Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

A (Atmospheric and Hydrospheric Sciences) » A-CG Complex & General

[A-CG44] Promotion of Application and Utilization of Aircrafts for Earth sciences

Tue. May 22, 2018 3:30 PM - 5:00 PM A08 (Tokyo Bay Makuhari Hall)

convener:Nobuhiro Takahashi(Institute for Space-Earth Environmental Research, Nagoya University), Makoto Koike(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Toshinobu Machida(国立環境研究所, 共同), Taro Shinoda(Institute for Space-Earth Environmental Research, Nagoya University), Chairperson:Takahashi Nobuhiro(Institute for Space-Earth Environmental Research, Nagoya University)

4:00 PM - 4:15 PM

[ACG44-03] Observing System Experiment using T-PARCII dropsondes and JMA Global Forecasting System and Development of Sensitivity Analysis Guidance for Tropical Cyclone Intensity

*Munehiko Yamaguchi1, Toshiyuki Ishibashi1, Tetsuo Nakazawa1, Kosuke Ito2, Hiroyuki Yamada2, Tadayasu Ohigashi3, Taro Shinoda4, Nobuhiro Takahashi4, Kazuhisa Tsuboki4 (1.Meteorological Research Institute, Japan Meteorological Agency, 2.Faculty of Science, University of the Ryukyus, 3.Disaster Prevention Research Institute, Kyoto University, 4.Institute for Space-Earth Environmental Research, Nagoya University)

Keywords:Tropical Cyclone, Aircraft, Observation, Observing System Experiment, Sensitivity Analysis

Airborne typhoon observations were conducted for Typhoon Lan (2017) under Tropical cyclones-Pacific Asian Research Campaign for Improvement of Intensity estimations/forecasts (T-PARCII). Twenty one dropsonde data including six in the eye of Typhoon Lan were obtained during 05-07 UTC of 21 October 2017. Using the dropsonde data (zonal and meridional winds, temperature, and relative humidity) and the Japan Meteorological Agency Global Spectral Model (JMA/GSM, TL959L100) and 4 Dimensional Variational data assimilation (4DVAR, TL319L100), we performed Observing System Experiment (OSE) to see the impact of the newly available observational date on the track/intensity forecasts by the JMA/GSM. The observation errors for the dropsondes were the same as those used in the operational 4DVAR (same values used for radiosonde and dropsonde). Different from the operational 4DVAR, which includes Quality Control (QC) of assimilated observations, the dropsonde data were forcibly assimilated no matter how large the departures (observation – background) were.

The result of the OSE initiated at 06 UTC of 21 October 2017 showed that the impact of assimilating the dropsondes was little. This would be due to the fact that the track/intensity forecasts of Typhoon Lan by JMA/GSM at this initial time had small errors even without the dropsondes and that there were little room for improvement. In addition, the outer/inner models with a horizontal resolution of 20/60 km, respectively, may have been too coarse as the dropsondes were deployed in and around the TC core.

We developed sensitivity analysis technique for TC intensity using the adjoint model of the 4DVAR. According to the sensitivity analysis guidance targeted at 06 UTC of 21 October 2017, the secondary circulation, especially in the west side of the TC, is found to be sensitive to the future change of the TC intensity. For example, the outflow area at around 200 hPa and 100 – 500 km away from the TC center had large sensitivity. As no observation was available in the sensitivity area, unfortunately the impact of the sensitivity analysis guidance could not be evaluated. This will be a future study.