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Showing papers on "Disdrometer published in 1988"


Journal ArticleDOI
TL;DR: In this paper, the effects of both statistical fluctuations and physical variations are simulated for an S-band radar for backscatter from rain media, which is characterized by a gamma model of the raindrop size distribution (RSD).
Abstract: Fluctuations in the radar measurements of ZDR are due to both signal power fluctuations and the cross-correlation between the horizontal and vertical polarized signals. In Part I of this study, these signals are simulated for an S-band radar for backscatter from rain media, which is characterized by a gamma model of the raindrop size distribution (RSD). The parameters N0, D0, m of the gamma RSD are then varied over the entire range found in natural rainfall. Thus, the radar simulations contain the effects of both statistical fluctuations and physical variations. We also simulate sampling of raindrops by disdrometer. The sampling errors are related to the Poisson statistics of the total number of drops in the fixed sample volume and to the statistics that govern the gamma distribution of drops as a function of size. We simulate disdrometer RSD samples over the entire range of N0, D0, m values found in rainfall, so that the effects of statistical fluctuations and physical variations are introduced....

48 citations


Journal ArticleDOI
TL;DR: In this paper, the relationship between X-band specific attenuation (A, Z, and ZDR) and disdrometer raindrop spectra was investigated using both disDrometer and radar data.
Abstract: In Part II of this study, simulations of multiparameter radar observables to include X-band specific attenuation (A) are performed in order to study the relationship between A, Z, and ZDR. We also compute the triplet (A, Z, ZDR) from simulations of disdrometer raindrop spectra. As in Part I, our simulations include the fluctuations due to both measurement errors and physical variations of the gamma raindrop spectra parameters (N0, D0, m). We examine the correlation between (A/Z) and ZDR derived from both disdrometer and radar simulations, and show that the disdrometer-based data yields a negative collation (∼ −0.9) between (A/Z) and ZDR, whereas for radar data the correlation ≈ 0. We emphasize that these correlations are due only to measurement fluctuations, and not to physical variations. The large magnitude for the negative correlation compresses the scatter in plots of (A/Z) versus ZDR based on disdrometer RSD samples whereas the same scatter plots using multiparameter radar data show very lar...

30 citations


Journal ArticleDOI
TL;DR: In this paper, up-and down-link attenuation were simultaneously measured at 30/20 and 14/12 GHz for more than 10 rainfall events from 1979 to 1981 with two Japanese geostationary satellites, Communication Satellite (CS) and Broadcasting Satellite for Experimental Purposes (BSE).
Abstract: Up- and down-link attenuations were simultaneously measured at 30/20 and 14/12 GHz for more than 10 rainfall events from 1979 to 1981 with two Japanese geostationary satellites, Communication Satellite (CS) and Broadcasting Satellite for Experimental Purposes (BSE). Statistical analyses of the ratio of up-link attenuation to down-link attenuation, the “attenuation ratio,” show that attenuation ratios of both CS and BSE do not necessarily agree with theoretical values assuming the Marshall and Palmer raindrop size distribution and that attenuation ratios vary widely from one event to another. Raindrop size distributions measured by a disdrometer are employed for the analysis of measured attenuation ratios. It is found that disdrometer-derived attenuation ratios agree well with measured ones for BSE but that the agreements are not so good for CS. A model calculation of bright band attenuation and a data analysis with rain type classification suggest that the above discrepancy between measured and disdrometer-derived attenuation ratios is caused by bright band attenuation. It is concluded that disdrometer data are useful for the estimation of slant path attenuation ratio for the heavy rainfall rate range.

10 citations


Journal ArticleDOI
TL;DR: In this paper, the first results of the analyses are presented, focusing on the variation characteristics of the precipitation type (thunderstorm and widespread) as well as to the variations of the distributions in short time intervals, that may be caused by different effects, for example the growth and decay of a precipitation cell or the movement of a cell combined with the different fall velocities of small and large drops.
Abstract: The knowledge of raindrop size distributions is of great interest to cloud physicists, radar meteorologists and communication engineers. Beginning from the Winter 1986–87, the Precipitation Group of the Atmospheric Physics Institute installed on the roof of the Institute building in Roma-Eur a disdrometer RD-69. The sensor is an electromechanical device with surface of 50 cm2 able to measure the raindrop diameter with a precision of 5% and a resolution (delay between two drops hitting the sensor) of one millisecond. After the calibration, significant precipitations were recorded continuously, with a sample period of 1 minute, during the whole life of the storms. It can be expected that a knowledge of the drop size distributions, and in particular of the differences between distrubitions, can be used to infer details of the storm and the environment. In this work the first results of the analyses are presented. Particular attention was conferred to the variation characteristics of the precipitation type (thunderstorm and widespread) as well as to the variations of the distributions in short time intervals, that may be caused by different effects, for example the growth and decay of a precipitation cell or the movement of a cell combined with the different fall velocities of small and large drops.

2 citations