Dan Wu

Unlike previous studies from a single disdrometer, this study investigates and compares the raindrop size distribution (RSD) characteristics of convective inner‐rainband rain (CIR) and convective outer‐rainband rain (COR) in Typhoon Maria (2018), simultaneously captured for the first time by a newly established observational network including nine disdrometers in the northeastern Fujian Province of China. It is shown that the radar reflectivity for the CIR increases sharply with decreasing height below the melting layer, whereas it remains nearly unchanged for the COR. This suggests the dominance of collision‐coalescence process in the CIR, that is, the collection of small raindrops by larger ones as they fall. Thus, the surface‐level CIR generally has far lower concentration of small raindrops and larger mean raindrop diameter than those previously found in the COR. Close to the tropical cyclone (TC) eyewall, it is found for the first time that although the raindrops are relatively large, the raindrop concentration is too low to yield a high rain rate. In contrast, high rain rates are concentrated at a distance of about 1.5–2.5 times the radius of maximum wind from the TC center, where there are appropriate normalized concentrations (log₁₀N_w) and corresponding raindrop diameters. In addition, this study demonstrates differences between the CIR and COR in terms of the RSD evolution with increasing rain rate and the radar reflectivity–rain rate (Z‐R) and shape‐slope (μ‐Λ) relationships, confirming the existence of different rain microphysics in various rain regions of a TC.

The microphysical characteristics of rain may vary in different rain regions of a tropical cyclone (TC), but few studies have demonstrated the differences in raindrop size distributions (RSDs) of convective rain in different rainbands of a specific TC. This study examines the RSD characteristics and evolution of convective rain within outer rainbands and a coastal‐front‐like rainband associated with Typhoon Fitow, based on observational data from a disdrometer at Shibo station in Shanghai, China, during 6–7 October 2013. Considering the fast passage of convective TC rainbands over the disdrometer and the low rain rate of stratiform rain in the outer area, this study proposes a modified rain‐type classification method based on the disdrometer data. This study indicates that convective outer‐rainband rain (ORR) and coastal‐front rain (CFR) have different rain parameters, three parameters of the gamma model, radar reflectivity–rain rate (Z‐R), and shape–slope (μ‐Λ) relationships. The convective ORR has higher concentrations at all drop sizes than the convective CFR as well as larger spectral width, leading to the greater rainfall rate. The different Z‐R relationships suggest the necessity of a variable relationship for quantitative precipitation estimation (QPE) in different rain regions of the TC. This study also demonstrates for the first time that the RSD evolution with increasing rain rate is different in various convective rainbands associated with Fitow, suggesting that different microphysical parameterization schemes may be required for different rainbands in TC models.