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Tsuji, H., and Y. N. Takayabu, 2023: A hierarchical structure of the heavy rainfall event over Kyushu in July 2020. J. Meteor. Soc. Japan, 101.
https://doi.org/10.2151/jmsj.2023-017
Special Edition on Research on Extreme Weather Events that occurred around East Asia in 2017-2021
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Plain Language Summary: The heavy rainfall event in July 2020 over Kyushu Island, Japan is analyzed focusing on a hierarchical structure. Before the rainfall event, an upper tropospheric trough, a mesoscale depression, and a sub-synoptic scale cloud system prepare an environment favorable for organized precipitation systems bringing a large precipitation amount. At the rainfall event, a mesoscale convective system with moist absolutely unstable layers (MAULs) develops in Kyushu, causing the disastrous rainfall event. These results suggest that the rainfall event is characterized by a hierarchical structure such that the organized precipitation system causing the rainfall event develops under the environment generated by the upper-tropospheric trough, the sub-synoptic scale cloud system, and the mesoscale depression.

Highlights:

• A hierarchical structure associated with the heavy rainfall event in July 2020 over Kyushu is analyzed.
• An upper tropospheric trough, a mesoscale depression, and a sub-synoptic scale cloud system contribute to moistening the atmosphere and increasing baroclinicity around Kyushu before the rainfall event.
• An organized precipitation system with MAUL develops in the prepared environment, causing the rainfall event.