Yamada, H., K. Ito, K. Tsuboki, T. Shinoda, T. Ohigashi, M. Yamaguchi, T. Nakazawa, N. Nagahama, and K. Shimizu, 2021: The double warm-core structure of Typhoon Lan (2017) as observed through the first Japanese eyewall-penetrating aircraft reconnaissance. J. Meteor. Soc. Japan, 99,
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Eyewall-penetrating upper-tropospheric aircraft reconnaissance was carried out for Typhoon Lan (2017). This was the first case of a Japanese research group observing the inner core of an intense typhoon using dropsondes. We captured a double warm-core structure persisted in an environment with a strengthening vertical wind shear. Based on analyses of thermodynamics, we hypothesize the contribution of a high enthalpy air transported from the eye boundary layer into the upper warm core via the eyewall for the continuous eye warming.
- The two warm cores show a difference in the equivalent potential temperature (θe) of more than 10 K, suggesting different air origins.
- The thermodynamic pathway of high-θe air into the upper warm core from the eye boundary layer was characterized by temperatures almost fitted to a single moist adiabatic line.
- This study demonstrates the significance of eye-penetrating upper-tropospheric reconnaissance for understanding thermodynamic processes related to typhoon intensity.