Tropospheric ozone profiles by DIAL at Maïdo Observatory (Reunion Island): system description, instrumental performance and result comparison with ozone external data set
In order to recognize the importance of ozone (O<sub>3</sub>) in the troposphere and lower stratosphere in the tropics, a DIAL (differential absorption lidar) tropospheric O<sub>3</sub> lidar system (LIO3T<sub>UR</sub>) was developed and installed at the Univer...
| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-09-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/10/3359/2017/amt-10-3359-2017.pdf |
| Summary: | In order to recognize the importance of ozone (O<sub>3</sub>) in the troposphere
and lower stratosphere in the tropics, a DIAL (differential absorption lidar)
tropospheric O<sub>3</sub> lidar system (LIO3T<sub>UR</sub>) was developed and
installed at the Université de la Réunion campus site (close to the
sea) on Reunion Island (southern tropics) in 1998. From 1998 to 2010, it
acquired 427 O<sub>3</sub> profiles from the low to the upper troposphere and has
been central to several studies. In 2012, the system was moved up to the new
Maïdo Observatory facility (2160 m a.m.s.l. – metres above mean sea
level) where it started operation in February 2013. The current system
(LIO3T) configuration generates a 266 nm beam obtained with the fourth
harmonic of a Nd:YAG laser sent into a Raman cell filled up with deuterium
(using helium as buffer gas), generating the 289 and 316 nm beams to enable
the use of the DIAL method for O<sub>3</sub> profile measurements. The optimal
range for the actual system is 6–19 km a.m.s.l., depending on the
instrumental and atmospheric conditions. For a 1 h integration time,
vertical resolution varies from 0.7 km at 6 km a.m.s.l. to 1.3 km at
19 km a.m.s.l., and mean uncertainty within the 6–19 km range is between
6 and 13 %. Comparisons with eight electrochemical concentration cell
(ECC) sondes simultaneously launched from the Maïdo Observatory show good
agreement between data sets with a 6.8 % mean absolute relative
difference (<i>D</i>) between 6 and 17 km a.m.s.l. (LIO3T lower than ECC).
Comparisons with 37 ECC sondes launched from the nearby Gillot site during
the daytime in a ±24 h window around lidar shooting result in a
9.4 % <i>D</i> between 6 and 19 km a.m.s.l. (LIO3T lower than ECC).
Comparisons with 11 ground-based Network for Detection of Atmospheric
Composition Change (NDACC) Fourier transform infrared (FTIR) spectrometer
measurements acquired during the daytime in a ±24 h window around lidar
shooting show good agreement between data sets with a <i>D</i> of 11.8 % for
the 8.5–16 km partial column (LIO3T higher than FTIR), and comparisons with
39 simultaneous Infrared Atmospheric Sounding Interferometer (IASI)
observations over Reunion Island show good agreement between data sets with a
<i>D</i> of 11.3 % for the 6–16 km partial column (LIO3T higher than IASI).
ECC, LIO3T<sub>UR</sub> and LIO3T O<sub>3</sub> monthly climatologies all exhibit
the same range of values and patterns. In particular, the Southern Hemisphere
biomass burning seasonal enhancement and the ozonopause altitude decrease in
late austral winter–spring, as well as the sign of deep convection bringing
boundary layer O<sub>3</sub>-poor air masses up to the middle–upper troposphere in
late austral summer, are clearly visible in all data sets. |
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| ISSN: | 1867-1381 1867-8548 |