EGU2020-937
https://doi.org/10.5194/egusphere-egu2020-937
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The stratospheric ozone rich cold intrusion during El-Nino over the Indian region: implication during the Indian summer monsoon

Chaitri Roy1,2, Suvarna Fadnavis1, and Sabin Thazhe Purayil1
Chaitri Roy et al.
  • 1Centre for Climate Change Research, Indian Institute of Tropical Meteorology, Pune, India (chaitri.roy@gmail.com)
  • 2Department of Atmospheric and Space Sciences, Savitribai Phule Pune University, Pune, India (chaitri.roy@gmail.com)

Ozone in the upper troposphere is a dominant radiative constituent.  In this study, we investigate ozone variability due to stratospheric intrusions in the upper troposphere over India, and its associated radiative impacts during monsoon breaks co-occurring with El Niño. For this purpose, we use the ECHAM5-HAMMOZ, Global-Chemistry-climate model simulations, and ERA-Interim reanalysis data. Our analysis shows that during El Niño deep stratospheric intrusions, occurring at the North India - Tibetan Plateau (NI-TP) region and the western edge of the monsoon anticyclone, lead to an enormous increase in ozone amounts (~160 ppb) in the upper troposphere over India. These intrusions elevate the surface ozone levels by ~20 ppb and ozone radiative forcing by ~0.33 W m-2 at the top of the atmosphere (TOA). 

Interestingly, the stratospheric intrusions are associated with a wave train composed of cyclonic and anticyclonic circulation in the upper troposphere, emanating from El-Niño region in the east Pacific, traversing towards NI-TP locale. The wave train transports extra-tropical cold air mass, producing an anomalous cooling of ~2 - 3 K in the upper troposphere over NI-TP. The cold wave train induces Rossby wave breaking (RWB), which facilitates stratospheric intrusions, thereby enhancing subsidence over NI-TP region. Additionally, this severe cold subsidence over North India during break days may further intensify the deficit rainfall condition during break days.

How to cite: Roy, C., Fadnavis, S., and Thazhe Purayil, S.: The stratospheric ozone rich cold intrusion during El-Nino over the Indian region: implication during the Indian summer monsoon, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-937, https://doi.org/10.5194/egusphere-egu2020-937, 2019

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