Temporal Variability of Surface Fluxes and Mixed Layer Response at 15.5 N, 61.5 E over a Monsoonal Cycle

ALBERT S. FISCHER Massachusetts Institute of Technology
ROBERT A. WELLER Woods Hole Oceanographic Institute

Introduction and Objectives

    Winds over the Arabian Sea are dominated by strong and steady monsoonal patterns with large spatial scales. During the summer the southwest monsoon produces an air flow known as the Findlater Jet, with high wind stress curl and upwelling to the north and west, and downwelling to the south and east. Late summer sea surface temperatures are observed to be cooler than those in the spring. In the winter northeast monsoon, the wind reverses direction and is weaker, but is still quite steady. The objectives of this observational program were to make quantitative assessments of the surface and lateral fluxes of heat, salt, and momentum, and to better ascertain their role in mixed layer dynamics.

    High-quality coincident time series of the atmospheric forcing and upper ocean resonse at 15 30' N, 61 30' E in the Arabian Sea were obtained during the winter and summer monsoons. A surface mooring was deployed from 15 October 1994 through 20 October 1995, part of an array just south of the climatological wind maximum. The mooring had a full suite of meteorological instruments, and collected subsurface temperature, salinity, and current data. Drs. John Marra, Tom Dickey, Van Holliday, and Chris Langdon attached additional bio-optical instrumentation.

    The mooring had two full sets of meteorological sensors, including wind speed and direction, sea surface temperature, air temperature, incoming short wave and long wave radiation, barometric pressure, relative humidity and precipitation. Data was transmitted to WHOI in real-time by satellite, and was recorded every 450 seconds. The buoy hull also supported six temperature loggers (Tpods) in the upper 2.5 m, each protected by a radiation shield. The mooring line carried a wide variety of instruments in the upper 300 m. These included vector-measuring current meters (VMCMs), which also measured temperature, conductivity and temperature sensors (SEACATs), 4 muti-variable moored system (MVMS) sensors measuring velocity, temperature, photosynthetically available radiation and transmissivity, and further temperature loggers (Tpods). Subsurface instruments recorded every 225-900 seconds.

Figure 1a. Mooring location.

Figure 1b. A photograph of the Arabian Sea surface mooring, an instrumented 3 m discus buoy.

Figure 1c. A mooring diagram showing the positions of the various instruments (Jayne Doucette/WHOI Graphics).

Surface Meteorology and Fluxes

Observations of the Mixed Layer

1D Budget Calculations

1D PWP Model Calculations



Selected References

Contact Information

This is the web version of a poster originally displayed at the 1996 AGU/ASLO Ocean Sciences conference (poster OS11A-13). Created 26 March 1996, A. Fischer.