Baroclinic developments in jet entrances and exits. I: Linear normal modes

✍ Scribed by Sylvia H. E. Hare; I. N. James

• Book ID: 104576508
• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 1017 KB
• Volume: 127
• Category: Article
• ISSN: 0035-9009
• DOI: 10.1002/qj.49712757409

✦ Synopsis

Abstract

This study examines the effect of the ageostrophic circulations associated with jet entrance and exit regions on the structure and growth rates of baroclinic normal modes. A linearized GCM is used to find the most unstable normal‐mode disturbances for a zonally symmetric basic state consisting of a zonal jet and meridional circulation. Normal‐mode growth rates are reduced by up to 20% for realistic strengths of meridional overturning, and normal‐mode structures are significantly affected. For example, the normal‐mode poleward tilt with height varies, affecting the conversion of basic‐state available energy. A mechanism for the change in poleward tilt is proposed. Ageostrophic meridional circulations may play a significant role in determining the magnitude and length of mid‐latitude storm tracks.