Tropical cyclone climatology and variability in Taiwan and Philippine Region during 1979 - 2018

  • Taiwan-Philippine area experienced an unusually low TC activity period (1997-2002)
  • Low TC activity south to 16°N was due to Philippine Sea anticyclone anomaly (PSA)
  • The PSA was associated with strong Asian summer monsoon and SCS autumn convection

Taiwan and Philippine (TWPH) (117 - 129°E, 5 - 26°N) is a region with most frequent and intense tropical cyclone (TC) influence in the world. This paper documents the climatology and variability of TWPH TC activity with specific attention to the difference in the TCs formed over the western North Pacific (WNP) and over the South China Sea (SCS). The spatial characteristics of TWPH TCs are analyzed based on the accumulated cyclone kinetic energy (ACE) in four sub-areas where distinctly different TC seasonality and variability is found. Different from over the broad Northwest Pacific Basin (0 - 60°N, 100°E - 180°) where the WNP-born TC frequency dropped sharply in late-1990s and the SCS-born TC frequency slightly increased in mid-1990s, over TWPH three distinct epochs are identified. A weakvariability epoch occurred during 1979 - 1996, a persistent low-ACE epoch during 1997 - 2002, and a more variable epoch during 2003 - 2018. The second epoch is most noteworthy. The unusually weak TC activity during this period in particular over the Philippines was associated with anomalously strong anticyclone over the SCS and the Philippine Sea during the East Asian summer monsoon season. The strong anticyclonic circulation appeared as a descending leg of the enhanced East Asian summer monsoon during summer (July to September). During autumn and early winter (September to December) the Philippine Sea anticyclone was interpreted as the descending Rossby wave response to the suppressed convection over tropical western Pacific. The anomalous anticyclone strengthened the low-level confluent flow and convection over the SCS. The findings are useful to real-time TWPH TC activity monitoring and analysis.

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