The relationship between ITCZ and the Equatorial Stratospheric Gravity Waves inferred from Radio Occultation Measurements

Abstract The GNSS radio occultation (RO) temperature and refractivity data obtained from COSMIC-1, COSMIC-2, and METOP satellites for 2011-2021 was used to investigate the occurrence of equatorial stratospheric gravity waves (ESGWs) and their relationship with the intertropical convergence zone (ITCZ), as well as the ITCZ as a significant source of ESGWs. The ESGWs were inferred using the RO temperature profiles and the GW potential energy (Ep). The ITCZ and the peak concentrated Ep are found by taking the maximum point of the meridional refractivity and the Ep at each longitude using a Gaussian fit. The ITCZ location varies latitudinally by 10 between December-January-February (DJF) and June-July-August (JJA), and by 5 between September-October-November (SON) and March-April-May (MAM) over the world landscape and oceanic regions. The position and strength of the ITCZ vary from year to year. The inter-annual variability migrated about 5 - 15 north and south. The global ESGW Ep maxima displayed seasonal changes similar to the ITCZ. The global ESGW Ep maxima were more consistent in the NH and SH, with a significantly smaller gap than the ITCZs. Two convergences in the Ep maxima over the western Pacific and South America are suggested to be connected to the double ITCZ and El Nin˜o Southern Oscillation (ENSO), respectively. The study’s findings indicate a strong correlation between the ITCZ and Ep maxima in various seasons, implying that the ITCZ plays a significant role in driving the ESGWs. Furthermore, the Madden-Julian Oscillation (MJO) could impact atmospheric refractivity and the ESGW Ep.