Stratospheric ozone interannual variability (1995–2011) as observed by lidar and satellite at Mauna Loa Observatory, HI and Table Mountain Facility, CA

Abstract

The Jet Propulsion Laboratory (JPL) lidars, at the Mauna Loa Observatory, Hawaii (MLO, 19.5° N, 155.6° W) and the JPL Table Mountain Facility (TMF, California, 34.5° N, 117.7° W), have been measuring vertical profiles of stratospheric ozone routinely since the early 1990's and late-1980s respectively. Interannual variability of ozone above these two sites was investigated using a multi-linear regression analysis on the deseasonalised monthly mean lidar and satellite time-series at 1 km intervals between 20 and 45 km from January 1995 to April 2011, a period of low volcanic aerosol loading. Explanatory variables representing the 11 yr solar cycle, the El Niño Southern Oscillation, the Quasi-Biennial Oscillation, the Eliassen-Palm flux, and horizontal and vertical transport were used. A new proxy, the mid-latitude Ozone Depleting Gas Index, which shows a decrease with time as an outcome of the Montreal Protocol, was introduced and compared to the more commonly used linear trend method. The analysis also compares the lidar time-series and a merged time-series obtained from the space-borne Stratospheric Aerosol and Gas Experiment II, Halogen Occultation Experiment, and Aura-Microwave Limb Sounder instruments. <br><br> The results from both lidar and satellite measurements are consistent with recent model simulations which propose changes in tropical upwelling. Additionally, at TMF the Ozone Depleting Gas Index explains as much variance as the Quasi-Biennial Oscillation in the upper stratosphere. Over the past 17 yr a diminishing downward trend in ozone was observed before 2000 and a net increase, and sign of ozone recovery, is observed after 2005. Our results which include dynamical proxies suggest possible coupling between horizontal transport and the 11 yr solar cycle response, although a dataset spanning a period longer than one solar cycle is needed to confirm this result

Reconciling differences in stratospheric ozone composites

“…The impact of using SAGE II v6.2 instead of v7.0 is discussed by the GOZCARDS team , which shows very little systematic differences in number density, but leads to large differences when converted to volume mixing ratio (vmr) with temperature from either NCEP or MERRA (as confirmed by Maycock et al, 2016;McLinden et al, 2009). We note that small drifts of ∼ 0.5 % yr −1 do exist between HALOE, SAGE II, and Aura/MLS (Nair et al, 2012;Kirgis et al, 2013), and Nazaryan and McCormick (2005) and Hubert et al (2016) suggest that most of the datasets used in GOZCARDS have good stability.…”

Trend and variability in ozone in the tropical lower stratosphere over 2.5 solar cycles observed by SAGE II and OSIRIS

“…water vapour). Thus, it is not surprising that in the 17.5-23.5 km range, fitting the best pair of pressures considerably improves the r 2 relative to fitting two orthogonalized QBO basis functions derived from all seven pressures, as echoed by Kirgis et al (2013). In fact, in some cases, a single QBO pressure (e.g.…”

“…Here, however, model terms are ultimately dropped at altitudes where they are not statistically significant (defined below). Kirgis et al (2013) also followed a similar approach with different final regression models developed for different ground-based stations. This tailoring of regression models allows the proportion of explained variance to be meaningful.…”

Drift-corrected trends and periodic variations in MIPAS IMK/IAA ozone measurements

“…Others, like Kirgis et al (2013), fit the Ozone Depleting Gas Index (ODGI) instead of a linear term and find that the value of total explained variance is increased compared to using a linear term. However, for the time series used here (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)) the ODGI does not differ noticeably from the linear term, which justifies using a simple linear term here.…”