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1.
Fernley Carney Skillen Cacciari & Janes 《Monthly notices of the Royal Astronomical Society》1998,293(3):L61-L64
We review the available observational data to show that the slope of the RR Lyrae MV –[Fe/H] relation is 0.18±0.03. The recent claim by Feast that, because of biases, the true slope is much steeper is not justified. 相似文献
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F. Pasian C. Vuerli D. Bisikalo A. Piskunov C. Cacciari Yu. Zaiko 《Experimental Astronomy》1997,7(4):377-384
The Science Operations Centre (SOC) for the Spectrum-UV project is expected to provide a number of services for the scientific community: support to observers, long-term correlation and trend analysis, analysis of the calibration observations, standard data processing, archiving, data retrieval and distribution. This paper provides an overall conceptual and architectural design of the Spectrum-UV SOC. 相似文献
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E. Carretta C. Cacciari F. R. Ferraro F. Fusi Pecci & G. Tessicini 《Monthly notices of the Royal Astronomical Society》1998,298(4):1005-1020
New BVI CCD photometry is presented for 60 RR Lyrae variables in the globular cluster M3. Light curves have been constructed and ephemerides have been (re)-derived for all of them. Four stars (i.e. V29, V136, V155 and V209), although recognized as variables, had no previous period determinations. Also, the period derived for V129 is significantly different from the one published by Sawyer-Hogg. Light curve parameters, i.e. mean magnitudes, amplitudes and rise times, have been derived. The discussion of these results in the framework of the stellar evolution and pulsation theories will be presented in a forthcoming paper. 相似文献
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Claudio Tomasi Stefano Marani Vito Vitale Frank Wagner Alessandra Cacciari Angelo Lupi 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):734-749
Measurements of direct solar irradiance were taken employing 4 different sun‐photometers at near infrared wavelengths, suitable for use in atmospheric hygrometry. This technique utilising a set of spectral ratios, in and out of selected water vapour absorption bands, was applied to the measurements to obtain accurate evaluations of precipitable water. For all the hygrometric ratios given by the 4 sun‐photometers used at the 3 stations of Sagres, Monchique and Mt. Foia, during the CLEARCOLUMN experiment, we determined the calibration curves by correcting them for the Rayleigh scattering effects and, then, plotting the natural logarithms of such corrected ratios versus the square root of the water vapour mass present along the atmospheric slant path. The regression lines drawn for the various scatter diagrams were estimated to give evaluations of precipitable water with an uncertainty of less than 5%, 3% and 10% at the 3 stations, respectively. The calibration curves of the sun‐photometer located at the Sagres station were determined using the precipitable water evaluations obtained from the local radiosounding measurements taken on 5 clear‐sky days. Those of the sun‐photometers used at the Monchique and Mt. Foia stations were instead determined through intercomparison between subsets of measurements simultaneously taken with various instruments at Sagres and Mt. Foia. Using these calibration curves, we examined all the field measurements determining the time‐patterns of precipitable water at the 3 stations. During the period from 16 June to 25 July 1997, precipitable water was found to vary between 1.1 and 3.7 g cm−2 at the Sagres station (with an accuracy within ±13%), between 1.0 and 2.8 g cm−2 at Monchique (±11%) and between 0.8 and 3.0 g cm−2 at the top of Mt. Foia (±26%). 相似文献
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Antonio Orsini Claudio Tomasi Francescopiero Calzolari Marianna Nardino Alessandra Cacciari Teodoro Georgiadis 《Atmospheric Research》2002,61(4)
Simultaneous measurements of downwelling short-wave solar irradiance and incoming total radiation flux were performed at the Reeves Nevè glacier station (1200 m MSL) in Antarctica on 41 days from late November 1994 to early January 1995, employing the upward sensors of an albedometer and a pyrradiometer. The downwelling short-wave radiation measurements were analysed following the Duchon and O'Malley [J. Appl. Meteorol. 38 (1999) 132] procedure for classifying clouds, using the 50-min running mean values of standard deviation and the ratio of scaled observed to scaled clear-sky irradiance. Comparing these measurements with the Duchon and O'Malley rectangular boundaries and the local human observations of clouds collected on 17 days of the campaign, we found that the Duchon and O'Malley classification method obtained a success rate of 93% for cirrus and only 25% for cumulus. New decision criteria were established for some polar cloud classes providing success rates of 94% for cirrus, 67% for cirrostratus and altostratus, and 33% for cumulus and altocumulus.The ratios of the downwelling short-wave irradiance measured for cloudy-sky conditions to that calculated for clear-sky conditions were analysed in terms of the Kasten and Czeplak [Sol. Energy 24 (1980) 177] formula together with simultaneous human observations of cloudiness, to determine the empirical relationship curves providing reliable estimates of cloudiness for each of the three above-mentioned cloud classes. Using these cloudiness estimates, the downwelling long-wave radiation measurements (obtained as differences between the downward fluxes of total and short-wave radiation) were examined to evaluate the downwelling long-wave radiation flux normalised to totally overcast sky conditions. Calculations of the long-wave radiation flux were performed with the MODTRAN 3.7 code [Kneizys, F.X., Abreu, L.W., Anderson, G.P., Chetwynd, J.H., Shettle, E.P., Berk, A., Bernstein, L.S., Robertson, D.C., Acharya, P., Rothman, L.S., Selby, J.E.A., Gallery, W.O., Clough, S.A., 1996. In: Abreu, L.W., Anderson, G.P. (Eds.), The MODTRAN 2/3 Report and LOWTRAN 7 MODEL. Contract F19628-91-C.0132, Phillips Laboratory, Geophysics Directorate, PL/GPOS, Hanscom AFB, MA, 261 pp.] for both clear-sky and cloudy-sky conditions, considering various cloud types characterised by different cloud base altitudes and vertical thicknesses. From these evaluations, best-fit curves of the downwelling long-wave radiation flux were defined as a function of the cloud base height for the three polar cloud classes. Using these relationship curves, average estimates of the cloud base height were obtained from the three corresponding sub-sets of long-wave radiation measurements. The relative frequency histograms of the cloud base height defined by examining these three sub-sets were found to present median values of 4.7, 1.7 and 3.6 km for cirrus, cirrostratus/altostratus and cumulus/altocumulus, respectively, while median values of 6.5, 1.8 and 2.9 km were correspondingly determined by analysing only the measurements taken together with simultaneous cloud observations. 相似文献
7.
O. Bendinelli C. Cacciari G. Parmeggiani F. Zavatti 《Astrophysics and Space Science》1983,95(2):393-400
The photoelectric brightness profiles inU, B, andV colors of the globular cluster NGC 362 are reported down to about 9 magnitudes below the central value, covering a radial distance of about 10 arc min. They were derived fromE-W scans, with a large rectangular diaphragm, giving the integrated profile of the cluster in about 6 min. of time. The inverse problem of determining the brightness profiles from integrated luminosities is solved by means of the regularization method. The agreement with the data available in literature (photoelectric brightness measurements in the inner 80 arc sec, bright stars distribution in the range 80-330 arc sec) is generally good. TheB-V andU-B radial color distributions are presented. It may seem that there is no color gradient, outside the central region dominated by red giants. 相似文献
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Aerosol remote sensing over land: A comparison of satellite retrievals using different algorithms and instruments 总被引：2，自引：0，他引：2
A.A. Kokhanovsky F.-M. Breon A. Cacciari E. Carboni D. Diner W. Di Nicolantonio R.G. Grainger W.M.F. Grey R. Hller K.-H. Lee Z. Li P.R.J. North A.M. Sayer G.E. Thomas W. von Hoyningen-Huene 《Atmospheric Research》2007,85(3-4):372-394
An inter-comparison study of the aerosol optical thickness (AOT) at 0.55 μm retrieved using different satellite instruments and algorithms based on the analysis of backscattered solar light is presented for a single scene over central Europe on October 13th, 2005. For the first time comparisons have been performed for as many as six instruments on multiple satellite platforms. Ten different algorithms are briefly discussed and inter-compared. It was found that on the scale of a single pixel there can be large differences in AOT retrieved over land using different retrieval techniques and instruments. However, these differences are not as pronounced for the average AOT over land. For instance, the average AOT at 0.55 μm for the area 7–12E, 49–53N was equal to 0.14 for MISR, NASA MODIS and POLDER algorithms. It is smaller by 0.01 for the ESA MERIS aerosol product and larger by 0.04 for the MERIS BAER algorithm. AOT as derived using AATSR gives on average larger values as compared to all other instruments, while SCIAMACHY retrievals underestimate the aerosol loading. These discrepancies are explained by uncertainties in a priori assumptions used in the different algorithms and differences in the sensor characteristics. Validation against AERONET shows that MERIS provides the most accurate AOT retrievals for this scene. 相似文献