JpGU-AGU Joint Meeting 2017

Presentation information

[EE] Poster

A (Atmospheric and Hydrospheric Sciences) » A-AS Atmospheric Sciences, Meteorology & Atmospheric Environment

[A-AS06] [EE] Advances in Tropical Cyclone Research: Past, Present, and Future

Sat. May 20, 2017 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL7)

[AAS06-P12] Unusual growth in intense typhoon occurrences over the Philippine Sea in September after the mid-2000s

*Jing Yang1 (1.Beijing Normal University)

Keywords:tropical cyclone, decadal change

During the global warming hiatus period (1998–

present), a pronounced increase in the number of intense

typhoon occurrences was identified over the Philippine

Sea (PS: 5°–25°N, 125°–140°E) in September after the

mid-2000s. Comparing two periods before and after the

mid-2000s indicates that intense typhoons rarely occurred

over the PS in September before the mid-2000s, with a frequency

of fewer than 0.4 per year, but reached up to nearly

1.5 per year after the mid-2000s. The abrupt increase in

intense typhoon occurrences over the PS was primarily

attributed to increased tropical cyclone (TC) genesis and

favorable large-scale conditions for TC intensification. The

increase in TC genesis number over the PS was caused

by contributory dynamical conditions, including positive

low-level relative vorticity anomalies and anomalous

ascents, which corresponded to a southwestward shift and

strengthening of the monsoon trough. In addition, among

the favorable large-scale conditions, the increased relative

humidity that resulted from intensified moisture flux

convergence exerted essential effect on the TC intensification.

These changes in atmospheric environmental conditions

favoring intense typhoon occurrences over the PS

were primarily associated with the change in the tropical

Indo-Pacific sea surface temperature (SST) around the mid-

2000s. Besides that, the positive feedback TCs exerted on

the circulation was also conducive to the unusual growth in

intense typhoon occurrences over the PS. And note that the

role of SST anomalies in the air–sea interaction is the key

to interpret why the unique phenomenon only occurred in