We have measured vertical profiles of DSD using 443 MHz wind profilers at Tsukuba and Okinawa, Japan. In the estimation of DSD, we have applied an iterative retrieval technique involving repeated convolutions. This technique assumes no particular shape of DSD and can be used to derive detailed raindrop size distributions. It, therefore enables small changes of DSD with altitude to be observed. Results show that significant vertical variations of DSD appear during fall of raindrops. We have calculated various integral parameters from the derived DSD, such as reflectivity factor Z, total number of raindrops N, second moment, and median volume diameter D0. Reflectivity factor correlates well with rain rate R, which is in agreement with previous studies. The second moment depends strongly on R and is also linearly related to NT. Physically, the second moment is related to the total surface area of raindrops. The probability of drop collision is proportional to the square of the drop size. This may lead to the strong relation between R and S. Statistically, no apparent correlation is shown between R and D0, as in previous studies. Vertical profiles from one event, however, show a clear inverse relationship between N to D0. Many profiles of N and D0, interestingly show the similar inverse relations. These systematic features are useful for the improvement of our understanding the rain formation process, the evaluation of the TRMM PR and the development of rainfall-estimate algorithms for the dual-frequency radar planned on board the GPM.