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1.
N. M. Zoumakis 《Il Nuovo Cimento C》1992,15(2):247-250
Summary An approximate relationship between the gradient, Ri, and the bulk Richardson number, Rib, for unstable atmospheric conditions, is suggested. The proposed relation shows much better agreement with the estimation
provided by a numerical iterative method than the usual approximations suggested by Louis and Byun. 相似文献
2.
G. Cevolani 《Il Nuovo Cimento C》1991,14(2):203-206
Summary Time variations of the semi-diurnal and diurnal tides observed at Budrio (45°N, 12°E) in the wind structure of the lower thermosphere
((80÷110) km) throughout the period 1976–1990 are herewith represented as monthly contours of both amplitudes and phasesvs. height. The semi-diurnal tide has more marked seasonal variations, showing amplitudes generally larger than the diurnal
ones ((10÷30) m/svs. (5÷15) m/s). The vertical wavelengths are longer in summer than in winter, at least below 100 km. Agreement with new numerical
models for semi-diurnal tide at 50°N appears to be satisfactory. 相似文献
3.
Detection of urban heat island in Istanbul, Turkey 总被引:1,自引:0,他引:1
《Il Nuovo Cimento C》1995,18(1):49-55
Summary The aim of this study is to detect the urban-heat-island effects in Istanbul which is the largest and most important megapolis
of Turkey. The mean monthly minimum, normal and maximum temperatures are derived from daily ones. The method of linear regression
and Mann-Kendall test are used in the analysis of trend. Despite Istanbul is surrounded by the Black Sea and Marmara Sea,
the urban-heat-island intensity stands out quite clearly. 相似文献
4.
Summary The analysis of daily precipitation data at many weather stations in Alpes and Po Valley gives evidence of a “tidal” influence
from luni-solar gravitational fields. Periodicities in the 13–15 and 27–30 day time interval have been frequently extracted
from data series (ENEL data: 1970–1981 years; SMR data: 1961–1980 years), by using distinct methods. The tidal influence does
not appear to be strictly constant with time, as the possible result of a modulation effect of luni-solar cycles having similar
periods. Time variations of daily precipitation data as a function of some particular cycles show that gravitational tides
affect heavy rainfalls more than mean precipitation values. The different contribution of “semi-monthly” oscillations with
season underlines a more distinguishable regime of vertical motions in Winter with respect to Summer. In investigating joint
effects of different luni-solar components, the inverse Fourier transform method points out superimposed influences in correspondence
to some years (1966 and 1976), climatologically very interesting, and this might assist in the previsional studies of extreme
precipitation.
Riassunto I risultati delle analisi dei dati giornalieri di precipitazione, raccolti presso molte stazioni dell'arco alpino e della pianura padana (dati ENEL: anni 1970–1981 e dati SMR: anni 1961–1980) mettono in mostra un'influenza ?mareale? dei campi gravitazionali luni-solari. Anche utilizzando metodi distinti, è solitamente evidenziata la presenza di componenti periodiche nelle finestre temporali di 13–15 e 27–30 giorni. L'effetto mareale non appare rigidamente costante nel tempo, potendo risultare dalla modulazione di cicli luni-solari aventi periodi simili. Le variazioni nel tempo dei dati giornalieri di precipitazione in funzione di alcuni cicli particolari mostrano che l'influenza mareale ha un effetto maggiore sulle precipitazioni piú forti che non sui valori medi di precipitazione. Il diverso contributo di componenti ?semi-mensili? con la stagione sta ad indicare che l'azione di marea è meglio identificabile in inverno che non in estate. Nelle indagini sugli effetti congiunti di differenti componenti luni-solari, il metodo dell'antitrasformata di Fourier rivela influenze sovrapposte nel campo delle precipitazioni soprattutto in corrispondenza di alcuni anni particolarmente interessanti sotto il profilo climatologico (anni 1966 e 1976), e in tal senso questo metodo può essere utile in studi previsionali delle precipitazioni piú forti.相似文献
5.
Summary In order to improve the simulation of wind probability distributions at ground level, eight years of wind data of the multivariate
analyses at 850, 700, 500 hPa levels over Italy, and eleven years of wind radiosoundings performed at 5 Italian Air Force
stations at 950, 900, 800, 700, 600, and 500 hPa have been processed. The vertical profiles of the distribution parameters
of wind speed present predictable behaviour, with the exception of Brindisi. The frequency distribution profiles of the wind
directions are more complex.
Temporarily seconded to the RISOE National Laboratory (DK) as part of the EEC-DGXII Programme ?Stimulation Action?. 相似文献
6.
Summary In a recent note by Shepherd it is claimed that the main conclusions discussed in a paper by Petroniet al. about certain instability mechanisms for steady equivalent barotropic flows are incorrect and, although no criticism is made
regarding the analytical treatment, two counterexamples are presented to support this thesis. In addition to this it is asserted
that the envisaged necessity for energy and enstrophy to be transferred in both spatial directions in a normal-mode instability
is ?extremely well known?. Here we demonstrate that Shepherd's conclusions are without foundation and confirm the validity
and originality of Petroniet al. results by showing that:a) the first counterexample describes a situation that is in fact provided for by Petroniet al.'s analysis;b) the second counterexample is not dynamically realizable and, even if it were, the related conclusions would not apply to
flows defined in doubly periodic or bounded domains such as those considered by Petroniet al.; c) the mechanism cited above is not known at all in the specific context dealt with by Petroniet al. We emphasize this by pointing out that for steady equivalent barotropic flows the range of parameters for which such an instability
mechanism is allowed complements exactly the range for which the steady states are stable according to Benziet al. 相似文献
7.
Summary The determination of the Earth's surface temperature from satellite radiometric measurements in the (10.5÷12.5) μm spectral
range is affected by an atmospheric error, mainly caused by aerosol particle extinction and water vapour absorption. The temperature
deficit is usually defined as the difference between the actual surface temperature and the equivalent brightness temperature
obtained from satellite measurements. Neglecting the errors due to the assumption of unity surface emittance, this temperature
deficit was calculated for ten different atmospheric models, with and without water vapour absorption. The results show that
the temperature deficit produced by aerosol particles, carbon dioxide and other minor gases gradually increases, on the average,
from 0.8 to 1.2 K as one passes from cold to warm air conditions of the atmosphere. The temperature deficit produced by atmospheric
water vapour was found to range from about 0.1 K in the midlatitude winter model to 4 K in the tropical model. Analysis of
the results shows that temperature deficit may be subject to wide variations, which are closely related to the seasonal and
meteorological conditions of the atmosphere.
Paper presented at the 1° Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome. 相似文献
8.
P. Y. Zhu 《Il Nuovo Cimento C》1991,14(3):263-283
Summary The effective-medium approximation is applied to investigate scattering from a half-space of randomly and densely distributed
discrete scatterers. Starting from vector wave equations, an approximation, called effective-medium Born approximation, a
particular way, treating Green's functions, and special coordinates, of which the origin is set at the field point, are used
to calculate the bistatic- and back-scatterings. An analytic solution of backscattering with closed form is obtained and it
shows a depolarization effect. The theoretical results are in good agreement with the experimental measurements in the cases
of snow, multi- and first-year sea-ice. The root product ratio of polarization to depolarization in backscattering is equal
to 8; this result constitutes a law about polarized scattering phenomena in the nature. 相似文献
9.
Summary The results of local meteorology, solar radiation and ground-level ozone measurements taken in Antarctica during the second
Italian expedition (December 86–February 87) at Terra Nova Bay are presented. During the summer months the site of the Italian
base camp is characterized by a thin strip of deglaciated ground, along which the temperature measurements close to the ground
and up to 6 m high show a strongly superdiabatic profile. This irregular trend of the temperature in the surface layer is
mainly due to the notable incoming amounts of radiation and to the extreme transparency of the atmosphere. This is also shown
by the low values of the ratio between total radiation and diffuse radiation. The ground is thus subjected to intense heating,
especially in the warmer hours of the day, while the surface layer of the atmosphere will be characterized by strong upward
heat fluxes and by turbulent convective movements. Vertical-temperature-profile measurements show an almost forced persistence
in the superdiabatic trend, which tends towards isothermic values only as a resultof rapid variations in the direction and
intensity of the wind, connected to the downward flux of cold air masses, shown also by the simultaneous increases in ground-level
ozone concentrations which would support the presence of dry-deposition processes in the lower layer. However, the complex
local orography and the horizontal discontinuity (sea, deglaciated coast, snow-covered surfaces) do not permit a correct application
of profile flux relations, normally used in studies on groundlevel dry-deposition.
Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome. 相似文献
10.
Summary Global average temperatures from 1860 to 1989 were analysed with a simple fitting procedure. The temperature records can be
fitted with a rising exponential up to 1946 and with the same exponential minus an increasing cooling action from 1946 to
1989. It is shown that the results are compatible with the hypothesis of an albedo increase caused by SO2 emissions. This hypothesis gives satisfactory explanations of the temperature drop in the years 1940–1970, of the different
warming of the northern and southern hemispheres and of the slower warming observed over North America. The results give an
indication that the greenhouse warming in the next years could be faster than predicted until now.
Due to the relevance of its scientific content, this paper has been given priority by the Journal Direction. 相似文献