A Positive Feedback Process Between Tropical Cyclone Intensity and the Moisture Conveyor Belt Assessed With Lagrangian Diagnostics

• Published in: Journal of geophysical research. Atmospheres 2017-12, Vol.122 (23), p.12,502-12,521
• Main Authors: Fujiwara, Keita, Kawamura, Ryuichi, Hirata, Hidetaka, Kawano, Tetsuya, Kato, Masaya, Shinoda, Taro
• Format: Article
• Language: English
• Subjects: Air parcels; Atmospheric boundary layer; Belt conveyors; Boundary layers; Cyclones; Equatorial waves; Feedback; Geophysics; Heating; Hurricanes; Inflow; Lagrangian diagnostics; Latent heat; Moisture; moisture transport; Monsoons; Oceans; Positive feedback; Regional analysis; Sea surface; Sea surface temperature; Surface temperature; Temperature distribution; Temperature fields; Tropical climate; tropical cyclone; Tropical cyclones; Vapors; Water inflow; Wave propagation; Westerlies
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2017JD027557

Using a cloud‐resolving regional model and Lagrangian diagnostics, we assess a positive feedback process between tropical cyclone (TC) intensity and the moisture conveyor belt (MCB), which connects a TC and the Indian Ocean (IO), the South China Sea (SCS), and the Philippine Sea (PS) vapors, from a macroscopic view. We performed sensitivity experiments that modified the observed sea surface temperature field over the IO and the SCS to regulate the MCB behavior, and we examined the remote response of a prototypical TC. The results show that the connection between MCB formation and TC development is very robust, which was also observed in another TC's case. The MCB plays a vital role in transporting lots of moist air parcels toward the TC from the IO, SCS, and PS regions. The transported parcels, which further gained the underlying ocean vapor along the MCB, are easily trapped in the inner core by radial inflow in the atmospheric boundary layer and, subsequently, release latent heat around the eyewall, resulting in the TC's intensifying. This acts to further penetrate the moist parcels of remote ocean origin into the inner core through the enhanced and expanded inflow. An additional experiment suggested that the MCB is not formed unless the westward propagation of equatorial waves induced by TC heating overlaps with the background monsoon westerlies. These findings support the reliability and validity of TC–MCB feedback. Key Points The intensity of a tropical cyclone is influenced by moisture of remote ocean origin The moisture conveyor belt transports moist air parcels toward the tropical cyclone The presence of a tropical cyclone is indispensable to the moisture conveyor belt formation