Keywords:COSMIC, GPS-RO, Full Spectrum Inversion, Tropopause Inversion Layer
This study focuses on the sharp variations of the temperature structure near the cold point tropopause (CPT), which is called the tropopause inversion layer (TIL). We analyze the height variations of the Brunt-Väisälä frequency squared (N2) from the vertical gradient of the temperature data retrieved from the COSMIC GPS-RO in 2007-2016 using the Full Spectrum Inversion (cosmicfsi), which has the vertical resolution of about 0.1 km. This study describes new definition of tropical TIL utilizing high resolution of cosmicfsi that able to delineate the thin layer of static stability near tropopause. We examine the statistical distribution of the TIL parameters; such as S-aCPT, which is the difference between the maximum N2 above CPT (maxN2) and N2 at CPT, and S-bCPT, the difference between the minimum N2 below CPT (minN2) and N2 at CPT, the height difference distance for maxN2 and minN2 relative to CPT (dH-aCPT and dH-bCPT). The mean values of S-aCPT and S-bCPT are 6.2 × 10−4 s−2 and 4.0 × 10−4 s−2, respectively, and the standard deviation of S-aCPT is approximately three times larger than that for S-bCPT. The mean and standard deviation of both dH-aCPT and dH-bCPT are 0.4 ± 0.2 km and 0.5 ± 0.2 km, respectively. We find S-aCPT reached up to > 10 × 10−4 s−2 from its random frequency distribution and dH-aCPT was mostly < 0.5 km, indicating a very sharp thermal gradient due to very low temperature. We also discuss the TIL depth (dH) which is defined as height difference at N2 equal to 80% of maxN2.