Season-Dependent Distributions and Profiles of Seven Super-Typhoons (2014) in the Northwestern Pacific Ocean From Satellite Cloud Images

This paper extends a former study on supertyphoon's formation in winter to its seasonal dependence on distribution and profiles. It aims to enhance understanding and predictability of the super-typhoons to reduce their impacts on human beings and properties in the regions where they pass by or influence. A framework by integrating remote-sensing imagery and image-processing techniques is implemented to analyze the seven super-typhoons of concern in both summer and winter seasons in the northwestern Pacific Ocean. Conventionally, typhoons occur in summer in the Northern Hemisphere, while owing to increased climate variability in recent decades, the occurrence of typhoons in winter is increased and a large number of super-typhoons are observed. Surprisingly, three summer super-typhoons-Neoguri (July), Rammasun (July), and Halong (August)-and four winter super-typhoons-Phanfone (October), Vongfong (October), Nuri (November), and Hagupit (December)-happened in 2014. Their physical responses of tracks, distributions, profiles, and intensifications are examined. The 3-D profiles of typhoons derived from surface cloud images are used to investigate the in-depth distributions of the cloud tops. Results show that southwest airflows, and cold fronts and southwest airflows enhance the summer and winter typhoons, respectively, to become super-typhoons eventually within the zones of lat 15°-20° and 10°-20°N and long 110°-135° and 133°-138°E in summer and winter, respectively. The lat 20°N is likely the boundary for the super-typhoons' occurrence and a turning point of the typhoons' two major tracks, with the first track moving in the westerly direction and the second track inclining in the northerly direction. Three crucial findings are obtained. First of all, it is observed that Track 1 inclined toward the latitude with an inclination angle θ
₁
and Track 2 inclined toward Track 1 with an inclination angle θ
₂
. Using both inclination angles, the patterns of the super-typhoons were approximately described. Second, the inclination angle θ1 of the winter super-typhoons is represented with smaller values and a narrower range (10°-26°) than those (13°-40°) of the summer super-typhoons. After the turning point, both inclination angles θ
₂
of winter and summer super-typhoons varied with a wider range of 25°-65° and -35° to 50°, respectively. The winter super-typhoons exhibit higher intensities than the summer super-typhoons. Third, it is further confirmed that a mechanism through which cold fronts and southwest airflows enhance the typhoons causes them to become super-typhoons. The cold front is a new aspect of the leading edge of cooler air masses in typhoon environments exerting a greater temperature gradient between the front and typhoon circulation that ultimately affects the track of typhoons and increases the intensity of typhoons.