资源环境科技发展态势分析平台

This study analyzed the temporal/spatial distribution of the high-temperature extremes (HTEs) in Taiwan. Three major weather types for HTEs were identified: the southerly/southwesterly (S/SW) (47.6%), western North Pacific subtropical high (SH) (35.9%), and tropical cyclone (16.5%). The S/SW type features anomalous warm advection in lower atmosphere and anomalous subsidence in all the altitudes around Taiwan. Different from the S/SW type, the SH type warms the surface primarily with increasing downward shortwave radiation. In June, the S/SW type was the most common. In July, both the S/SW and SH types dominated. In August, the tropical cyclone and SH types were more common. The subseasonal variation of extreme hot days (EHDs) for these three weather types is examined. Taipei and Dawu were two HTE hot spots in Taiwan. EHDs in Taipei occurred mostly in July and August, with the SH being the major type. Most EHDs in Dawu occurred in June, with the S/SW being the predominant type. These differences likely resulted from not only the subseasonal monsoon variation but also geographical differences. The interannual variability of the summer EHDs in Taiwan was found to be related to the phase and intensity of the El Nino-southern oscillation events. The number of EHDs increased in the El Nino decaying summers and decreased in the La Nina decaying summers. The correlation between the number of summer EHDs and the Nino 3.4 SST anomaly reaches its peak in the previous winter (November/December). The associated mechanisms were discussed in the article.