| Rain drop size distribution (DSD) is used to describe the raindrop spectral of all kinds of diameter per unit volume. Our research work is focus on two aspects. The first is about developing an instrument, based on a plane sound box, to detect the raindrop size distribution. The second is about the analysis of the raindrop size distribution data observed by the DISDROMETER instrument.The plane sound box is used as the sensor to detect the size and the number of raindrops. There are seven kinds of water-drop diameter (1.13, 1.24, 1.31, 1.46, 1.50, 1.60, and 2.33 mm) falling from different heights on the plane sound box, which can produce the oscillation signal. According to the equal-momentum principle, the regression relation between the diameter of the water-drop and the amplitude of the signal can be established. Then the values of the all kinds of raindrop diameters are put into the equation, the value of amplitudes of the corresponding signal can be obtained. In the end, the table of the raindrop diameters and the signal amplitudes are obtained.Some factors, which can cause the measurement errors of the instrument, such as the water on the plane sound box and the oblique position are also analyzed in the laboratory experiments. When there exists water on the instrument, the amplitudes are not stable. The oblique position of the instrument can make the water slide off the instrument. But the amplitudes become weaker for the oblique position. In the laboratory experiment, it make sure that the 30 angle is satisfied.At last, an instrument, having 2-channel and 2-box with an area of 258.56 cm2 is designed.The DISDROMETER can measure the raindrop number in 20 intervals of diameter. The data analysis includes two steps. The first is the comparison between the DISDROMETER and the raindrop-paper measurements. The second is focused on the analysis of the DISDROMETER data in 5 aspects. The comparison experiments between the DISDROMETER and the raindrop-paper is for the DISDROMETER's validation. Three precipitation cases, i.e., on May 25, 2004, on June 16, 2004 and on September 14, 2004, are taken for the validation. The two kinds of spectral agree with each other for most diameter intervals, but the number of small drops (≤0.75mm) measured by the raindrop-paper is much larger. The reason is that the underestimate of the small raindrops for the DISDROMETER and the overestimate of the small raindrops for the raindrop-paper. The coefficient of the two kinds of rain-rate R (or the radar reflectivity Z) is from 0.837 to 0.8408(from 0.8367 to 0.8546). Moreover, the R's ( or Z's) time trends are similar and both the amplitudes are similar, too. All these comparison analyses prove that the data from DISDROMETER are reliable.The analyses of the DISDROMETER data have 5 contents.The first is to estimate the function of the raindrop size distribution. The M-P function and the Gamma function are used to describe the distribution. For the stratiform rainfall, both the two kinds of functions do very well, with correlation coefficients more than 0.9. However, for the convective rainfall, the Gamma function does better than the M-P function. When the double-Gamma is used to describe the raindrop size distribution, the result shows that it is better than the Gamma function.The second is to analyze the characteristics of the equilibrium and the non-equilibrium raindrop size distribution. The mean values of all kinds of diameters (such as the mean diameter Dm, the mode diameter Dd, the mean volume diameter Dv, the predominant diameter Dp, the median diameter Dnd and the median volume diameter Dn ) of the equilibrium raindrop size distribution are higher than those of the non-equilibrium. However, the standard deviations of the all kinds of...
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