Comparison of Long Term Tropospheric Ozone Trends Measured by Lidar and ECC Ozonesondes from 1991 to 2010 in Southern France

G Ancellet,S Godin-Beekmann,A Gaudel,B Gross,M Arend,F Moshary

doi:10.1051/epjconf/201611920002

Abstract

ECC (Electrochemical Concentration Cell) ozonesondes and UV DIAL (Differential Absorption Lidar) measurements have been carried out simultaneously at OHP (Observatoire de Haute Provence, 44°N, 6.7°E, 690 m) since 1991. A unique long-term trend assessment by two different instruments operated routinely at the same location is possible. Air mass trajectories have been calculated for all the ozone observations available at OHP. The bias between the seasonal mean calculated with lidar and ECC ozone vertical profiles for 4 timeperiods of 5 years is 0.6 ppbv in the free troposphere (4-8 km). Larger differences (> 10 ppbv) are explained by the need for clear sky conditions during lidar observations. The measurements of both instruments have been combined to decrease the impact of short-term atmospheric variability on the trend estimate.

Highlights

Considering the spatial and temporal variations of the tropospheric ozone trend calculated in Northern and central Europe [1], analysis of ozone vertical profiles in Southern Europe is missing
It is a bit surprising that lidar with more observations indicates larger interannual variability. It may only be explained by some inter-annual variability of the meteorological conditions necessary for the lidar observations
The comparison conducted using this long time series reveals a bias between both measurement types (ECC - lidar) of the order of 0.6 ppbv

Summary

Introduction

Considering the spatial and temporal variations of the tropospheric ozone trend calculated in Northern and central Europe [1], analysis of ozone vertical profiles in Southern Europe is missing. Regular lidar and ECC (Electrochemical Concentration Cell) ozonesondes are available since 1991 and can be used for a long-term trend analysis at OHP (Observatoire de Haute Provence, 44°N, 6.7°E, 690 m)). OHP is a good station to characterize the Mediterranean basin where there is a significant spatial positive anomaly of tropospheric ozone, especially during summer.

Methods

Results

Conclusion