Stratospheric gravity wave potential energy and tropospheric parameters relationships over South America: a study using COSMIC-2 and METOP radio occultation measurements

Abstract

Using COSMIC-2 and METOP radio occultation measurements during the years 2020 and 2021, the study presents the first direct and independent relationship between the potential energy (Ep) in the stratosphere, precipitable water vapour (PWV), tropopause heights (TPH), and cold-point heights (CPH) over South America. The South American continent comprises the tropical region, the Andes Mountain range, and mid-latitude climates. The seasonal mean of the potential energy (Ep), the PWV, and the tropopause parameters height (TPH and CPH) were obtained to investigate the relationship between the stratospheric gravity wave (SGW) Ep and the tropospheric parameters (PWV, TPH, and CPH). Around the Andes Mountains to the east, there is significantly less water vapour (PWV < 10 mm) and a relatively high gravity wave Ep (Ep > 8 kJ kg−1). A good correlation of variability was found between the PWV and the lower SGW Ep in summer over the tropical region (± 20◦). Generally, good and strong correlations were observed in the summer and spring, with negative/no correlations in the winter in 2020 and 2021. Also, good and strong correlations between SGW, PWV, and TPH were observed in the summer at 20 oN- 10 oN in 2020 and 2021. Our result demonstrated the possibility that convective activity was a major driver of the tropical gravity waves over South America. In the subtropical (30 ∘ –40 ∘) region, especially in the winter, the tropospheric parameters make little or no contribution to gravity wave activity in the region. The CPH generally showed a no/negative with SGW over the South American tropics. The SGW activities in the tropical region showed an impact on the structure of the tropopause parameters, which could be a result of the convective activity in this region. Graphical Abstract: [Figure not available: see fulltext.]