Genesis and development processes of a quasi-stationary carrot-shaped cloud system around the Sakishima Islands in Japan
Abstract
A number of carrot-shaped cloud systems (CSCSs) occur around the Sakishima Islands in Japan. They often stagnate for a few hours and produce heavy rainfall. Therefore, it is very important to clarify the genesis, development and stagnation processes of CSCSs around the Sakishima Islands. We focus on two factors. One is the Taiwan topography, and the other is the Kuroshio Current. The Sakishima Islands are located east of the Taiwan Island. Therefore, when low-level winds are westerlies or southwesterlies, low-level winds around the Sakishima Islands are strongly influenced by the Taiwan topography. In addition, the warm Kuroshio Current supplies heat and water vapor to the low-level troposphere. A numerical simulation with realistic conditions well reproduces a CSCS that occurred in the vicinity of the Sakishima Islands on 17 March 2013. Low-level winds modulated by the Taiwan topography forms the convergence zone in the lee (east) side of the island, which leads to the occurrence of a line-shaped convective system. The convergence zone is stagnated by the orographic effect throughout the mature stage of the system. Consequently, the quasi-stationary CSCS is maintained for a few hours. In a simulation with the flatten Taiwan topography, a CSCS occurs but moves eastward, which suggests that the Taiwan topography plays an important role in stagnating the convective system. In contrast, a simulation in which a part of the Kuroshio Current is cooled does not produce convection in the lee side of the Taiwan Island. Lower equivalent potential temperature and weaker surface winds on the cooled Kuroshio Current are responsible for no convection.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.A41C0053K
- Keywords:
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- 3310 Clouds and cloud feedbacks;
- ATMOSPHERIC PROCESSESDE: 3314 Convective processes;
- ATMOSPHERIC PROCESSES