the statistical theory (theC-theory) has been applied to particulate diffusion by numerous authors, who give differing solutions largely as a result of inconsistent boundary assumptions. A formally correct solution is derived, but a fundamental reexamination of the turbulence mechanism described by theC-theory reveals that this theory is probably not applicable to diffusion from an elevated source near the ground (although it may give essentially the correct ground concentration for gaseous aerosols). In addition, theK-theory has a decided advantage for practical application in that all the parameters required are inherent in the vertical profile of wind speed.
Zusammenfassung Das Problem der Diffusion suspendierter Partikel von einer Quelle in der Höhe besitzt Bedeutung für Industrie, Landwirtschaft und öffentliche Hygiene. Von experimenteller und theoretischer Seite biete schon einfache Bodenmessungen dieses Vorganges sehr empfindliche Prüfmöglichkeiten für Diffusionstheorien.Eine theoretische Lösung dieses Problems, die auf derK-Theorie-Formulierung vonDeacon [1] beruht, jedoch nur für neutrale Stabilität Gültigkeit besitzt, wurde vonRounds [2] 1955 angegeben und wurde vom Verfasser der vorliegenden Arbeit durch Näherungsmethoden auf beliebige Stabilitätsbedingungen ausgedehnt. Berechnungen haben ergeben, daß die Abhängigkeit der Verteilung der Abwärtsströmungen der abgelagerten Materie von der Stabilität, der Bodenrauheit, der Höhe des Ausgangspunktes, der Windgeschwindigkeit und der Partikelgröße abhängig ist. Die Wirkungen, die durch gleichzeitige Variation von zwei oder mehr der genannten Parameter auf die Lokalisierung und das Ausmaß der maximalen Ablagerung hervorgerufen werden, konnten ebenfalls dargestellt werden. Suttons [3] Formulierung der statistischen Theorie (C-Theorie) wurde von zahlreichen Forschern auf die Partikeldiffusion angewendet, die im wesentlichen infolge unvereinbarer Grenzvoraussetzungen zu verschiedenartigen Lösungen gekommen sind. Es wird eine formell korrekte Lösung aufgestellt; doch ergibt eine auf die Grundtatsachen zurückgehende Überprüfung des Turbulenzmechanismus, wie er von derC-Theorie formuliert wird, daß diese Theorie wahrscheinlich nicht auf den Vorgang der Diffusion von einem erhöhten Ausgangspunkt in der Nähe des Bodens anwendbar ist (wenn sie auch in den Grundzügen in der Lage ist, die korrekte Bodenkonzentration für gasförmiges Aerosol wiederzugeben). Zudem hat dieK-Theorie einen entschiedenen Vorzug für die praktische Anwendung durch den Umstand, daß alle erforderlichen Parameter im Vertikalprofil der Windgeschwindigkeit enthalten sind.
Résumé Le problème de la diffusion de particules en suspension issues d'une source en altitude revêt une certaine importance pour l'industrie, l'agriculture et l'hygiène publique. Du point de vue expérimental et théorique, même des mesures au sol de ce phénomène offrent de fines possibilités de vérification des théories de la diffusion.La solution de ce problème fondée sur la théorie deDeacon [1], mais qui ne vaut que pour une stabilité neutre, a été donnée parRounds [2] en 1955 et a été étendue par l'auteur à d'autres conditions quelconques de stabilité par des méthodes d'approximation. Le calcul montre que les courants descendants de particules dépendent de la stabilité, de la rugosité du sol, de l'altitude de la source, de la vitesse du vent et de la grosseur des particules. L'auteur a pu aussi apprécier l'effet des paramètres variables mentionnés sur la localisation et le dépôt maximum.De nombreux chercheurs ont appliqué la théorie deSutton à la diffusion des particules et ont abouti à diverses solutions, en raison probablement de conditions aux limites incompatibles. L'auteur établit une formule correcte; mais l'examen du mécanisme de turbulence tel qu'il est formulé dans la théorie deSutton [3] montre que cette dernière n'est probablement pas applicable au voisinage du sol dans le cas d'une diffusion ayant sa source en un point élevé, bien qu'elle puisse fournir la concentration correcte dans le cas d'un aérosol gazéiforme. En outre la théorie deDeacon présente un net avantage pour les applications, du fait que tous les paramètres nécessaires sont contenus dans le profil vertical de la vitesse du vent.

Published by permission of the Director, Meteorological Branch, Department of Transport, Canada, and dedicated to Dr.Anders K. Ångström on the occasion of his 70th birthday.  相似文献   

15.
Zusammenfassung Auf dem Hohen Sonnblick (3106 m) wurden im Sommer 1950 Wärmeumsatzuntersuchungen durchgeführt. Über die hierbei ausgeführten Messungen der Sonnenstrahlung, Himmelsstrahlung, Gegenstrahlung der Atmosphäre, der Albedo und der langwelligen Temperaturausstrahlung des Gletschers wird hier berichtet. Es konnte die Einwirkung der Bewölkung auf die Himmelsstrahlung studiert werden. Bestimmungen der Gegenstrahlung über Bilanzmessungen ergaben die Brauchbarkeit derÅngströmschen Formel und bestimmte Gesetzmäßigkeiten des Einflusses der Wolkendecke. Als anscheinend variabelster Faktor wird die zeitlich und örtlich oft sehr wechselnde Albedo angesehen. Einige Beispiele direkter Strahlungsbilanzmessungen, die dies beweisen, werden mitgeteilt.
Summary A report is given of measurements of solar radiation, sky radiation, atmospheric radiation, albedo, and long-wave outgoing radiation of a glacier carried out in connection with investigations on exchange of heat on the High Sonnblick (3106 m) in summer 1950. The effects of cloudiness on sky radiation were studied. Determinations of atmospheric radiation derived from balance measurements showed the validity of theÅngström-formula and certain regularities concerning the effect of cloud cover. The most variable factor appears to be the albedo which often varies strongly with time as well as locally. Several examples of direct measurements of radiation balance proving that are communicated.
Résumé On a effectué au sommet du Sonnblick (3106 m) en été 1950 des recherches sur les échanges de chaleur. On rapporte ici sur les mesures faites du rayonnement solaire et céleste, du rayonnement atmosphérique de l'albédo et du rayonnement à grande longueur d'onde du glacier. On a pu établir l'influence de la nébulosité sur le rayonnement céleste. Des évaluations du rayonnement atmosphérique tirées de mesures du bilan thermique ont prouvé la validité de la formule d'Ångström ainsi que certaines règles concernant l'effet de la couverture du ciel. Le facteur apparemment le plus variable est l'albédo qui varie parfois fortement dans le temps et dans l'espace. Quelques exemples de mesures directes du bilan radiatif qui le prouvent sont donnés.

Mit 6 Textabbildungen.  相似文献   

16.
Summary A sun photometer fitted with 9 narrowband interference filters from 368 nm to 1024 nm was used to determine the aerosol optical depth at 8 measuring stations in Europe. Of the 9 filters, 4 were not included in the standard equipment of the sun photometer. Given the temporal instabilities of the calibration factors of these 4 filters, meaningful results for the aerosol optical depth can be achieved only if calibration and measurements follow each other closely. Calibration was performed using the Langley plot method. For wavelengths < 500 nm, the measured aerosol optical depths were compared with the results of a high resolution spectrometer. Broadband aerosol optical depths, centred at 427 nm, were determined with an actinometer and were also used for comparison. Generally, there was good agreement of the results. To characterize the aerosol optical depths, the Ångström parameters and were used. The individual measuring stations showed a clustered distribution of and values.With 6 Figures  相似文献   

17.
Zusammenfassung Aus der Gesamtheit aller Aerosolteilchen in der natürlichen Luft, deren Radius sich über den Größenbereich von 10–7 bis 5×10–4 cm erstreckt, erfaßt das Zeißsche Konimeter den Ausschnitt oberhalb etwar=1×10–5 cm. Die großen Kerne dieses Teilchenbereiches, die bisher irrtümlicherweise als Staub bezeichnet wurden, sind dabei völlig wesensgleich mit den anderen Kernen. Es wird mit dem Segelflugzeug die vertikale Verteilung dieser großen Kerne gemessen und gezeigt, daß die Konimetermessungen zwar nur Relativwerte liefern, aber trotzdem brauchbare Resultate ergeben. Ein Vergleich mit gleichzeitigen Messungen des vertikalen elektrischen Spannungsgefälles zeigt einen bemerkenswerten Zusammenhang, der qualitativ deutbar ist. Eine große Zahl von Einzelmessungen ergibt ein Bild von der Verteilung der großen Kerne bis zu einer Höhe von 3000 m NN.
Summary From the whole of all aerosol particles in the natural air, the radius of which embraces the amplitude of 10–7 to 5×10–4 cm, we can measure the sector of aboutr=10–5 cm and more with the Zeiss conimeter. The great nuclei of this range which hitherto, by misunderstanding, were qualified as dust are of the same nature as the other nuclei. The vertical distribution of these great nuclei has been measured with a glider, and it is shown that measurements with the conimeter yield only relative values, but the results are, however, comparable. A comparison with simultaneous measurements of the vertical electric potential gradient shows a remarkable correlation which can be interpreted qualitatively. A great number of single measurements leads to a picture of the distribution of the great nuclei up to a height of 3000 m a. s. l.
Résumé Avec le conimètre Zeiss il est possible d'observer les particules de l'aérosol de l'air naturel d'un rayon plus grand que 10–5 cm, tandis que la totalité des particules embrasse des rayons allant de 10–7 à 5×10–4 cm. Les grands noyaux qui, autrefois, étaient faussement désignés comme poussière, sont absolument de même nature que les autres. Au moyen d'un planeur on a mesuré la répartition verticale de ces gros noyaux et, de cette façon, on a pu montrer que les mesures du conimètre, bien que ne fournissant que des valeurs relatives, donnent tout de même des résultats utiles. Une comparaison avec des mesures simultanées du gradient de potentiel électrique vertical, fait apparaître une corrélation remarquable qui peut être interprêtée qualitativement. Un grand nombre de mesures donne une image de la répartition des gros noyaux jusqu'à 3000 m d'altitude.

Mit 8 Textabbildungen

Die Untersuchung ist in den Jahren 1943–44 bei der Deutschen Forschungsanstalt für Segelflug Ainring (Oberbayern) entstanden. Infolge verschiedener Umstände ist die Veröffentlichung erst heute möglich und es konnten deshalb einige neuere Ergebnisse miteingearbeitet werden. Für entsprechende Hinweise und Hilfe bin ich den HerrenChr. Junge undM. Diem zu Danke verpflichtet. Der Verfasser.  相似文献   

18.
Summary Whole-plant transpiration (T) measurements have many applications, but appropriate methods have remained somewhat elusive. A new method using a constant power heat balance gauge, wherein the xylem mass flow rate is calculated from a balance of heat into and out of a stem, has been shown to provide accurate stem flow measurements. To evaluate the applicability of this promising method to field experiments, cotton (Gossypium hirsutum L. GP 3774) stem flow measurements were compared withT measured from a weighing lysimeter. Initially to confirm method accuracy, stem flow values were compared in the glasshouse withT values determined by mass measurements of a potted plant. The root mean square error (RMSE) between the daylight losses from both (n = 16) was 8.6% of the mean measuredT values. In the field, hourly stem flow and lysimeterT values were also similar, but there was a large variation in stem flow values among the different plants. To account for differences in plant size between the plants with gauges and all lysimeter plants, stem flow values were adjusted using a stem area ratio factor, which adjusted values, on the average for the season, by 25%. Before adjustment, daylight stem flow totals were consistently greater than lysimeterT values. After adjustment, the means differed by only 9%, and theRMSE was reduced from 129 to 69 g plant–1 d–1. The coefficient of variation of daylight stem flow totals increased throughout the season. In the glasshouse, method accuracy was comparable (errors < ± 10%) to what has been previously determined. In the field, determining method accuracy was confounded by plant-to-plant variability and, possibly, by errors, unique to the gauge design used in this study, at high flow rates. Thus, this method can provide accurate flow measurements from individual herbaceous plants and is a valuable technique for many applications.With 7 Figures  相似文献   

19.
Summary ?Progress in technology as well as signal processing has promoted Wind Profiler Radar (WPR) or sodar with RASS additions to become standard tools in profiling of the atmospheric boundary layer. Apart from these instruments’ basic abilities in profiling mean winds and temperature, this paper will give an emphasis on the profiling of ABL height as well as the turbulent fluxes of sensible heat and momentum both, with respect to methods as well as with respect to realization. The special focus will thereby be laid on the demands for vertical profiling, which were defined within the LITFASS-project of the German Meteorological Service. In the frame of this project, some special measuring campaigns have been performed where remote-sensing systems were used to assess their abilities in profiling ABL parameters. On the base of some case studies from these campaigns comparisons are shown, where results from sodar/RASS and WPR/RASS measurements are compared to measurements from airborne sensor systems and results from numerical models. Regarding turbulent heat fluxes, we found excellent agreement for remotely-sensed flux profiles from WPR/RASS with both, numerical models and airborne in-situ measurements. However, as the inherent errors of the remotely-sensed fluxes are in the order of ± 20 ⋯ 30 W/m2 typically, current signal processing does not allow to interpret small-scale vertical structures in the profiles with respect to surface inhomogeneities yet. Received June 16, 2001; revised February 20, 2002; accepted May 30, 2002  相似文献   

20.
Summary Observations of the diurnal (S 1) and semidiurnal (S 2) wind oscillations between 80 and 100 km show that their amplitudes are of the same magnitude as the mean winds. Both periods show pronounced seasonal changes in the same sense as, but much larger than would be expected from surface data forS 2, and in agreement with the idea of a thermal cause forS 1. From the observed wind oscillations the pressure oscillations can be computed. The pressure amplitudes are about 5 percent or, especially forS 2, more of the mean pressure, indicating a fifty to hundred-fold increase compared to the low atmosphere, as suggested by theory. But the phase ofS 2 does not show the expected reversal relative to the ground.S 1 seems to be much more regular than at the earth's suface where it is greatly disturbed by local influences. The few data on the lunar semidiurnal (L 2) oscillation show also the increse of the amplitudes with height.
Zusammenfassung Bestimmungen der ganztägigen (S 1) und halbtägigen (S 2) Windperioden in 80 bis 100 km Höhe ergeben Amplituden von derselben Größenordnung wie die mittleren Winde. Beide Perioden zeigen starke jahreszeitliche Schwankungen. FürS 2 wird das Maximum wie an der Erdoberfläche im Winter, das Minimum im Sommer erreicht; aber die jahreszeitliche Änderung ist in der Höhe viel größer. FürS 1 fällt das Maximum in den Sommer, wie man im Falle einer durch Erwärmung erzeugten Oszillation erwarten würde. Aus den beobachteten Windschwankungen können die entsprechenden Luftdruckschwankungen berechnet werden. Diese betragen 5 Prozent des mittleren Luftdruckes in diesen Höhen, oder besonders fürS 2 auch mehr, d. h. sie sind 50 bis 100 mal größer als am Erdboden. Eine derartige Zunahme mit der Höhe ist nach der Theorie zu erwarten. Die Phase vonS 2 zeigt jedoch nicht die erwartete Umkehr im Vergleich zu der Welle am Boden.S 1 scheint viel regelmäßiger zu sein als am Erdboden, wo es durch lokale Einflüsse sehr gestört ist. Die wenigen Daten für die halbtägige Mondgezeit (L 2) zeigen ebenfalls eine starke Zunahme mit der Höhe, die Phase ist aber ähnlich wie am Erdboden.
Résumé Les observations des oscillations diurnes (S 1) et semi-diurnes (S 2) du vent entre les niveaux de 80 km et 100 km au-dessus du sol indiquent que leurs amplitudes sont du même ordre de grandeur que leurs valuers moyennes. Ces deux périodes sont caractérisées par des changements saisonniers prononcés. PourS 2 ces changements bien que dans la même direction sont beaucoup plus considérables que ce que les données de surface nous porteratient à croire. PourS 1 ces changements sont en bon accord avec l'idée d'une cause thermique. Les oscillations de pression peuvent être obtenues à partir des oscillations observées du vent. Les amplitudes d'oscillation de la pression sont de l'ordre de 5 pour cent ou, spécialement dans le cas deS 2, plus encore des valuers moyennes de la pression. Ceci indique une augmentation de cinquante à cent fois par rapport à la basse atmosphère, fait d'ailleurs suggéré par la théorie. Toutefois la phase deS 2 ne présente pas d'inversion par rapport au sol.S 1 paraît beaucoup plus régulier qu'au sol où la situation sest fortement affectée par les influences locales. Les quelques données concernant les oscillations semi-diurnes (L 2) causées par la lune indiquent une augmentation des amplitudes avec l'altitude.

With 4 Figures

Dedicated to Dr.W. Mörikofer on the occasion of his 70 th birthday.  相似文献   

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