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Dynamical Influence on Inter-annual and Decadal Ozone Change
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Sandip Dhomse, Mark Weber, J.P.
Burrows
Universtät Bremen FB1, Institüt für
Umweltphysik (iup)
Outline
• Introduction• Data used• Inter-annual variability• Decadal variability• Tele-connection patterns
(Introduction)• Summary and Conclusion• Outlook
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No abrupt change in chemical composition
Introduction
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Sun - at the same position
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Total Ozone is higher in NH (spring) than SH (spring)
Low TOZ
In tropics
Relatively High TOZ in tropics during SH spring
Wave activity controls
• Stratospheric
circulation
• Stratosphere
Troposphere
Exchange
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Holton et al., 1995
SH winter- colder
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Mean Winter temp. (shaded) And zonal wind (contour) for NH and SH
SH – polar jet stronger
Tropopause colder during NH winter
Planetary waves
Planetary waves are large-scale distortions to the mean flow
The flow (black) meanders across latitude circles (blue).
V
V
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Brewer-Dobson circulation
•Breaking planetary waves apply a FORCE to the winds-
decelerates the speed
•Pressure gradient force- remains unaffected
•Corioli’s force - REDUCED so there is a net force towards the
pole.
•Air RISES over the equator, drifts steadily POLEWARD
(while meandering around the latitude circles) and SINKS at
the poles
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Two components of EP flux are calculated as,(Andrews,et.al 1987)
)''/'']/)cos()cos({[cos
)''/''(cos
10
)(
0)(
uwvuuafaF
uvvuaF
zzz
zz
And its divergence is
z
FFaF
z
)cos()cos( 1
• Eliassen Palm (EP) flux vector is a measure of the upward propagating momentum carried by planetary waves
• The divergence of EP flux gives the volume where momentum is deposited
Measuring the wave activity
Heat flux
Momentum flux
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Measuring the wave activity
)))(((''
)))(((''
TTvvmeanTv
vvuumeanvu
zonalzonal
zonalzonal
''vuF
''TvF z
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Data used
Meteorological data set • ERA40 - 23 pressure levels• ERA15 - 17 pressure levels• UK Met. Office - 22 pressure levels • ECMWF - 21 pressure levels• NCEP - 17 pressure levels
Ozone data set• GOME - total ozone data • TOMS - total ozone data
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Inter-annual variation of flux and Ozone
High flux - increase in Brewer-Dobson circulation - more transport
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Record high lower stratosphericheat flux on 20th/21stSeptember (ERA40 1960-2002)
Splitting of the polar vortex on 26th September 2002
First major stratospheric warming in SH
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wave activity and winter gain in ozone
Weber et al. 2003
High correlation between winter heat flux (wave activity) and spring/fall ozone ratio
Winter ozone gain in Antarctic 2002 presents an intermediate case between other Antarctic winters and cold Arctic winters (higher contribution from transport)
High Heat flux –Low PSC
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Does dynamics the same? Or Chemistry is changing?
Model Differences
ERA40
ERA40 +ERA15
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Northern Hemisphere
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SH – pre-satellite period – Problem?
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PSC volume using ERA40 data
T <195 K (PSC volume)
SH (JAN-DEC)NH (JUL-JUN)
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Days (Jul-Jun)
195 K- PSC temperature
SH –colder temperature
Days (Jan-Dec)
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No significant trend in heat flux
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Different models – different trends
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No significant trend in any dataset in heat flux as well as EP Flux
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Summary
• Strong correlation between seasonal heat flux and total ozone in March.
• No significant trend on seasonal scale in heat flux.
• Maximum cooling trend is in November and January ( -1.2 K/decade) , but there is not trend in heat flux.
• Different models, different periods lead to different trends.
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Bremen- 10/23/2003
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Arctic Oscillation
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Conclusion
• There are no significant trends in 2D (latitude & altitude) analysis of the data.
• 3D analysis of data will be useful to find the dependence of ozone on different tele-connection patterns.
• EOF analysis is good tool for 3D analysis.
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Outlook
• Study ozone dependence on different tele-connection pattern using EOF technique.
• Find out different patterns in the ozone variability using GOME vertical profile data (neural network) , TOMS, SAGE, POAM, ozonesonde datasets.
Thank you very much for your kind attention!!!
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