排序方式： 共有16条查询结果，搜索用时 17 毫秒
1.
Heinz Lettau 《Boundary-Layer Meteorology》1990,50(1-4):1-9
The official report on this first comprehensive field experiment in boundary-layer meteorology was published 1957 in two volumes, edited by Lettau and Davidson (hereafter L&D). The official report is supplemented in this paper by relevant pre-history developments and a discussion of some selected post-history interpretations and follow-up experiments. 相似文献
2.
The term variangular is introduced to emphasize a significant difference between the present and certain earlier solutions to the problem of organized airmotion within the planetary boundary layer. The latter belong to the family of equiangular wind spirals and have the characteristic that the angle () formed by the vectors of shearing stress and geostrophic departure is invariant with height; it is shown that in this spiral-family, parabolic height-dependency of the effective (eddy) diffusivity (K) alone is permitted, including the asymptotic case of constant K; the famous Ekman spiral as well as the Rossby spiral are two prominent members of the family of equiangular wind spirals. The new variangular theory, as the name implies, permits variation of with height (z) and produces more versatile profiles of wind and stress due to less restraint in K (z). As an example of comparison with observed data, monthly mean wind profiles obtained at Plateau Station, Antarctica, are selected since they exhibit a noteworthy degree of variangularity, in relatively satisfactory agreement with properties of the new theoretical model for wind spirals.National Research Council Visiting Scientist Research Associate, Regional Environments Division, Earth Sciences Laboratory. 相似文献
3.
Wind and temperature profile prediction for diabatic surface layers including strong inversion cases
Heinz H. Lettau 《Boundary-Layer Meteorology》1979,17(4):443-464
The micrometeorological research program in Antarctica has provided extensive data on wind and temperature profile structure under strong to extreme inversion conditions (Dalrymple et al., 1966; Lettau et al., 1977). The basic similarity hypotheses and limiting conditions for prediction of diabatic surface layer profiles are summarized. The model by Businger et al. (1971) for dimensionless shear and temperature gradients is revised to conform with the new results for strong stability. A novel similarity hypothesis is introduced to complete the step from shear and gradient prediction to prediction of absolute wind speed, wind energy, and temperature on the basis of prescribed external factors of surface layer structure. The physics of interactions between predicted profile tilting and curving are discussed and used to explain several micrometeorological paradoxes, including that of the elevated minimum of air temperature observed occasionally near the active surface when the energy budget is of the nocturnal type. 相似文献
4.
H. Lettau 《Boundary-Layer Meteorology》1977,12(2):213-229
Monthly averages of the surface energy balance are parameterized, resulting in a reduced solar forcing function and a non-dimensional time scale for computing the thermal response at the air/snow interface by numerical forward integration. The climatonomic transform of the balance equation serves to assess surface-temperature perturbations resulting from parameter modifications which simulate effects of dust contamination of a snow surface. Three climatonomical model experiments permit the following conclusions: (1) an albedo reduction increases primarily the summer temperatures; (2) an emissivity decrease raises the temperature of all months nearly uniformly; (3) the thermally induced feedback on submedium structure (if summer melting is instigated) increases the storage capacity and reduces spring and summer temperatures with compensating rise in autumn and winter temperature. Quantitative results are exemplified by assumed modification of conditions known to exist at the South Polar Plateau. 相似文献
5.
Under the assumption of a geostrophic wind varying exponentially with height, profiles of four turbulence characteristics (Reynolds stress, eddy diffusivity, momentum mixing length, and energy dissipation rate) are evaluated for three cases of quasi-steady wind profile observations under near-neutral boundary layer conditions. These cases occurred during the Wangara Experiment organized by CSIRO at Hay, N.S.W., Australia, in 1967. It is shown that mean vertical motion and surface friction velocity significantly influence the evaluated profiles of the turbulence characteristics.This study was done while Zhang visited the Department of Meteorology, University of Wisconsin, from the Department of Meteorology, Nanjing University, China, and was completed when Zhang was affiliated with the National Center for Atmospheric Research.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
6.
Heinz Lettau 《Meteorology and Atmospheric Physics》1954,7(1):133-157
Production and expenditure rates in the terrestrial budget of various air properties (mass of precipitable water and carbon dioxide, zonal and root mean square momentum, heat, and entropy) are studied. The discussion is based on graphs and diagrams which illustrate the global radiation and heat budget, dynamical energy forms and conversions, hydrologic and carbon dioxide cycles, and meridional cross sections of mass, momentum, heat, and entropy budget terms. A comparison of atmospheric property holdings with expenditure rates results in a fictitious interval of time required to annull the holdings. For momentum, precipitable water, and heat this interval of time has the order of magnitude of 100, 101, and 102 days, respectively.
With 8 Figures. 相似文献
Zusammenfassung Es werden die Einnahme- und Ausgabeposten beim terrestrischen Haushalt verschiedener Eigenschaften der Luft (Wasserdampf und Kohlensäure als Beispiele von Masseneigenschaften, ferner zonal-vektorieller und skalarer Impuls, Wärme und Entropie) untersucht. Die Diskussion wird durch graphische Darstellungen und Diagramme unterstützt, welche folgende Größen veranschaulichen: den globalen Strahlungs- und Wärmehaushalt, dynamische Energieformen und ihre Umwandlungen, Wasserkreislauf und Kohlensäurekreislauf, sowie Bilanzposten der Massen-, Impuls-, Wärme- und Entropiebilanz in Meridionalschnitten. Eine Vergleichung des Gehalts der Atmosphäre an verschiedenen Eigenschaften mit ihren Verlusten liefert ein fiktives Zeitintervall, in welchem die Reserven aufgebraucht würden, wenn kein Ersatz nachgeliefert würde; die Größenordnung dieses Zeitintervalles ergibt sich zu 100, 101 und 102 Tagen für Impuls, Wasserdampf und Wärme.
Résumé L'auteur étudie la production et la dépense dans le bilan terrestre des différentes propriétés de l'air (la vapeur d'eau et le dioxyde de carbone comme exemples de propriétés de masse, puis la quantité de mouvement zonale-vectorielle et scalaire, la chaleur et l'entropie). Des graphiques illustrent la discussion qui représentent les grandeurs suivantes: économie globale de la radiation et de la chaleur, formes dynamiques de l'énergie et leurs transformations, cycles hydrologique et du dioxyde de carbone, ainsi que les composantes du bilan des masses, de la quantité de mouvement, de la chaleur et de l'entropie en coupes méridionales. La comparaison du contenu des diverses propriétés dans l'atmosphère avec leurs pertes est fournie par un intervalle de temps fictif, pendant lequel les réserves seraient épuisées, au cas où leur renouvellement ferait défaut; l'ordre de grandeur de cet intervalle résulte à 100, 101 et 102 jours respectivement pour la quantité de mouvement, la vapeur d'eau et la chaleur.
With 8 Figures. 相似文献
7.
8.
9.
Heinz H. Lettau 《Boundary-Layer Meteorology》1974,6(1-2):13-33
Conventional theory predicts that in the layer of frictional influence, the semi-diurnal forcing by pressure-gradient oscillations should produce responses in air motion which show reduced amplitude and phase-leading, in comparison with frictionless conditions in the free troposphere. Wind-profile data obtained by anemometers on a floating mast during the ‘1965-Atlantic Meteor Expedition’ at an anchor station in the SE-trade-wind regime near the equator showed that the amplitude of the west component at the 4-m level practically equalled the fr ictionless value, while other measurements gave evidence of frictional effects, such as phase-leading, and vertical shear from 1 to 10 m. The observed wind response is explained by dynamic coupling as a consequence of forcing by the horizontal pressure gradient oscillation and resulting semi-diurnal variation of surface stress and therefore of eddy diffusivity. 相似文献
10.
Dr. W. Ehrismann Dipl.-Geophys. H. -J. Götze Dipl.-Geophys. W. Leppich Dipl.-Geophys. O. Lettau Prof. Dr.-Ing. O. Rosenbach Dipl.-Geophys. W. Schöler Univ.-Prof. Dr. P. Steinhauser 《International Journal of Earth Sciences》1976,65(1):767-778
Gravity measurements in the Krimmler Ache Tal and Obersulzbachtal (Oberpinzgau/ Austria) have been carried out. The results of the measurements are presented as follows:
- Profiles of Bouguer anomalies (BA),
- Profiles of regional and residual anomalies.