11:00 AM - 11:15 AM
[PEM13-02] Observations of turbulent layer and ozone vertical distribution in tropical tropopause layer
Keywords:Tropical tropopause layer, Stratosphere-Troposphere Exchange, KH instability
The tropical tropopause layer (TTL) is a transition region between the troposphere and the stratosphere peculiar to the tropical zone. Physical and chemical processes in the TTL are important because they affect Stratosphere-Troposphere Exchange (STE). However, there have been few direct observations of TTL, and most previous researches have focused on large-scale waves, so the details of smaller processes related to TTL and STE are still unknown. In this study, we analyzed small-scale turbulence near the TTL region and the associated transport using the data of observation campaign conducted in collaboration with STRATEOLE-2 (TTL / lower stratospheric observation project using super pressure long duration balloons). Observation campaign was conducted during November 21-December 6, 2019, and we continuously operated the Equatorial Atmosphere Radar (EAR) and launched some ozone and GPS sondes during the campaign.
Figure shows the turbulence intensity calculated from the EAR spectral width data, and the crosses indicate the tropopause defined as the lowest temperature (Cold Point Tropopause; CPT). A turbulent layer that lasted for about 2 days is observed from the evening of December 1. As a result of detailed analysis, the strong zonal wind shear and the west-tilted KH billow due to the distortion of the equatorial Kelvin wave are seen, and the deep convection system affects this, causing multiple fine KH instability and strong turbulence in the altitude range of 1 km. It was also shown that ozone fluctuations are mainly caused by fluctuations in the vertical distribution of temperature due to distortion or breaking of the equatorial Kelvin wave, and that turbulent mixing contributes secondarily.
Statistically, the altitude of the turbulent layer obtained by EAR and the vertical distribution of ozone obtained by Aura-MLS are linked, suggesting that the turbulent layer corresponds to the material boundary. The altitude and intensity of the turbulent layer obtained by the EAR varies depending on the season, and affected by the activity of the equatorial Kelvin wave and convection, and the monsoon. These results suggest that the turbulent layer is caused by equatorial Kelvin wave distortion or breaking and that this wave distortion or breaking fluctuates the distribution of ozone. The turbulent layer observable by EAR with high vertical resolution may be an indicator of such large-scale disturbances.
Figure shows the turbulence intensity calculated from the EAR spectral width data, and the crosses indicate the tropopause defined as the lowest temperature (Cold Point Tropopause; CPT). A turbulent layer that lasted for about 2 days is observed from the evening of December 1. As a result of detailed analysis, the strong zonal wind shear and the west-tilted KH billow due to the distortion of the equatorial Kelvin wave are seen, and the deep convection system affects this, causing multiple fine KH instability and strong turbulence in the altitude range of 1 km. It was also shown that ozone fluctuations are mainly caused by fluctuations in the vertical distribution of temperature due to distortion or breaking of the equatorial Kelvin wave, and that turbulent mixing contributes secondarily.
Statistically, the altitude of the turbulent layer obtained by EAR and the vertical distribution of ozone obtained by Aura-MLS are linked, suggesting that the turbulent layer corresponds to the material boundary. The altitude and intensity of the turbulent layer obtained by the EAR varies depending on the season, and affected by the activity of the equatorial Kelvin wave and convection, and the monsoon. These results suggest that the turbulent layer is caused by equatorial Kelvin wave distortion or breaking and that this wave distortion or breaking fluctuates the distribution of ozone. The turbulent layer observable by EAR with high vertical resolution may be an indicator of such large-scale disturbances.