Long-term variabilities and tendencies in zonal mean TIMED–SABER ozone and temperature in the middle atmosphere at 10–15°N

Abstract

Long-term variabilities and trends of middle atmospheric (20–100km) ozone volume mixing ratio (OVMR) and temperature and their responses towards quasi-biennial oscillation (QBO), solar cycle (SC) and El Niño-southern oscillation (ENSO) have been investigated using monthly averaged zonal mean Sounding of Atmosphere by Broadband Emission Radiometry (SABER) observations at 10–15°N for the years 2002–2012. Composite monthly mean of OVMR shows semi-annual oscillation (SAO) predominantly in the lower stratosphere (20–30km) and in the upper mesosphere (above 90km), whereas that of temperature shows SAO in the upper stratosphere (45–55km) and lower mesosphere (60–75km). Amplitudes of SAO and annual oscillation (AO) in OVMR show enhancement above 80km and 90km respectively in the mesosphere and both show maximum around 30km in the stratosphere. The amplitudes of SAO and AO in temperature show maxima just below and above 80km in the mesosphere, whereas in the stratosphere, they show maxima around 40km and 20km respectively. The phase profiles of SAO and AO in temperature show downward progressions below 80km, whereas the phase profile of SAO in OVMR shows downward progression only below 40km and the phase remains constant above 80km. Regression analysis of OVMR shows increasing trend at 23km, and small decreasing trend at 30km, 34km and above 80km. Above 92km, the trend sharply decreases. OVMR response to QBO winds at 30hPa shows negative maxima at 30km and 91km, positive maximum at 26km and is insignificant at other heights. The OVMR response to SC is positive in the middle stratosphere peaking at 31km and in the upper mesosphere peaking at 95km. The OVMR response to ENSO shows mixed behavior in stratosphere and positive in the upper mesosphere. It is positive in the lower height region 20–27km with maximum at 25km. The response to ENSO is insignificant up to 70km and it is positive above 80km with two maxima at 87km and 97km. Regression analysis of temperature shows cooling trends in most of the stratosphere and the mesosphere (40–90km). The temperature response to SC is increasingly positive above 40km. The temperature response to ENSO is negative in the middle stratosphere and positive in the lower and upper stratosphere. In mesosphere, it is largely negative in the height range 60–80km and positive above 80km.