A numerical model study about the impacts of dry air on tropical cyclone formation

Fritz, Cody

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https://hdl.handle.net/2142/29479 Copy

Description

Title

A numerical model study about the impacts of dry air on tropical cyclone formation

Author(s)

Fritz, Cody

Issue Date

2012-02-01T00:48:29Z

Director of Research (if dissertation) or Advisor (if thesis)

Wang, Zhuo

Department of Study

Atmospheric Sciences

Discipline

Atmospheric Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• tropical cyclone
• dry air impacts
• pre-genesis

Abstract

The impacts of dry air on tropical cyclone formation are examined in the numerical model simulations of ex-Gaston (2010) and pre-Fay (2008). The former can be regarded as a non-developing system as it failed to redevelop after being downgraded into a remnant low, and the latter developed into a tropical cyclone despite lateral dry air entrainment and transient upper-level dry air intrusion. Backward trajectory analysis and water budget analysis show that vertical transport of dry air from the upper troposphere, where a well-defined wave pouch is absent, contributes to mid-level drying near the pouch center and the non-development of ex-Gaston. Water vapor budget analysis at the pre-genesis stage shows that vertical moisture advection plays the dominant role in moistening the free atmosphere. Persistent mid-level drying is shown to suppress deep convection and reduce moisture supply to the free atmosphere. Three-dimensional trajectory analysis based on the numerical simulation of Fay suggests that dry air entrained at the pouch periphery does not penetrate to the pouch center due to the weak mid-level inflow. Moreover, it is shown that dry air gets moistened as it is being wrapped into the wave pouch, and lateral entrainment in the middle troposphere thus does not suppress convection near the pouch center or prevent development of tropical storm Fay.

Graduation Semester

2011-12

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http://hdl.handle.net/2142/29479

Copyright and License Information

Copyright 2011 Cody L. Fritz

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