STERAO-A: Stratosphere-Troposphere Experiments: Radiation, Aerosols, and Ozone (STERAO)

Summary

The Stratospheric-Tropospheric Experiment: Radiation, Aerosols, and Ozone (STERAO) series of projects was initiated to address these important problems. STERAO-A (Deep Convection and the Composition of the Upper Troposphere and Lower Stratosphere) was the first of three projects to be followed by two others: one on aerosols and cirrus cloud properties and another on photochemistry of the near-tropopause region.

STERAO-A was conducted in Northeastern Colorado during June and July of 1996 with aircraft observations concentrated in a 4-week period from mid-June to mid-July. Colorado was chosen because of a high frequency of storms in the area ranging from simple air mass to multicell, to supercell thunderstorms; because it is close to Denver, CO, with suitable locations for aircraft operation; and because the Colorado State University (CSU) CHILL radar was located in the area near Greeley, CO. The Operations Center for the project was located in the radar control van at the CSU-CHILL radar site. During the 4-week period when aircraft were available, measurements were obtained in 14 storms with either one or both aircraft. The project also collected combined radar and lightning data daily from mid-June to early September, thus providing measurements on both intracloud (IC) and cloud-to-ground (CG) lightning for a wide variety of storm types of the central high plains.

STERAO-A closely coordinated chemical, dynamical, electrical, and microphysical observations to investigate the production of NOx by lightning, the transport and redistribution of chemical species in the troposphere by thunderstorms, and the temporal evolution of intracloud and cloud-to-ground lightning for evolving storms on the Colorado high plains. Major observations included airborne chemical measurements in the boundary layer, middle and upper troposphere, and thunderstorm anvils; airborne and ground-based Doppler radar measurements; measurement of both intracloud (IC) and cloud-to-ground (CG) lightning flash rates and locations; and multiparameter radar and in situ observations of microphysical structure. Cloud and mesoscale models were used to synthesize and extend the observations.