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Intensity change of binary Tropical Cyclones (TCs) in idealized numerical simulations: two initially identical mature TCs

Liu, H.-Y., Wang, Y. and Gu, J.-F. ORCID: https://orcid.org/0000-0002-7752-4553 (2021) Intensity change of binary Tropical Cyclones (TCs) in idealized numerical simulations: two initially identical mature TCs. Journal of the Atmospheric Sciences, 78 (4). pp. 1001-1020. ISSN 1520-0469

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To link to this item DOI: 10.1175/JAS-D-20-0116.1

Abstract/Summary

This study investigates the intensity change of binary tropical cyclones (TCs) in idealized cloud-resolving simulations. Four simulations of binary interaction between two initially identical mature TCs of about 70 ms−1 with initial separation distance varying from 480 to 840 km are conducted in a quiescent f-plane environment. Results show that two identical TCs finally merge if their initial separation distance is within 600 km. The binary TCs presents two weakening stages (stages 1 and 3) with a quasi-steady evolution (stage 2) in between. Such intensity change of one TC is correlated with the upper-layer vertical wind shear (VWS) associated with the upper-level anticyclone (ULA) of the other TC. The potential temperature budget shows that eddy radial advection of potential temperature induced by large upper-layer VWS contributes to the weakening of the upper-level warm core and thereby the weakening of binary TCs in stage 1. In stage 2, the upper-layer VWS first weakens and then re-strengthens with relatively weak magnitude, leading to a quasi-steady intensity evolution. In stage 3, due to the increasing upper-layer VWS, the non-merging binary TCs weaken again until their separation distance exceeds the local Rossby radius of deformation of the ULA (about 1600 km), which can serve as a dynamical critical distance within which direct interaction can occur between two TCs. In the merging cases, the binary TCs weaken prior to merging because highly asymmetric structure develops as a result of strong horizontal deformation of the inner core. However, the merged system intensifies shortly after merging.

Item Type:Article
Refereed:Yes
Divisions:Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:95628
Publisher:American Meteorological Society

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