The TWERL Experiment

Abstract

One of the experiments aboard the Nimbus-6 satellite was a data collection and Doppler location system used in conjunction with a fleet of instrumented superpressure balloon platforms. The acronym TWERLE stands for Tropical Wind, Energy Conversion, and Reference Level Experiment, after its principal scientific objectives. A brief system description is given together with a discussion of the launch, in the tropics and Southern Hemisphere, of the 400 balloon platforms. The platforms were designed to float at a nominal pressure of 150 mb. A number of preliminary scientific results are discussed in different subject areas. The large, or hemispheric scale, dispersion of the platforms exhibited definite nonrandomness in that clustering in certain regions of the tropics occurred while other regions were avoided. Owing to the fact that the balloons drift with the wind on a surface of constant density, the basic data are quasi-Lagrangian in nature. Some interesting aspects of such data are discussed. Notable was the fact that ~2 5% of the balloons launched from Christchurch, New Zealand (44°S), at some time in their history entered the Northern Hemisphere. The TWERLE platforms carried sensors for measuring pressure, temperature, and altitude. Such sensor data permit investigations of various kinds of wave motion that influence the balloon platforms. Among those motions investigated and discussed are gravity waves, orographic lee waves, and forced wave flow over developing convective clouds. The subjects covered here are intended to demonstrate the extraordinary flexibility and utility of an instrumented superpressure balloon system using a satellite vehicle for data collection and for location determination.