Drop Size Distribution Characteristics of Seven Typhoons in China

Abstract

This study is the first attempt to investigate the characteristics of the drop size distribution (DSD) and drop shape relation (DSR) of seven typhoons after making landfall in China. Four typhoons were sampled by a C-band polarimetric radar (CPOL) and a two-dimensional video disdrometer (2DVD) in Jiangsu Province (East China) while three typhoons were sampled by two 2DVDs in Guangdong Province (south China). Although the DSD and DSR are different in individual typhoons, the computed DSD parameters in these two groups of typhoons possess similar characteristics. The DSR is more spherical, and the shape-slope (μ-Λ) relation has a significantly lower value of μ for a given Λ than that in typhoons in the Taiwan area, indicating different microphysical processes of typhoons between continental China and other regions (western Pacific and Atlantic). The convective precipitation of typhoons contains higher raindrop concentration and lower raindrop diameter than that of the maritime convection. A Z (reflectivity factor)-R (rain rate) relationship, Z = 147.28R 1.38 , is derived for typhoons over land in China. The contoured frequency by altitude diagrams of CPOL polarimeteric parameters and the vertical distributions of hydrometeors and retrieved DSD parameters are further investigated to better reveal the microphysical processes of two typhoons (Matmo and Soudelor). Despite the differences in DSDs and polarimetric parameters, microphysical characteristics in both typhoons are similar. The CPOL-derived microphysical properties, in conjunction with high freezing level, suggest that warm rain accretion processes dominate typhoon rainfall after landfall in China.In addition to the characteristics of the DSDs, the shapes of the raindrops (axis ratio) also vary a lot with different weather systems because of the oscillation and canting effect of raindrops (e.g., Gorgucci et al., 2000). Polarimetric radars make use of this axis ratio to measure the difference in backscatter reflectivity and the propagation phase (Thurai & Bringi, 2005). Drop shapes therefore play a crucial role in retrieving the DSD of the raindrops and the subsequent estimation of rainfall rates from the polarimetric radar measurements (e.g., Gorgucci et al., 2000). A small error in the axis ratio can lead to significant errors in the estimated DSD and rainfall rates (Bringi & Chandrasekar, 2001).

Microphysical Characteristics of an Asymmetric Eyewall in Major Hurricane Harvey (2017)

“…The characteristic DSD of high concentrations of small raindrops in a TC was consistent with earlier in situ observations from airborne probes (Jorgensen & Willis, 1982) and surface disdrometers (Tokay et al, 2008;Ulbrich & Lee, 2002;Wilson & Pollock, 1974). The DSD variation in TC rainbands (Wang et al, 2016(Wang et al, , 2018Wen et al, 2018) and variability in ice distributions (Didlake & Kumjian, 2017;Kalina et al, 2017) have also been recently investigated. The DSD variation in TC rainbands (Wang et al, 2016(Wang et al, , 2018Wen et al, 2018) and variability in ice distributions (Didlake & Kumjian, 2017;Kalina et al, 2017) have also been recently investigated.…”

“…Brown et al (2016) used radar observations to identify model deficiencies in representing TC DSDs, resulting in improvements to the representation of the snow melting process in the Thompson-Eidhammer microphysical scheme (Brown et al, 2017). The DSD variation in TC rainbands (Wang et al, 2016(Wang et al, , 2018Wen et al, 2018) and variability in ice distributions (Didlake & Kumjian, 2017;Kalina et al, 2017) have also been recently investigated.…”

How Well Can IMERG Products Capture Typhoon Extreme Precipitation Events over Southern China?

“…Secondly, the tremendous wet air masses brought by typhoons interacted with the local mountains in the upward side to produce shallow orographic rainfall. This type of rainfall system tends to be underestimated by PWM algorithm due to weak ice scattering signature [49]. As for IMERG_ERUncal, it shows similar spatial patterns and a little lower precipitation intensities when compared to IMERG_FRCal.…”

Regional Variability of Precipitation in Tropical Cyclones Over the Western North Pacific Revealed by the GPM Dual‐Frequency Precipitation Radar and Microwave Imager

“…To illustrate the near-surface DSD characteristics in different TC regions, the joint distributions of D m and N w at an altitude of 2 km are shown in Figure 5. As illustrated in Wen et al (2018) and Bringi et al (2003), the distributions of D m and N w may reflect the microphysical processes of precipitation. For convective precipitation in the EW region (Figure 5a), the peak frequency occurs mainly when the N w values lie between 40 and 50 and the D m values are between 1.0 and 2.0 mm.…”