SESAME: Severe Environmental Storms and Mesoscale Experiment

Summary

During the spring of 1979, NSF, NOAA, NASA, other Governmental Agencies, and 14 Universities participated in a joint field project called the Severe Environmental Storms and Mesoscale Experiment (SESAME) to learn more about the structure, meso-synoptic processes, and dynamics of severe convective mesoscale systems. The NASA component was a continuation of a series of similar experiments, conducted during the years 1964-1978, under NASA’s Atmospheric Variability Experiment (AVE) Program. Three hourly regional scale rawinsonde data, along with other specialized data (e.g. aircraft, Doppler radar, satellite, surface, etc.) were collected during AVE-SESAME-79 to accomplish the scientific goals and further studies. These included: (1) the interaction of atmospheric scales of motion; (2) the structure and organization of mesoscale systems; and (3) developing a general understanding of parameterization for numerical, statistical studies, and prediction of severe convective weather.  In particular, the phenomena associated with such severe convective activity included tornadoes, damaging winds, hail, floods, turbulence, etc., that affect property and personal safety. Two NCAR aircrafts, the QueenAir A-80, and the Sabreliner Model 60, flew missions to: (1) investigate the kinematic and thermodynamic structure of thunderstorm environments at low and mid-levels as represented by the thunderstorms of Oklahoma; and (2) explore the cross-sectional structure of the dry line through the use of a saw-tooth and stepladder pattern as well as to observe mixed layer development as associated with thunderstorms.

The regional-scale experiments consisted of 24-h periods of upper-air observation involving 23 National Weather Service (NWS) rawinsonde sites and 19 supplemental rawinsonde sites taking measurements at 3-h intervals during intensive observing or experiment periods. Rapid scan visual and infrared imagery was acquired by GOES satellites, along with TIROS-N and NIMBUS-G sensor data. Special conventional and special Doppler radar data were obtained from stations located in the experiment area. A dense special surface network of NCAR’s Portable Automated Mesonet (PAM) and NOAA’s National Severe Storm Laboratory (NSSL) Stationary Automated Mesonet (SAM) were located in central Oklahoma. In addition, special observations were made by a NOAA/NSSL storm electricity measurement site in Norman, OK, three (3) NSSL intercept photography teams, and volunteer observer reports.