First ISCCP Regional Experiment (FIRE) Atlantic Stratocumulus Transition Experiment (ASTEX) Marine Aerosol Gas Exchange (MAGE) Tetroon

The First ISCCP Regional Experiments have been designed to improve data products and cloud/radiation parameterizations used in general circulation models (GCMs). Specifically, the goals of FIRE are (1) to improve the basic understanding of the interaction of physical processes in determining life cycles of cirrus and marine stratocumulus systems and the radiative properties of these clouds during their life cycles and (2) to investigate the interrelationships between the ISCCP data, GCM parameterizations, and higher space and time resolution cloud data. To-date, four intensive field-observation periods were planned and executed: a cirrus IFO (October 13 - November 2, 1986); a marine stratocumulus IFO off the southwestern coast of California (June 29 - July 20, 1987); a second cirrus IFO in southeastern Kansas (November 13 - December 7, 1991); and a second marine stratocumulus IFO in the eastern North Atlantic Ocean (June 1 - June 28, 1992). Each mission combined coordinated satellite, airborne, and surface observations with modeling studies to investigate the cloud properties and physical processes of the cloud systems.The ASTEX/MAGE experiment is a multinational effort to improve our capability for studying cloud-chemistry interactions and the air/sea fluxes that affect them. The primary purpose of ASTEX (with which MAGE collaborated) was to study the factors influencing the formation and dissipation of marine clouds. The specific goals of the MAGE atmospheric chemistry experiment in ASTEX included:- Develop and test a Lagrangian strategy for studying chemical and meteorological evolution in a tagged airmass, using ships, balloons, and aircraft.- Develop and test new techniques for estimating trace-gas and aerosol fluxes across the air/sea interface by comparison with traditional approaches.- Evaluate the impact of marine and continental aerosols on the formation and dissipation of stratocumulus clouds.- Compare the impacts of natural and anthropogenic sulphur, halogens, and hydrocarbons on marine aerosol chemistry.- Gain experience with multi-national and multi-agency field experiments as a means for addressing global tropospheric chemistry issues. The North Carolina State University tetroons were launched from the ship Oceanus in support of the FIRE-ASTEX observational program, conducted in the eastern North Atlantic during the month of June 1992. Special constant density balloons were launched and then tracked for 48 hours -- with the idea that they were tracking a single parcel of air. The parameter #sats gives the number of GPS satellites available for positioning. Four satellites are necessary to determine altitude, otherwise the last available altitude from four satellites is assumed to remain constant, so that the horizontal location can be triangulated from three satellites. An altitude is always given in the file, so care should be taken as to its use.Each tetroon attempted to fix its location once every 5 minutes of operation. Each tetroon was given an offset in transmission time during the 5 minute period in which to transmit its location in order to allow all tetroons to broadcast on the same frequency. The time at which a position fix was made and the relevant location information is provided for each tetroon. In the event no fix was possible due to the satellite constellation configuration, number or signal strength, no position was transmitted. Each position was retransmitted at 1/2 hour increments for seven hours to attempt to obtain the maximumamount of data, even for periods when aircraft were not in the area of transmission.