PEM Tropics B

The NASA Pacific Exploratory Mission- Tropics B (PEM Tropics B) was a study of the chemistry in the tropical and southern hemisphere Pacific atmosphere.  This program was flown on the NASA P-3B and the NASA DC-8.  Our instrument was on the P-3B and studied SO2 and DMS in the lower atmosphere.

    Our primarily objective was to study the atmospheric chemistry of dimethyl sulfide (DMS) that is emitted to the atmosphere from the ocean and is the primary source of sulfur in the remote marine atmosphere.  Recall that every cloud droplet requires a preexisting aerosol particle on which to form and over the remote ocean they form on sulfuric acid particles produced from the oxidation of DMS.

For the first time we simultaneously observed DMS, SO2, H2SO4 and OH that clearly showed that the our models of photochemistry of these species was fundamentally correct.  However, just how the H2SO4 particles are formed from the gas phase and how these particles actually influence cloud formation is still unresolved.  

This chemistry is very important because it strongly influences cloud properties and these cloud particles are important in determining how much of the suns radiation reaches the earth surface.  The radiation reaching the earth's surface has an important influence on  the temperature of the earth which is clearly important for all life on earth.

 
Dr. Don Thornton in charge of the mission operating the
GCMS instrument.

P-3B aircraft  parked at Nasa's Wallops Flight Facility