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The abnormal weather and climate patterns over Taiwan during the 1998 El Nino

Jau-Ming Chen¹, Fong-Ju Weng

Central Weather Bureau

In Taiwan, the annual-mean climate of the 1998 El Nino year is warmest and wettest since 1970. Some noticeable abnormal weather and climate patterns in Taiwan for the 1998 El Nino year are summarized as follows.

(1) For the entire year, each of the 12 monthly-mean temperatures of 1998 is warmer than the corresponding temperature climatology. Annual evolution of the above-normal temperature anomalies is rather consistent with the evolution of warm SST anomalies over the South China Sea and the western Pacific between Taiwan and Japan.

(2) For the spring season (February-April), the total precipitation amount over Taiwan is above normal when compared with climatology. Increase in precipitation amount is accompanied with the weakening of the local Hadley circulation around Taiwan area and the tropical Walker circulation over the equatorial Pacific. Changes in Hadley circulation and Walker circulation are in connection with the existence of significant warm SST anomalies in the eastern tropical Pacific.

(3) For the Mei-Yu season (May-June), the precipitation amount in Taiwan is also above normal when compared with climatology. Moreover, the precipitation evolution during this season shows a clear intraseasonal variation that is highly correlated with the intraseasonal variation of convection activities over the South China Sea.

(4) For the typhoon season (July-October), the precipitation in both July and August is below normal because only one weak typhoon passed Taiwan area in each month. In September, one typhoon (Typhoon Yanni) passed Taiwan area which brought in significant rainfall and made precipitation amount in this month about normal. In October, two typhoons (Typhoons Zeb and Babs) passed Taiwan area to result in above normal precipitation amount in this month.

¹E-mail: cjming@bingo.cwb.gov.tw

Labels: weather