Rainfall Intensity and Raindrop Spectrum for Different Parts in Landing Typhoon Matmo

During typhoon Matmo passage over Fujian from 23 Jul to 25 Jul in 2014, it passes through two disdrometer sites: Pingnan and Youxi. Pingnan site locates in eastern Fujian that represents the heavy rain region of typhoon Matmo, and Youxi site represents the middle path region of typhoon Matmo moving. Thus, microphysical characteristics of raindrop size distribution in different parts of typhoon Matmo are studied through the PARSIVEL2 disdrometer measurements at these two sites. The evolution of raindrop size distribution parameters reveals different segments of the storm, that the fluctuation of rainfall intensity in the right part is stronger than those in the middle. Heavy rainfalls happen in right front side, rear side of outer rainband and residual cloud. There is showery in the outer rainband in which rainfall intensity fluctuate frequently. Approaching to the central region of typhoon Matmo, the precipitation becomes more continuous and rainfall intensity changes more smoothly. In the right side rainband, the spectral width of raindrop size distribution changes from wide to narrow, the concentration of small rain drops increases at first and then decreases, and concentration of large rain drops decreases gradually. In the middle path of typhoon Matmo, the concentration of small rain drops increases first and then decreases, but spectral width of raindrop size distribution and concentration of large rain drops suddenly rise for difference. The evaluation of raindrop concentration and liquate water has some certain relations to the changed rainfall intensity, but degrees of their changes are not in tune. When rainfall intensity is less than 10 mm·h^-1, a large number of small droplets contribute to the precipitation. The contribution to rainfall intensity by large number of small raindrops is higher in the right side rainband than in the middle moving path. In the central region of typhoon Matmo, the contribution by high concentration of small raindrops to the rainfall intensity is higher than in front side and rear side rainband. On the contrary, when rainfall intensity is higher than 10 mm·h^-1, the heavy rainfall in front outer rainband and residual cloud are the direct appearances by concentration growing of large droplets. The precipitation at Pingnan is more unstable than that at Youxi, so more fiercely collision broken processes lead to raindrop concentration repeating with droplets growing in right part of typhoon Matmo. Parameters of μ and λ meet the linear function both at 2 sites. Linear fit functions can be used to reduce Gamma distribution function, getting good results. The μ and λ have wide distributions in the region less than 10 mm·h^-1. However, when rainfall intensity is more than 10 mm·h^-1, parameters of μ and λ decrease with rainfall intensity increasing, and vary with rainfall intensity related to the region and precipitation types.