|
|
 |
|
|
Ann. Geophys., 21, 2095-2106, 2003
www.ann-geophys.net/21/2095/2003/
© European Geosciences Union 2003
Investigation of the short-time variability of tropical tropospheric ozone
T. Randriambelo1, J.-L. Baray1, S. Baldy1, A. M. Thompson2, S. Oltmans3, and P. Keckhut4
1Laboratoire de Physique de l’Atmosphere, UMR-CNRS 8105,15 Avenue René Cassin, Reunion Island 97715, France
2NASA Goddard Laboratory for Atmosphere, GSFC, Greenbelt, MD, USA
3NOAA, Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado, 325 Broadway, Boulder, Colorado, USA
4Service d’Aeronomie, BP 3, 91371 Verriéres-le-Buisson Cedex Paris, France
Abstract. Since 1998, a
ground-based tropospheric ozone lidar has been running at Reunion Island and
has been involved with a daily measurement campaign that was performed in the
latter part of the biomass burning season, during November–December 1999. The
averaged ozone profile obtained during November–December 1999 agrees well
with the averaged ozone profile obtained from the ozonesondes launch at Reunion
during November–December (1992– 2001). Comparing weekly sonde launches
(part of the Southern Hemisphere Additional Ozonesondes: SHADOZ program) with
the daily ground-based lidar observations shows that some striking features of
the day-to-day variability profiles are not observed in the sonde measurements.
Ozone profiles respond to the nature of disturbances which vary from one day to
the next. The vertical ozone distribution at Reunion is examined as a function
of prevailing atmospheric circulation. Back trajectories show that most of the
enhanced ozone crossed over biomass burning and convectively active regions in
Madagascar and the southern African continent. The analyses of the
meteorological data show that ozone stratification profiles are in agreement
with the movement of the synoptic situations in November–December 1999. Three
different sequences of transport are explained using wind fields. The first
sequence from 23 to 25 November is characterized by northerly transport; during
the second sequence from 26 to 30 November, the air masses are influenced by
meridional transport. The third sequence from 2 to 6 December is characterized
by westerly transport associated with the sub-tropical jet stream. The large,
standard deviations of lidar profiles in the middle and upper troposphere are
in agreement with the upper wind variabilities which evidence passing ridge and
trough disturbances. During the transition period between the dry season and
the wet season, multiple ozone sources including stratosphere-troposphere
exchanges, convection and biomass burning contribute to tropospheric ozone at
Reunion Island through sporadic events characterized by a large spatial and
temporal variability.
Key words. Atmospheric composition
and structure (troposphere-composition and chemistry) – Meteorology and
atmospheric dynamics (climatology; tropical meteorology)
Full Article in PDF (1699 KB) |
|
|
