Long Period Waves and Oscillations Over Costa Rica, a Tropical Station

Seasonal, annual and interannual variations of Ozone Mixing Ratio (OMR) have been studied for 12 years, from balloonsondes and Ozonesondes that were launched over Costa Rica (10oN, 83.4oW), a tropical station, as part of Southern Hemisphere Additional Ozonesondes (SHADOZ) network. It was found that near tropopause region there exists prominent peak of OMR during July month for most of the years. Lomb-Scargle Periodogram (LSP) analysis has been applied for the years 2005-2017 to identify the wave activities and found that Quasi Biennial Oscillations (QBO) with period of 2-2.5 years and even higher period oscillations of 3-4 years are prominent in middle troposphere and lower stratosphere regions which could cause large annual variabilities of OMR fluctuations. Fluctuations of OMR were subjected to Morlet wavelet transform over a year, 2008, to study seasonal variabilities. The wavelet analysis confirm that Madden Julian Oscillations (MJO) with periods 49-60 days are prominent during summer near tropopuase and in lower stratosphere regions, while lower period equatorial Kelvin waves of 14-20 days periods dominate during winter and spring in troposphere region, which could be responsible for maximum seasonal variability.