Air-Sea Interaction in the Austral-Asian Monsoon:

The Joint Air-Sea Monsoon Investigation (JASMINE-99) Pilot Study

Program Description

The Joint Air-Sea Monsoon Investigation (JASMINE) is based on the hypothesis that intraseasonal variability of the Asian-Australasian monsoon system is the result of coupled ocean-atmosphere interaction in a region of very large cross-equatorial surface pressure gradient. JASMINE is presently planned in two phases: a pilot study in 1999 and a main experiment in 2000. The overall aim of these process studies in the North Indian Ocean is to determine the dynamic and thermodynamic structure of the active and break periods of the monsoon (i.e., the intraseasonal variability) and link them to variations in sea surface temperature and coupled ocean-atmospheric interactions. The maximum amplitude of the variation in monsoon precipitation occurs at approximately 90-E and 13-N. This process study is in direct support of the major scientific objectives of the Global-Ocean-Atmosphere-Land System (GOALS) Program. GOALS seeks to increase the prediction of elements of the monsoon circulation. Thus, the processes that produce the intraseasonal variations of the Asian-Australasian monsoon are central scientific issues for GOALS. Details are provided in the document "Intraseasonal Variability of the South Asian Monsoon System: The Concept of JASMINE" by P. J. Webster and Collaborators (contact P. Webster at for a copy).

Measurement Strategy

The particular purposes of the 1999 cruise are to determine the ocean-atmosphere interactions during these intraseasonal variations, document the changes that occur in the upper ocean and lower troposphere during the transitions, and provide background information for the more comprehensive study to follow. Thus, besides measuring the elements of the surface heat budget, the upper ocean and lower troposphere will also be profiled with a variety of remote and in situ sensors. On the atmospheric side, meteorological radars will monitor cloud, precipitation, and disturbance structures during the time on station. A strong emphasis will be placed on measurements of atmospheric boundary-layer dynamical properties and structures across the monsoon system. These are key problems in numerical modeling of coupled air-sea processes. The suite of instruments required will be closely equivalent to those planned for the joint DOE/NOAA ARM experiment being planned for the vicinity of Nauru. On the ocean side, a strategy involving TOGA- COARE style box or butterfly patterns centered at 90-E and 10 N with a combination of TAO/IMET buoys is being developed to examine heat and salt budgets. E-W transects near the equator will be obtained in the going to and from the experimental area. There has never been a high-quality study in this region in this season; T and S structures are thought to be very shallow and should have a strong effect on air-sea fluxes.

It is planned that the cruise will take part in an intensive observation period of a year-long monitoring program along a line from the Bay of Bengal to south of the equator. Atlas TAO moorings and a WHOI IMET buoy will be deployed along this line. It is also planned to deploy a research aircraft along the mooring line during the intensive observation phase thus providing a context and connection for the buoys and ship. The Australian R/V Franklin will participate in the October/November time frame to recover/service buoys and take meteorological and oceanographic data.

Relevance to NOAA's Mission and Relationship to Strategic Plan Elements

The emphasis of this program is directly relevant to the Seasonal to Interannual Forecast element. There are also implications for the both Decadal to Centennial Change and Short Term Forecast elements.

Key Co-Investigators

ETL Air-Sea Interaction Group

Dr. P. J. Webster, University of Colorado

Drs. Robert Houze and Sandra Yuter, University Of Washington

Drs. Peter Hacker and Roger Lukas, University of Hawaii

Dr. Robert Weller, WHOI

Dr. Stuart Godfrey, CSIRO Marine Research (Australia)

Dr. Frank Bradley, CSIRO Land and Water (Australia)

Drs. Bates and Quinn, PMEL