Equatorial stratospheric thermal structure and ozone variations during the sudden stratospheric warming of 2013

Abstract

Ozone mass mixing ratio (OMMR) obtained from both European Centre for Medium Range Weather Forecasting (ECMWF) Reanalysis (ERA)-Interim and Sounding of Atmosphere by Broadband Emission Radiometry (SABER) instrument onboard Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite shows large values in the equatorial upper stratosphere during the occurrence of a major stratospheric sudden warming (SSW) in January 2013 preceded by a large reduction of planetary wave activity. However, surprisingly equatorial stratospheric temperature is found to decrease at pressure levels where the ozone mixing ratio is larger. The computed radiative heating rate using Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model also shows positive heating rate indicating that the temperature should increase in response to the ozone accumulation over equator. In addition to radiative heating due to ozone, heating rate due to other dominant factors, namely, ascending motion and convergence of meridional heat flux, which could influence the thermal structure of the equatorial stratosphere, are estimated. It is found that the observed low temperature during SSW is mainly due to large upward motions. The estimated heating rates agree reasonably well with the observed heating rates at 10-8hPa indicating the dominance of transport at lower stratosphere. The large discrepancy between the estimated and observed heating rates in the upper stratosphere may be due to the dominance of photochemistry.