Tropical waves observed by balloon-borne GPS Radio Occultation measurements of Strateole-2 campaign over equatorial area

Abstract:

The international Strateole-2 campaign successfully launched the first group of five super-pressure balloons in Nov-Dec 2019. One balloon carrying a Radio OCcultation v2 (ROC2) multiple-frequency GNSS receiver flew eastward over the equatorial region for two months at 20 km altitude. The receiver performed Radio Occultation (RO) measurements continuously during the flight. There are ~40-50 RO profiles retrieved daily along the flight track. The profiles sample the atmosphere underneath the flight track from balloon height down to 8-10 km altitude. Due the asymmetric geometry of the balloon and GNSS satellites, the profiles slant horizontally up to 500 km to both sides of the track. Comparisons with operational radiosondes data over Indonesia show excellent agreement. The temperature measurements of a train of nearly-parallel RO profiles are used to deduce wave structures, with background temperature determined by averaging the temperature retrieved from space-borne RO profiles (COSMIC and COSMIC-2) over a larger area. Wave structures and information are identified from the correlation of temperature perturbations of multiple nearby profiles. In addition to the RO profiles, the in-situ measurements of temperature, pressure and winds, retrieved from the quasi-Lagrangian motion of balloon, are also used to identify wave patterns.