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
- Part III The physics and dynamics of the Indian Ocean during the summer monsoon
- 29 Observations of the Somali Current and its relationship to the monsoon winds
- 30 Structure of currents and hydrographic conditions in the western equatorial Indian Ocean during the summer monsoon
- 31 Recent observations in the equatorial Indian Ocean
- 32 Sea temperature variations in the northeastern Arabian Sea in relation to the southwest monsoon
- 33 Heat budget of the north Indian oceanic surface during MONSOON-77
- 34 The energy budget at selected stations over the north Indian Ocean during MONSOON-77
- 35 Observations of coastal-water upwelling around India
- 36 A numerical study of surface cooling processes during summer in the Arabian Sea
- 37 Maximum simplification of nonlinear Somali Current dynamics
- 38 Laboratory modelling of the oceanic response to monsoonal winds
- Part IV Some important mathematical modelling techniques
- Part V Storm surges and flood forecasting
- Index
31 - Recent observations in the equatorial Indian Ocean
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
- Part III The physics and dynamics of the Indian Ocean during the summer monsoon
- 29 Observations of the Somali Current and its relationship to the monsoon winds
- 30 Structure of currents and hydrographic conditions in the western equatorial Indian Ocean during the summer monsoon
- 31 Recent observations in the equatorial Indian Ocean
- 32 Sea temperature variations in the northeastern Arabian Sea in relation to the southwest monsoon
- 33 Heat budget of the north Indian oceanic surface during MONSOON-77
- 34 The energy budget at selected stations over the north Indian Ocean during MONSOON-77
- 35 Observations of coastal-water upwelling around India
- 36 A numerical study of surface cooling processes during summer in the Arabian Sea
- 37 Maximum simplification of nonlinear Somali Current dynamics
- 38 Laboratory modelling of the oceanic response to monsoonal winds
- Part IV Some important mathematical modelling techniques
- Part V Storm surges and flood forecasting
- Index
Summary
Recent velocity profile data for the western equatorial Indian Ocean are presented and discussed. These display a very low frequency variability of small vertical scales. Wunsch's (1977) theoretical model of a forced equatorial response at the annual period is shown to provide a rational explanation of the phenomenon.
Introduction and historical background
The oceanographic response of the western Indian Ocean to the atmospheric monsoon regime is a complicated one, both from the observational and theoretical points of view. Several phenomena have a clearly documented relationship to the monsoon forcing although many of the details are not clearly understood. The most dramatic of these monsoon phenomena, the Somali Current, has been discussed by Swallow in Chapter 29 of this book.
In the open, equatorial Indian Ocean two phenomena exist whose seasonal variability is clearly associated with the monsoon–the equatorial undercurrent and the equatorial surface jet. Recent observations suggest there may be other monsoon-related currents at greater depths.The equatorial undercurrent is a permanent feature of both the Atlantic and Pacific Oceans (Philander, 1973) and is generally believed to be associated with the persistent trade winds from the east. This westward stress at the surface, and corresponding difference in elevation of the sea surface, is balanced by a zonal pressure gradient between the boundaries. Indian Ocean such a zonal pressure gradient can only be established by the northeast monsoon. The observations (Taft and Knauss, 1967; Swallow, 1967; Knox, 1976; Kort et al., 1975) have shown an undercurrent only during the latter part of the northeast monsoon, with large variations in strength from year to year.
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- Monsoon Dynamics , pp. 465 - 480Publisher: Cambridge University PressPrint publication year: 1981
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