Impact of quasi-biennial oscillation on the inter-annual variability of the tropopause height and temperature in the tropics: A study using COSMIC/FORMOSAT-3 observations

The effect of quasi-biennial oscillation (QBO) on the temperature of cold point tropopause (T-CPT) and its height (H-CPT) is being investigated using radio occultation measurements by COSMIC/FORMOSAT-3. Observations comprising of 935,863 numbers of occultations have been used to study the zonal mean seasonal variability in T-CPT and H-CPT from January 2007 to December 2011. Results are shown over 30°N–30°S geographic latitudes. In general, T-CPT is found to be the coldest in February and the warmest in August. H-CPT attains maximum height during December–February and minimum during July–August. Interestingly, H-CPT shows maxima at off-equator region (around 20°N or 20°S) during all the seasons in both hemispheres. H-CPT at off-equatorial region, in reference to the equatorial region, is slightly higher (~ 1.0 km) during winter as compared to monsoon season (~ 0.5 km) in Northern Hemisphere (NH). Inter-annual variation in T-CPT and H-CPT found to be clearly influenced by the QBO. Westerly (easterly) phase generates warm (cold) T-CPT, which consequently results a decrease (increase) in H-CPT. It is concluded that QBO induces the changes in T-CPT by as much as 2 °C and in H-CPT by 0.5 km.