Book contents
- Frontmatter
- Contents
- Contributors
- Editors' preface
- Keynote address to the 1977 Symposium SIR JAMES LIGHTHILL
- Part I The large-scale climatology of the tropical atmosphere
- Part II The summer monsoon over the Indian subcontinent and East Africa
- 12 The monsoon as reflected in the behaviour of the tropical high-pressure belt
- 13 On the onset of the Indian southwest monsoon and the monsoon general circulation
- 14 Medium-range forecasting of monsoon rains
- 15 Sea-surface temperature and the monsoon
- 16 The effect of elevation on monsoon rainfall distribution in the central Himalayas
- 17 Use of the equation of continuity of water vapour for computation of average precipitation over peninsular India during the summer monsoon
- 18 Determination of cloud cluster properties from MONSOON-77 data
- 19 Analysis of superpressure balloon trajectories and conventional observations over the Indian Ocean during different phases of the 1975 southwest monsoon
- 20 An experiment in monitoring cross-equatorial airflow at low level over Kenya and rainfall of western India during the northern summers
- 21 Structure of the Somali Jet deduced from aerial observations taken during June–July, 1977
- 22 Certain aspects of monsoonal precipitation dynamics over Lake Victoria
- 23 A numerical model of the monsoon trough
- 24 On the monsoonal midtropospheric cyclogenesis over western India
- 25 Downstream development of baroclinic waves in the uppertropospheric monsoon easterlies suggested by a simple model experiment
- 26 The stability of the monsoon zonal flow with a superposed stationary monsoon wave
- 27 Growth of monsoon disturbances over western India
- 28 Topographic Rossby waves in the summer monsoon
- Part III The physics and dynamics of the Indian Ocean during the summer monsoon
- Part IV Some important mathematical modelling techniques
- Part V Storm surges and flood forecasting
- Index
27 - Growth of monsoon disturbances over western India
Published online by Cambridge University Press: 05 November 2011
- Frontmatter
- Contents
- Contributors
- Editors' preface
- Keynote address to the 1977 Symposium SIR JAMES LIGHTHILL
- Part I The large-scale climatology of the tropical atmosphere
- Part II The summer monsoon over the Indian subcontinent and East Africa
- 12 The monsoon as reflected in the behaviour of the tropical high-pressure belt
- 13 On the onset of the Indian southwest monsoon and the monsoon general circulation
- 14 Medium-range forecasting of monsoon rains
- 15 Sea-surface temperature and the monsoon
- 16 The effect of elevation on monsoon rainfall distribution in the central Himalayas
- 17 Use of the equation of continuity of water vapour for computation of average precipitation over peninsular India during the summer monsoon
- 18 Determination of cloud cluster properties from MONSOON-77 data
- 19 Analysis of superpressure balloon trajectories and conventional observations over the Indian Ocean during different phases of the 1975 southwest monsoon
- 20 An experiment in monitoring cross-equatorial airflow at low level over Kenya and rainfall of western India during the northern summers
- 21 Structure of the Somali Jet deduced from aerial observations taken during June–July, 1977
- 22 Certain aspects of monsoonal precipitation dynamics over Lake Victoria
- 23 A numerical model of the monsoon trough
- 24 On the monsoonal midtropospheric cyclogenesis over western India
- 25 Downstream development of baroclinic waves in the uppertropospheric monsoon easterlies suggested by a simple model experiment
- 26 The stability of the monsoon zonal flow with a superposed stationary monsoon wave
- 27 Growth of monsoon disturbances over western India
- 28 Topographic Rossby waves in the summer monsoon
- Part III The physics and dynamics of the Indian Ocean during the summer monsoon
- Part IV Some important mathematical modelling techniques
- Part V Storm surges and flood forecasting
- Index
Summary
Active monsoon epochs over western India are often associated with cyclonic disturbances most marked in the midtroposphere. In order to understand the mechanism of their growth, linear barotropic, baroclinic and combined barotropic–baroclinic stability analyses of the mean flow in this region have been carried out. The potential vorticity of the mean flow shows extreme values in the region of the midtropospheric shear zone. The analyses yield barotropically unstable modes (i) at 700, 600, 500 mb and (ii) at 200 mb, with wavelengths of 20 to 30 degrees of longitude and doubling times of 3 to 4 days. Combined barotropicbaroclinic stability analyses using a 2-level quasi-geostrophic model yield essentially the same upper- and lower-tropospheric barotropically unstable modes, with only a marginal effect due to the presence of baroclinicity.
Introduction
There seem to be certain parts of the monsoon region from southeast Asia to western India which are particularly cyclogenetic. Shukla (1977) and Keshavamurty et al. (1977) have carried out a general stability analysis of the monsoon zonal flow. It turns out that the zonal wind profile over western India shows some slightly different features compared to that, say, over southeast Asia. In the former longitudes, the heat low over northwest India–Pakistan is overlain by anticyclonic flow in the midtroposphere, so that there is an east–west shear zone in the middle levels. This feature is not so well marked over other longitudes in the monsoon region.
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- Monsoon Dynamics , pp. 415 - 428Publisher: Cambridge University PressPrint publication year: 1981