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Volume 16, issue 13
Atmos. Chem. Phys., 16, 8581–8591, 2016
https://doi.org/10.5194/acp-16-8581-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 16, 8581–8591, 2016
https://doi.org/10.5194/acp-16-8581-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 15 Jul 2016

Research article | 15 Jul 2016

Effect of tropical cyclones on the stratosphere–troposphere exchange observed using satellite observations over the north Indian Ocean

M. Venkat Ratnam1, S. Ravindra Babu2, S. S. Das3, G. Basha1, B. V. Krishnamurthy4, and B. Venkateswararao2 M. Venkat Ratnam et al.
  • 1National Atmospheric Research Laboratory (NARL), Gadanki, India
  • 2Centre for Earth, Atmosphere and Weather Modification Technologies (CEA&WMT), Jawaharlal Nehru Technological University, Hyderabad, India
  • 3Space Physics Laboratory (SPL), VSSC, Trivandrum, India
  • 4CEBROSS, Chennai, India

Abstract. Tropical cyclones play an important role in modifying the tropopause structure and dynamics as well as stratosphere–troposphere exchange (STE) processes in the upper troposphere and lower stratosphere (UTLS) region. In the present study, the impact of cyclones that occurred over the north Indian Ocean during 2007–2013 on the STE processes is quantified using satellite observations. Tropopause characteristics during cyclones are obtained from the Global Positioning System (GPS) radio occultation (RO) measurements, and ozone and water vapour concentrations in the UTLS region are obtained from Aura Microwave Limb Sounder (MLS) satellite observations. The effect of cyclones on the tropopause parameters is observed to be more prominent within 500 km of the centre of the tropical cyclone. In our earlier study, we observed a decrease (increase) in the tropopause altitude (temperature) up to 0.6 km (3 K), and the convective outflow level increased up to 2 km. This change leads to a total increase in the tropical tropopause layer (TTL) thickness of 3 km within 500 km of the centre of cyclone. Interestingly, an enhancement in the ozone mixing ratio in the upper troposphere is clearly noticed within 500 km from the cyclone centre, whereas the enhancement in the water vapour in the lower stratosphere is more significant on the south-east side, extending from 500 to 1000 km away from the cyclone centre. The cross-tropopause mass flux for different intensities of cyclones is estimated and it is found that the mean flux from the stratosphere to the troposphere for cyclonic storms is 0.05 ± 0.29 × 10−3 kg m−2, and for very severe cyclonic storms it is 0.5 ± 1.07 × 10−3 kg m−2. More downward flux is noticed on the north-west and south-west side of the cyclone centre. These results indicate that the cyclones have significant impact in effecting the tropopause structure, ozone and water vapour budget, and consequentially the STE in the UTLS region.

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Short summary
The impact of cyclones that occurred over the north Indian Ocean during 2007–2013 on the STE process is quantified using satellite observations. It is shown that cyclones have a significant impact on the tropopause structure, ozone and water vapour budget, and consequentially STE in the UTLS region. The cross-tropopause mass flux from the stratosphere to the troposphere for cyclonic storms is found to be 0.05 ± 0.29 × 10−3 kg m−2, and for very severe cyclonic storms it is 0.5 ± 1.07 × 10−3 kg m−2.
The impact of cyclones that occurred over the north Indian Ocean during 2007–2013 on the STE...
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