3RD SOVIET-AMERICAN GASES AND AEROSOLS (SAGA-3) EXPERIMENT - OVERVIEWAND METEOROLOGICAL AND OCEANOGRAPHIC CONDITIONS

The primary goal of the third joint Soviet-American Gases and Aerosols (SAGA 3) experiment was to study trace gases and aerosols in the remo te marine boundary layer. SAGA 3/leg 1 took place from February 13 to March 13, 1990, aboard the former Soviet R/V Akademik Korolev and cons isted of five equatorial transects (designated transects 1 through 5) between 15-degrees-N and 10-degrees-S on a cruise track from Hilo, Haw aii, to Pago-Pago, American Samoa. Specific objectives were to study ( 1) the oceanic distribution and air-sea exchange of biogenic trace gas es; (2) photochemical cycles of C-, S-, and N-containing gases in the marine boundary layer; (3) the distribution of aerosol particles in th e marine boundary layer and their physical and chemical properties; (4 ) interhemispheric gradients and latitudinal mixing of trace gases and aerosols; and (5) stratospheric aerosol layers. SAGA 3/leg 2 continue d from March 17 to April 7, 1990, with one more equatorial transect be tween American Samoa and the northern coast of the Philippines (transe ct 6) followed by a final transect to Singapore (transect 7). During l eg 2, most former Soviet measurements continued, but with the exceptio n of measurements of nitrous oxide (N2O) and selected halocarbons in t he air and surface waters all American measurements ceased. This paper briefly summarizes the chemical measurements made by SAGA 3 investiga tors and presents in some detail the meteorological and hydrological c haracteristics encountered during SAGA 3. The meteorological analysis is based on atmospheric soundings of temperature, humidity, winds, sea surface temperature, postcruise back trajectories of winds, and satel lite imagery. In general, the meteorology during SAGA 3 was typical of the location and time of year. Exceptions to this include an incipien t E1 Nino that never developed fully, a poorly defined ITCZ on 4 of 6 equator crossings, wind speeds that were 20% greater than the decadal mean, a convective event that brought midtropospheric air to the surfa ce (on Julian day 59), and transport of northern hemispheric air to 18 -degrees-S during a synoptic scale tropical disturbance