Large-scale processes modulating the frequency of typhoons affecting Taiwan during 1900-1945

10.3319/TAO.2021.11.29.01

Pei-Hua Tan；Jien-Yi Tu；Mei-Yun Tsai

Interannual variability ； Typhoon track ； Cold period ； Presatellite era ； Intraseasonal oscillation

Terrestrial, Atmospheric and Oceanic Sciences

32卷6III期（2021 / 12 / 01）

1197 - 1213

英文

The typhoons affecting Taiwan during 1900-1945 are defined as those with a low-pressure center making a landfall in Taiwan or moving near Taiwan and included in disaster reports. The annual and monthly numbers of typhoons were lower during 1900-1945 than during 1970-2015, which might be attributed to the colder environment, a weakened western North Pacific subtropical high with the eastward retreat and lack of satellite detection techniques during 1900-1945. However, the monthly percentages of typhoons were comparable in the high-frequency months of July-September during the two periods. In contrast to the warm period, the cold period had fewer total typhoon numbers but more concentrated occurrence during May-October. During 1900-1945, an interannual variability of the typhoon frequency affecting Taiwan was observed. During the typhoon-more (typhoon-less) years, the significant sea surface temperature patterns were dominated by warm (cold) anomalies elongating the tropical central-eastern Pacific with a maximum center in the central Pacific and cold (warm) anomalies over the tropical western Pacific. The anticyclonic (cyclonic) circulation around Taiwan that responds to a divergent (convergent) center in the Maritime Continents tended to provide a favorable (unfavorable) steering flow to force typhoons over the east of the Philippines moving westward/northwestward (eastward) toward (away from) Taiwan. The modulations of intraseasonal oscillations on typhoon movements under the westward/northwestward and northward tracks of typhoons affecting Taiwan exerted a positive but different effect on steering the typhoon toward or near Taiwan.