An Abrupt Decrease in the Late-Season Typhoon Activity over the Western North Pacific*

• DOI: 10.1175/jcli-d-13-00417.1
• Publication Date: 2014-03-10T19:15:23Z
• Authors: Pang-Chi Hsu; Pao-Shin Chu; Hiroyuki Murakami; Xin Zhao
• Keywords: Typhoon; Anomaly (physics)

Abstract In 1995 an abrupt shift in the late-season (October–December) typhoon activity over western North Pacific (WNP) is detected by a Bayesian changepoint analysis. Interestingly, similar change also occurs sea surface temperature series Pacific, eastern and portions of Indian Ocean. All counts, lifespans, accumulated cyclone energy typhoons during 1995–2011 epoch decreased significantly, compared with that occurred 1979–94 epoch. The negative vorticity anomaly found to be leading contributor genesis potential index (GPI) decrease southeastern sector WNP 1995–2011. To elucidate origin epochal dynamic environmental conditions, suite sensitivity experiments conducted based on latest version Japan Meteorological Research Institute atmospheric general circulation model (MRI AGCM). ensemble simulations suggest recent La Niña–like state induces unfavorable condition for WNP. Warming Ocean, however, contributes insignificantly related frequency occurrence reveals basinwide epoch, except small increase near Taiwan. An empirical statistical analysis shows primarily attributed genesis, while track less importance.