Journal of Earth System Science

, Volume 112, Issue 2, pp 131–146

Some salient features of the atmosphere observed over the north Bay of Bengal during BOBMEX

  • G. S. Bhat
Article

Abstract

This paper describes the near surface characteristics and vertical variations based on the observations made at 17.5‡N and 89‡E from ORV Sagar Kanya in the north Bay of Bengal during the Bay of Bengal Monsoon Experiment (BOBMEX) carried out in July–August 1999. BOBMEX captured both the active and weak phases of convection. SST remained above the convection threshold throughout the BOBMEX. While the response of the SST to atmospheric forcing was clearly observed, the response of the atmosphere to SST changes was not clear. SST decreased during periods of large scale precipitation, and increased during a weak phase of convection. It is shown that the latent heat flux at comparable wind speeds was about 25–50% lower over the Bay during BOBMEX compared to that over the Indian Ocean during other seasons and tropical west Pacific. On the other hand, the largest variations in the surface daily net heat flux are observed over the Bay during BOBMEX. SST predicted using observed surface fluxes showed that 1-D heat balance model works sometime but not always, and horizontal advection is important. The high resolution Vaisala radiosondes launched during BOBMEX could clearly bring out the changes in the vertical structure of the atmosphere between active and weak phases of convection. Convective Available Potential Energy of the surface air decreased by 2–3 kJ kg-1 following convection, and recovered in a time period of one or two days. The mid tropospheric relative humidity and water vapor content, and wind direction show the major changes between the active and weak phases of convection.

Keywords

Monsoon air-sea coupling tropical convection boundary layer 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Betts A K 1976J. Atmos. Sci. 33 1008–1020CrossRefGoogle Scholar
  2. Bhat G S 2001Geophys. Res. Lett. 28 987–990CrossRefGoogle Scholar
  3. Bhat G S 2002J. Geophys. Res. 107 10.1029/2001 JD000382Google Scholar
  4. Bhat G S, Ameenulla S, Venkataramana M and Sengupta K 2000Proc. Indian Acad Sci. Earth Planet. Sci. 109 229–237Google Scholar
  5. Bhat G S, Gadgil S, Harish Kumar P V, Kalsi S R, Madhusoodanan P, Murty V S N, Prasada'Rao C V K, Ramesh Babu V, Rao L V G, Rao R R, Ravichandran M, Reddy K G, Sanjeeva Rao P, Sengupta D, Sikka D R, Swain J and Vinayachandran P N 2001Bull. Amer. Meteor. Soc. 82 2217–2243CrossRefGoogle Scholar
  6. Bhat G S, Thomas M A, Raju J V S and Chandrasekhara C P 2003Boundary Layer Meteorol. 106 263–281CrossRefGoogle Scholar
  7. Bradley E F, Godfrey J S, Coppin P A and Butt J A 1993J. Geophys. Res. 98C 22521–22532Google Scholar
  8. Chen S S and Houze R A Jr. 1997Q. J. R. Meteor. Soc. 123 357–388CrossRefGoogle Scholar
  9. Fairall C W, Bradley E F, Rogers D P, Edson J B and Young G S 1996J. Geophys. Res. 101C 3747–3764Google Scholar
  10. Fairall C W, Bradley E F, Godfrey J S, Wick G A, Edson J B and Young G S 1996aJ. Geophys. Res. 101C 1295–1308Google Scholar
  11. Fein J S and Kuettner J P 1980Bull. Amer. Meteor. Soc. 61 461–474Google Scholar
  12. Gadgil S, Joseph P V and Joshi N V 1984Nature 312 141–143CrossRefGoogle Scholar
  13. Gambheer A V and Bhat G S 2001Meteorol. Atmos. Phys. 78 215–225CrossRefGoogle Scholar
  14. Godfrey J S, Houze R A Jr, Johnson R H, Lukas R, Redelsperger J L, Sumi A and Weller R 1998J. Geophys. Res. 103C 3747–3764Google Scholar
  15. Graham N E and Barnett T P 1987Science 238 657–659CrossRefGoogle Scholar
  16. Hosom D S, Weller R A, Payne R E and Prada K E 1995J. Atmos. Oceanic Technol. 12 527–540CrossRefGoogle Scholar
  17. Kingsmill D E and Houze R A Jr. 1999Q. J. R. Meteorol. Soc. 125 1209–1229CrossRefGoogle Scholar
  18. Knupp K R and Cotton W R 1985Rev. Geophys. 23 183–215Google Scholar
  19. Krishnamurti T N 1985Mon. Weather Rev. 113 1590–1626CrossRefGoogle Scholar
  20. Krishnamurti T N, Oosterhof D K and Mehta A V 1988J. Atmos. Sci. 45 1304–1322CrossRefGoogle Scholar
  21. Mitra A P 1999Current Science 76 886–889Google Scholar
  22. Mohanty U C and Das S 1986Proc. Indian Natn. Sci. Acad. 52 625–640Google Scholar
  23. Moncrief M W and Miller M J 1976Q. J. R. Meteorol. Soc. 102 373–394CrossRefGoogle Scholar
  24. Paulson C A and Simpson J J 1981J. Geophys. Res. 86 11044–11054Google Scholar
  25. Premkumar K, Ravichandran M, Kalsi S R, Sengupta D and Gadgil S, 2000Current Science 78 323–331Google Scholar
  26. Vinayachandran P N, Murty V S N and Ramesh Babu V 2002J. Geophys. Res. (Oceans)107 10.1029/2002 JC001669Google Scholar
  27. Waliser D A, Graham N E and Gautier C 1993J. Climate 6 1405–1423Google Scholar
  28. Webster P J and Lukas R 1992Bull. Amer. Meteor. Soc. 73 1377–1416CrossRefGoogle Scholar
  29. Webster P J, Bradley E F, Fairall C E, Godfrey J S, Hacker P, Lucas R, Serra Y, Houze R A Jr., Humman J M, Lawrence T D M, Russel C A, Ryan M N, Sahami K and Zuidema P 2002Bull. Amer. Meteor. Soc. 83 1603–1630CrossRefGoogle Scholar
  30. Zeng X, Zhao M and Dickinson R E 1998J. Climate 11 2628–2644CrossRefGoogle Scholar

Copyright information

© Indian Academy of Sciences 2003

Authors and Affiliations

  • G. S. Bhat
    • 1
  1. 1.Centre for Atmospheric and Oceanic SciencesIndian Institute of ScienceBangaloreIndia

Personalised recommendations