1. Latmos UPMC/CNRS - ILRC 2015
long term tropospheric ozone trends measured by lidar and ECC ozonesondes from 1991 to 2015 in Southern France G. Ancellet, A. Gaudel, S. Godin-Beekmann
ECC
LIDAR
OHP NDACC
Station 44N, 6E
700 m asl
Surface ozone monitor
Latmos UPMC/CNRS - ILRC 2015

2. OHP tropospheric ozone lidar
Transmitter: Nd:YAG + SRS in D2
20 Hz, 10 mJ at 289 and 316 nm (266 nm not used)
Receiver: 80 cm telescope diameter
Grating spectrometer
LICEL data acquisition system (analog + photocounting)
Measurement altitude: km asl ( )
3-15 km asl ( )
km asl (2012-today)
Integration time ≈ 1 hour (sunset)
2 profiles per week on average
O3 concentration accuracy (intercomparison campaigns with balloon and aircraft) ≤ 7 %
Data removed in cloud or thick aerosol layers
Overlap function correction in the 2-4 km range.
Major changes:
- March 1993: switch from 2 Raman cells (289/299 nm) to one (289/316 nm)
- March 2012: switch to LICEL data acquisition, more stable optical design between laser and telescope
Latmos UPMC/CNRS – LWG 2016

3. Ozone profile vertical/temporal averaging for the study of the interannual variability
Lidar
ECC
NAO
Pinatubo
2003
1991
1995
1996
2000
2001
2005
2006
2010
2011
2015
611 profiles
593 profiles
445 profiles
504 profiles
539 profiles
Lidar
390 profiles
337 profiles
232 profiles
260 profiles
290profiles
ECC
221 profiles
256 profiles
213profiles
244 profiles
249 profiles
Surface O3
Latmos UPMC/CNRS -LWG 2016

4. Air mass transport assessment and PTU vertical profiles at OHP
ERA interim ECMWF analysis 1° resolution 60 vertical levels:
Temperature, humidity, PV vertical profiles from 0 to 20 km for each lidar and ECC profiles
Flextra 4 days backward trajectories: 700 hPa, 500 hPa, 400 hPa, Tropopause Layer (2km below PV=1.5)
Arctic
Europe
America
Asia

5. Comparison of 5-year O3 seasonal averages
Less southerly
flow for lidar
than for ECC in
Period
small transport
differences
Good proxy for
ECC –lidar bias
≤-1 ppb
Latmos UPMC/CNRS – LWG 2016

6. Trend above 6km are significant
Trends - Global
According to IPCC method trends are defined as
Virtually certain: pvalue < 0.01
Very likely: pvalue < 0.1
Likely: pvalue < 0.34
About as likely as not: pvalue =
Unlikely: pvalue > 0.67
Very unlikely: pvalue > 0.90
Exceptionally unlikely: pvalue > 0.99
Trend above 6km are significant
Decrease only at the surface for which there is ECC data only

7. Trends per region
Number of data is reported on the figure for each year
For Europe:
- Trends are quite similar to the global trends
For America:
- Likely trend at 2-4km and higher than global
- Not likely trends at 4-6km and close to the surface and trends values are lower than global

8. Trends per region
Number of data is reported on the figure for each year
Fore Arctic and Asia, very low sampling, not sure we can use it…

9. Trends per PV range
Number of data is reported on the figure for each year
For PV < 0.75 Pvu or PV > 0.75PVu trends quite similar to the global trends,
Except for UT for which trend’s value is lower than for global (0.24ppbv/yr instead of 0.37ppbv/yr)

10. Conclusions
24-year regular tropospheric O3 measurements with two different instruments (ECC and lidar)
Meteorological bias for lidar measurements and instrumental bias between ECC and lidar less than -1 ppbv for 5-year seasonal averages in the free troposphere (consistent with lidar accuracy during intercomparison campaign < 7%)
Need to use both ECC and lidar measurements to improve the interannual variability analysis
No O3 trend in the mid troposphere while there is a significant positive trend (3 ppbv/decade) below the tropopause
At 700 hPa variable trend probably linked to NAO and large transport
Decrease in the PBL (-1.4 ppbv/decade) consistent with ground-based ozone trend in Southern Europe
Latmos UPMC/CNRS - LWG 2016

11. Latmos UPMC/CNRS - ILRC 2015
Perspectives
Projet Tropospheric Ozone Assessment Report (TOAR) dans cadre IGAC: rendu en 2017
Réseau lidar troposphérique TOLNET aux USA associant NASA, NOAA, NCAR (coordination M. Newchurch, Huntsville)
Activité de Ozone sonde expert group pour harmonization longues series de mesure: mise à jour des 1171 sondes OHP avec tous les paramètres permettant ce travail (merci à Nathalie Poulet !)
Latmos UPMC/CNRS - ILRC 2015