Tropical cyclones-Pacific Asian Research Campaign for Improvement of Intensity estimations/forecasts (T-PARCII): A Summary of the Ten-Year Project and Future PerspectivesKazuhisa TsubokiInstitute for Space-Earth Environmental Research (ISEE), Nagoya University /Typhoon Science and Technology Research Center (TRC), Yokohama National University, Japan |
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The T-PARCII (Tropical cyclone-Pacific Asian Research Campaign for Improvement of Intensity estimations/forecasts) project has been conducted for 2016-2021 as the first phase and 2021-2026 as the second phase. The objectives of T-PARCII are improvements of intensity estimations and predictions of the tropical cyclones (TCs) in the western North Pacific. In this project, dropsonde observations of supertyphoons were performed using jet aircrafts Gulfstream II (G-II) in the first phase and Gulfstream IV (G-IV) in the second phase. By the end of October 2025, T-PARCII made successfully dropsonde observations of typhoon Lan in October 2017, Trami in September 2018, Mindulle in September 2021, Nanmadol in September 2022, an atmospheric river associated with typhoon Aere in July 2022, Barijat in October 2024, Neoguri in September 2025, and Halong in October 2025. The dropsonde used in the T-PARCII project was newly developed by Nagoya University and Meisei Electric CO., LTD. The body of dropsonde is made of biodegradable materials. In each flight, 20~30 dropsondes were launched from a height of 45,000 ft in the inner core region and inside eyes of typhoons. Dropsonde data were transmitted to the Japan Meteorological Agency from the aircraft in real time and then sent to GTS for operational forecasts. In the observation of Supertyphoon Lan, a dynamic and thermodynamic structure of inner core region were observed by dropsondes. The warm core had two peaks at upper and lower levels, which may be a characteristic of supertyphoon (Yamada et al. 2021). The formation process of the warm core peaks was studied using numerical model (Tsujino et al. 2022). The dropsonde data were assimilated to a numerical model to improve typhoon forecast (Ito et al. 2018). The aircraft observations of Trami were performed in collaboration with the Hokkaido University project and four-day observations were made. Trami showed a rapid weakening of intensity in two days. This may be related to incomplete replacement of concentric eyewalls. As a result, a characteristic cloud named "deep eye clouds" formed inside the eye (Hirano et al. 2022). The dropsonde observations provided accurate data of central sea level pressure of typhoons Lan and Trami, which showed a large error of intensity estimations using Dvorak method. In the second phase of T-PARCII, we addressed dropsonde observations of rapid intensification and concentric eyewall structure of supertyphoon Nanmadol. Satellite observations and radar of G-IV showed concentric eyewalls of Nanmadol with the small eye of 20 km diameter. The two-day observations showed a rapid increase in wind speed more than 15 m/s within 20 h in the deep layer up to 300 hPa. This is a rapid intensification with the wind speed increase in the deep layer. An assimilation of dropsonde data observed at the center of the eye significantly improved the simulation of thermodynamic structure of the warm core and intensity forecasts. |