Research
I study the tropical cyclones (TCs)， trying to understand the mechanisms involved in TC intensification and size growth.
TC Rapid intensification (RI) is generally defined as an intensification of more than 30 knots in 24 h, most category 4 and 5 hurricanes underwent RI at least once during their lifetimes. TC intensification rate was considered to be tied to local SST warming (e.g., Mei and Xie 2016). However, our recent work suggested that RI favored environments are under the control of global climate variability.
The diurnal cycle is a fundamental characteristic of the variability of the global climate system, various aspects of TCs also fluctuate with the diurnal cycle. Our recent works found that TC intensification, radius of maximum wind (RMW) contraction, and growth of the 34-kt wind radius (R34) were nocturnally prefered. The peak change rates were observed at 0300-0900 LST for rapidly intensifying storms associated with the greatest coverage of very deep convective cloud at 0300–0600 LST. It indicated the importance of radiative forcing on TC structure and intensity. However, we rarely detected diurnal variations in all three phenomena simultaneously in individual storms.
The destructive potential of TCs is primarily determined by two key factors: intensity and the size of the outer region. While the impact of TC wind structure on TC intensification rates has been extensively studied, little has been done to explore its effect on the growth of the outer region. Our recent study found that storms with lower fullness had larger growth rates in the radius of gale-force winds (34 kt or 17 m/s; R34). TC fullness is defined as the ratio of the extent of the outer-core wind skirt to the outer-core size of the TC. This is associated with the higher coverage of very deep convective clouds with infrared brightness temperatures below 208 K around R34 in storms with lower fullness. These findings shed light on the importance of wind structure in the growth of the outer region in TCs, which helps improve our understanding of how these storms change in outer-core size.
