Atmos. Chem. Phys. Discuss., 10, 16589-16635, 2010
© Author(s) 2010. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
The vorticity budget of developing Typhoon Nuri (2008)
D. J. Raymond and C. López Carrillo
Physics Department and Geophysical Research Center, New Mexico Tech, Socorro, NM, USA

Abstract. The formation of west Pacific tropical cyclone Nuri (2008) was observed over four days from easterly wave to typhoon stage by aircraft using scanning Doppler radar and dropsonde data. This typhoon intensified rapidly in a significantly sheared environment. In spite of the shear, overlapping closed circulations existed in the storm frame of reference in the boundary layer and at 5 km elevation, providing a deep region protected from environmental influences. The vorticity budget was analyzed and it was found that vorticity convergence dominated vortex tilting on the storm scale in the lower troposphere. At times vorticity convergence also greatly exceeded frictional spindown in the boundary layer. Thus, the Ekman pumping hypothesis was found to be a poor approximation in the early stages of the development of this typhoon. As Nuri developed, convective sources of boundary layer vorticity became fewer but more intense, culminating in a single nascent eyewall at the tropical storm stage. A non-developing tropical wave case was also analyzed. This system started with much weaker circulations in the boundary layer and aloft, leaving it unprotected against environmental intrusion. This may explain its failure to develop.

Citation: Raymond, D. J. and López Carrillo, C.: The vorticity budget of developing Typhoon Nuri (2008), Atmos. Chem. Phys. Discuss., 10, 16589-16635, doi:10.5194/acpd-10-16589-2010, 2010.
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