3:30 PM - 3:45 PM
[AAS02-12] Evaluation of the monthly Potential of the 2018 typhoon activity and the effect of the positive PMM and SST of the eastern northwestern Pacific
Keywords:tropical cyclone, Pacific Meridional Mode, nonhydrostatic model
The purpose of this research is to focus on the monthly SST variation such as ENSO and PMM and to evaluate the Potential of the 2018 typhoon activity. We also focus on the PMM and the SST over the eastern of northwest Pacific, and investigate how they affect the 2018 typhoon activity.
For the above purpose, we conducted perpetual experiments in which boundary conditions were fixed from July to October, respectively, using a nonhydrostatic model NICAM. The horizontal resolution was 56 km, and the number of vertical layers was 38 layers. In sensitivity experiments, PMM region and PMM + eastern northwest Pacific regions of SST in July 2018 sensitivity experiment 1 and sensitivity experiment 2 replaced with climate value were conducted. Comparing the experimental result of sea level pressure (hereafter SLP) with JRA-55, although the position of the maximum value of the high pressure in July is misaligned, the position and overhang of the high pressure does not differ greatly in each month, and perpetual experiments also reproduce the reality well. Both reanalysis and perpetual experiments have more typhoons in July and August than in September and October. Also, the occurrence position of the typhoon occurs more frequently in the eastern side of the northwestern Pacific in order of July, August, September. The same tendency was observed. Such differences in active areas of typhoon activity had an effect on the monsoon trough.
Subsequently, the SLPs of the 2018 experiment, sensitivity experiment 1 and sensitivity experiment 2 were compared. In comparison with the sensitivity experiment 1, the sensitivity experiment 1 became a lower pressure deviation in the west side of the northwest Pacific than 2018 experiment, whereas in the sensitivity experiment 2, the sensitivity experiment 2 had higher SLP in the whole northwest Pacific than 2018 experiment. From this, it was found that the positive SST deviation in the eastern northwest Pacific was more involved in the typhoon activity of 2018.