Abstract
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. 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.
Highlights
Methods andThe concentration and disDtribauttaionSoyfsstteramtosspheric ozone is from January 1995 to April 2011, a period of low volcanic determined by three processes: in situ creation, aerosol loading
Due to the low number of HALOE and SAGE II coincidences, it was found that relaxing time coincidences and using every profile available in a month over each site leads to lower biases between merged-satellite and lidar time series and better correlation coefficients between the regression model results
This study presented a multi-linear regression analysis using ∼ 17 yr of stratospheric ozone measurements by lidar and satellite-borne instruments above Table Mountain, California and Mauna Loa, Hawaii (20 to 40 km)
Summary
The concentration and disDtribauttaionSoyfsstteramtosspheric ozone is from January 1995 to April 2011, a period of low volcanic determined by three processes: in situ creation (production), aerosol loading. The averaged differences between the merged HALOE+SAGE II values and the MLS values over the overlapping period June 2004–May 2005 were used to correct the MLS measurements from 2005 to 2011 For both lidar and merged-satellite datasets, ozone mixing ratio monthly means were calculated and deseasonalised by subtracting the climatological mean for each month from January 1995 to April 2011. Due to the low number of HALOE and SAGE II coincidences, it was found that relaxing time coincidences and using every profile available in a month over each site leads to lower biases between merged-satellite and lidar time series and better correlation coefficients (usually up to 18–19 %) between the regression model results. Region at 25 km which explains the better agreement in the results than at TMF where ozone anomalies values are much higher
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