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
14 - Medium-range forecasting of monsoon rains
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
For the planning of agricultural operations as well as the operation of large dams and reservoirs, medium-range forecasts of precipitation covering a period of 5 to 10 days are of great potential value.
Medium-range forecasting of monsoon activity requires first the identification of slowly evolving changes in the monsoon circulation. A study of periodicities in the monsoon circulation by power spectrum analysis of the zonal and meridional components of winds shows the existence of periodicities of 6 to 8 days' duration. Synoptic experience also indicates that each spell of active monsoon conditions is of about one week's duration.
A recent study of the monsoon circulation during Phase II of MONSOON-77 (25 June to 2 August 1977) revealed that during a weak phase of the monsoon a second trough formed in the south Bay of Bengal in the lower troposphere, while the trough in the north persisted. Low-pressure systems formed in this low-latitude trough and caused rainfall over the southern peninsula. This circulation pattern resulted in two distinct belts of excess rainfall, one in the north and another in the south, with relatively less rainfall over central parts. During the course of a week, the southern trough shifted northwards and resulted in the initiation of another active spell of monsoon rains over central parts.
Some of the observed oscillations of the monsoon circulation seem to be linked with features of the hemispheric circulation as revealed by variations of the zonal index. […]
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- Monsoon Dynamics , pp. 221 - 236Publisher: Cambridge University PressPrint publication year: 1981