The formation mechanism of the Bonin high in August

The Bonin high is a subtropical anticyclone that is predominant near Japan in the summer. This anticyclone is associated with an equivalent‐barotropic structure, often extending throughout the entire troposphere. Although the equivalent‐barotropic structure of the Bonin high has been known for years...

Full description

Saved in:
Bibliographic Details
Published in:Quarterly journal of the Royal Meteorological Society 2003-01, Vol.129 (587), p.157-178
Main Authors: Enomoto, Takeshi, Hoskins, Brian J., Matsuda, Yoshihisa
Format: Article
Language:English
Subjects:
Asian jet
Desert descent
Earth, ocean, space
Exact sciences and technology
External geophysics
Indian summer monsoon
Meteorology
Rossby waves
Silk Road
Weather analysis and prediction
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The Bonin high is a subtropical anticyclone that is predominant near Japan in the summer. This anticyclone is associated with an equivalent‐barotropic structure, often extending throughout the entire troposphere. Although the equivalent‐barotropic structure of the Bonin high has been known for years among synopticians because of its importance to the summer climate in east Asia, there are few dynamical explanations for such a structure. The present paper attempts to provide a formation mechanism for the deep ridge near Japan. We propose a new hypothesis that this equivalent‐barotropic ridge near Japan is formed as a result of the propagation of stationary Rossby waves along the Asian jet in the upper troposphere (‘the Silk Road pattern’). First, the monthly mean climatology is examined in order to demonstrate this hypothesis. It is shown that the enhanced Asian jet in August is favourable for the propagation of stationary Rossby waves and that the regions of descent over the eastern Mediterranean Sea and the Aral Sea act as two major wave sources. Second, a primitive‐equation model is used to simulate the climatology of August. The model successfully simulates the Bonin high with an equivalent‐barotropic structure. The upper‐tropospheric ridge is found to be enhanced by a height anomaly of more than 80 m at 200 hPa, when a wave packet arrives. Sensitivity experiments are conducted to show that the removal of the diabatic cooling over the Asian jet suppresses the Silk Road pattern and formation of an equivalent‐barotropic ridge near Japan, while the removal of the diabatic heating in the western Pacific does not. Copyright © 2003 Royal Meteorological Society
ISSN:0035-9009
1477-870X
DOI:10.1256/qj.01.211