ROSSBY-GRAVITY WAVES IN TROPICAL TOTAL OZONE

Randel [1992] has recently reported evidence for Rossby-gravity waves in tropical data fields produced by the European Centre for Medium Range Weather Forecasts (ECMWF). The purpose of this paper is to show that similar features axe observable in fields of total column ozone from the Total Ozone Mapping Spectrometer (TOMS) satellite instrument. The observed features are episodic, have zonal (east-west) wavelengths Of approximately 6,000-10,000 km and oscillate with periods of 5-10 days. The modes exhibit westward phase progression and eastward group velocity. A simple linear model is used to estimate the magnitude of total ozone perturbations induced by Rossby-gravity waves. The model is able to account for the magnitude of observed TOMS features as well as their asymmetry about the equator. The significance of finding Rossby-gravity waves in total ozone fields is that (1) the report of similar features in ECMWF tropical fields is corroborated with an independent data set and (2-) the TOMS data set is demonstrated to possess surprising versatility and sensitivity to relatively smaller scale tropical phenomena.