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
- 1 Teleconnections of rainfall anomalies in the tropics and subtropics
- 2 Northern summer planetary-scale monsoons during drought and normal rainfall months
- 3 The annual oscillation of the tropospheric temperature in the northern hemisphere
- 4 Summer mean energetics for standing and transient eddies in the wavenumber domain
- 5 Monitoring the monsoon outflow from geosynchronous satellite data
- 6 Predictability of monsoons
- 7 A review of general-circulation model experiments on the Indian monsoon
- 8 Simulation of the Asian summer monsoon by an 11-layer general-circulation model
- 9 Analysis of monsoonal quasi-stationary systems as revealed in a real-data prediction experiment
- 10 A model of the seasonally varying planetary-scale monsoon
- 11 Wave interactions in the equatorial atmosphere – an analytical Study
- Part II The summer monsoon over the Indian subcontinent and East Africa
- 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
2 - Northern summer planetary-scale monsoons during drought and normal rainfall months
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
- 1 Teleconnections of rainfall anomalies in the tropics and subtropics
- 2 Northern summer planetary-scale monsoons during drought and normal rainfall months
- 3 The annual oscillation of the tropospheric temperature in the northern hemisphere
- 4 Summer mean energetics for standing and transient eddies in the wavenumber domain
- 5 Monitoring the monsoon outflow from geosynchronous satellite data
- 6 Predictability of monsoons
- 7 A review of general-circulation model experiments on the Indian monsoon
- 8 Simulation of the Asian summer monsoon by an 11-layer general-circulation model
- 9 Analysis of monsoonal quasi-stationary systems as revealed in a real-data prediction experiment
- 10 A model of the seasonally varying planetary-scale monsoon
- 11 Wave interactions in the equatorial atmosphere – an analytical Study
- Part II The summer monsoon over the Indian subcontinent and East Africa
- 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
In this paper the 200 mb flow regimes during a drought year (1972) are contrasted with those during a normal rainfall year (1967) over the global tropics for the northern summer months. It is shown that the deficient rainfall over central India and western Africa during 1972 may be related to the following: (i) warm sea-surface temperatures over the equatorial Pacific; (ii) an excessive number of typhoon days over the equatorial Pacific; (iii) strong east-northeasterlies over the equatorial eastern Indian Ocean (related to upper-level outflows from the typhoons); (iv) a weaker tropical easterly jet; (v) a weaker meridional pressure gradient over India; (vi) a weaker Tibetan High; (vii) a south-eastward shift over the major circulation patterns as well as of several dynamical parameters; (viii) a weaker vertical wind shear and a weaker measure of the combined barotropicbaroclinic instability over west Africa; and (ix) weaker westward steering for rain-producing disturbances over India and a consequent stronger influence of the mountains.
A sequential interrelationship of the above aspects of the drought problem are discussed in this paper.
Introduction
The monsoonal rainfall over south Asia and west Africa undergoes interannual variations. Although some of the anomalous periods have more of a regional character, i.e., a period of drought over parts of a continent may not occur at the same period in other regions, there do exist periods of widespread drought that extend from west Africa to India. Such droughts occurred during the summers of 1877, 1899, 1918 and 1972.
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- Monsoon Dynamics , pp. 19 - 48Publisher: Cambridge University PressPrint publication year: 1981
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