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1.
C. O. Oluwafemi 《Pure and Applied Geophysics》1983,121(5-6):1065-1076
Solar, sky, and aureole radiance data from Kensington, Australia, and Lagos, Nigeria, are analysed. The values of the aerosol
optical thickness at Lagos are comparable to measured values elsewhere in the subregion (Abidjan) under light haze. The values
at Kensington are close to those of the “background aerosol.” Identical and anomalous values of aerosol optical thickness
occurred at 1.67 μm at both stations as less than 15% of the values can be accounted for by aerosols. The high optical depths
are therefore explained in terms of absorption, possibly mainly by CO2 (59–65%) and, to a lesser extent, by H2O (20–26%). Following correction for molecular multiple scattering, the aerosol scattering phase function increases substantially
at 0.5 μm in Kensington and decreases considerably at 0.76 μm in Lagos when compared to the uncorrected function, confirming
the relative fineness of the Kensington aerosol. The Lagos aerosol size distribution for moderately dusty air is reasonably
bimodally log-normal with modal radiusr
m=0.49 μm (1.36 μm) for the moder≤1 μm (r>1 μm). The Kensington aerosol resembles one withr
m=0.05 μm forr<1 μm. There the Born approximation appears appropriate, and the weighted mean square radiusp
2=0.13 μm2. In the near forward direction the aerosol scattering phase funciton for Lagos resembles Deirmendjian’s simulations for a
silicate-L haze and, for Kensington, a silicate-H haze. 相似文献
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Data from the Tropical Rainfall Measuring Mission (TRMM) satellite sensors, the Microwave Imager (TMI, 3A12 V6) and other satellite sources (3B43 V6) have been used to derive the thunderstorm ratio β, total rain accumulation M, and 1-min rainfall rates, R1min, for 37 stations in Nigeria, for 0.001–1% of an average year, for the period 1998–2006. Results of the rain accumulations from the TRMM satellite (1998–2006) were compared with the data collected from 14 ground stations in Nigeria for the period 1991–2000. The two data sets are reasonably positively correlated, with correlation coefficients varying from 0.64 to 0.99. Deduced 1-min rainfall rates compared fairly well with the previous ground data of Ajayi and Ezekpo (1988. Development of climatic maps of rainfall rate and attenuation for microwave applications in Nigeria. The Nigerian Engineering 23(4), 13–30) with correlation coefficients varying from 0.17 to 0.97 in all 37 stations. The agreement was much better when compared with the International Telecommunications Union Radio communication Study group 3 digital maps with correlation coefficients varying from 0.84 to 0.98 in 23 locations; however there were negative correlation coefficient (of 0.2 in 7 stations) in the Middle Belt and a weak positive coefficient (of 0.09 in 6 stations) in the South South. Regionally the inferred mean annual 1-min rainfall rates are the highest in the South-East region with values between 111 and 125 mm/h throughout the 9 years, followed by the South-South region (105–124 mm/h). The lowest rainfall rate and rainfall accumulation occur in the North-West region (60–86 mm/h) followed, in ascending order, by the North-East (66–95 mm/h) region, the Middle-Belt region (76–102 mm/h) and the South-West region (77–110 mm/h). The present results were also compared with 9 tropical stations around the world and there was positive correlation between the results. The present results will be very useful for satellite rain attenuation modeling in the tropics and subtropical stations around the world.It is useful to note that one country, particularly one as large as Nigeria, can have significant variations in its rainfall characteristics for a variety of reasons, and this is borne out by the results presented. 相似文献
4.
C. O. Oluwafemi 《Pure and Applied Geophysics》1980,118(2):775-782
Solar radiance measurements covering over seventeen months are analysed for a location beside the Lagos Lagoon. The aerosol extinction coefficient was generally higher in the dusty months than in the wet months. Clean air estimates of the coefficient are made. Data on its wavelength dependence are also presented. 相似文献
5.
C. O. Oluwafemi 《Pure and Applied Geophysics》1980,119(4):831-840
Helicopter measurements of solar irradiance and meteorological data within the atmospheric boundary-layer were made in Lagos during February 1979. Filter samples of aerosols were collected both during flight in February 1979 and at ground level in December 1978. Profile data on spectral aerosol optical depth were obtained and, from these, the aerosol extinction coefficient at two wavelengths (0.5 and 0.88 m) were calculated. Precipitable water was low and was contained mainly within the 750 m layer above ground, suggesting the establishment of a deep unstable boundary layer. Calculated channel energy depletions by aerosols show that, within the first 750 m of the surface, the 0·88 m might be more efficient at attenuating solar energy than 0·5 m. The lagoon (maritime) aerosol sample indicated a more monodisperse size-distribution than the dusty harmattan aerosol sample. 相似文献
6.
Power spectral and cross-spectral studies of atmospheric electrical parameters for different months of the year are presented. The data represent fair weather conditions and the frequency range is from 0.01 to 0.3 cph. The analysis shows spectral peaks in the atmospheric electric parameters for frequencies corresponding to the diurnal wave; in many cases large variances are noted for the frequencies 0.083, 0.125 and 0.17 cph. Annual cycles in the spectra are also observed. In general, fairly small variances are obtained for frequencies above 0.05 cph. High coherences for the atmospheric electric parameters are observed in the lower frequency part of the spectra and in some cases in other parts as well (i.e., 0.083, 0.125 and 0.17 cph). Phase relationships of the electric components are also presented. 相似文献
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This paper investigates the motion of a test particle around the triangular equilibrium points under the effects of radiation pressure of the second primary and its Poynting–Robertson (P–R) effect when the first primary is an oblate spheroid. It is seen that triangular points are influenced by the presence of these parameters: radiation pressure from the secondary and the incidental P–R effect and the oblateness of the first primary. The linear stability of the problem is studied and applied to the binary system RXJ 0450.1-5856, the triangular points are unstable due to positive roots in the Lyapunov sense when P–R effect is considered as against their conditional stability in the absence of P–R drag effect. 相似文献
9.
Abstract factor analyses were performed on databases consisting of simulated samples from aqueousequilbria.The program COMPLEX was used to generate equilibrium species in a system of three reactantmetals and five reactant bases.Reactant concentrations and pH were drawn from random-normaldistributions so that sample data vectors comprised a multivariate log-normal distribution of equilibriumconcentrations.In addition,sample groups were created containing different distributions for pH andreactant concentrations.Equilibrium species were shown to contain variance contributed by change in pH among samples aswell as change in reactant concentrations.Factor modelling revealed the qualitative relationships amongthe species and how the relationships change with pH.Factors also revealed those reactants containingvariance in the data matrix.In some cases,reactant variance obscured relationships between pH and theequilibrium species.Since factor modelling of a simulated data matrix revealed the expected chemical equilibriuminteractions,a potentially powerful tool exists for investigating the effects of outliers and error. 相似文献
10.
The influence of micrometeorological parameters (wind speed, temperature stratification and atmospheric stability) upon electric polar conductivity, potential gradient, vertical total current density and vertical convection current density is studied by means of power spectral and coherence spectral analysis. The analyses show great variations in the atmospheric electric parameters for frequencies corresponding to the diurnal wave (0.042 cph) and in many cases great variances are noted for the frequencies 0.083, 0.125 and 0.17 cph. The influence of the micrometeorological parameters upon atmospheric electricity seems to be significant for these frequencies. Annual changes of the power and coherence spectra are also observed. 相似文献