1. Seasonal Differences of UTLS Exchange Processes between Spring and Summer in the Subtropics and Polar Region
Simone Tilmes, Laura Pan,
Louisa Emmons, Hans Schlager,
START08 team, ARCTAS team, GRACE team
UTLS Workshop, October19-22, 2009

2. Overview Aircraft data used (O3 and CO)
Method to divide the Extra-Tropics into Sub-Tropics and Polar Region
Differences in Tracer Characteristics
Differences in Exchange/Mixing Processes using
Tracer-Tracer Correlations
Connection between the stability of the atmosphere and exchange characteristics in the polar region
We use aircraft data from 4 campaigns with most of them taken place in 2008, to contrast tracer characteristics and of O3 and CO between two region, the sub-tropics and the extra tropics and for spring and summer

3. Aircraft Data
STRAT-POLARIS; START08; POLARCAT: ARCTAS/ GRACE, April to July 2008
We use aircraft data from 4 campaigns, which cover two seasons and mid and high latitudes in spring and summer. We used mostly data from campaigns in 2008 but add STRAT/POLARIS to cover high latitudes especially in Polar regions. STRAT08 covers mostly the latitudes between degreesN Arctas: > 60N and
POLar study using Aircraft Remote sensing, surface measurements and modelsof Climate, chemistry, Aerosols, and Transport (PO- LARCAT) for the polar year
Altitude (km)
Latitude

4. Definition of Regions based on the Tropopause Height
dΦ/dz (K/km) EQ EQ
Pol
Pol

5. Definition of Regions based on the Tropopause Height
dΦ/dz (K/km)
Sub-Tropics
Sub-Tropics
Polar-
Region
Polar-
Region
Tropics
Tropics EQ EQ
Pol
Pol
Tropics: TP > 365 K pot. Temp.
Subtropics: 325 K < TP < 365 K, Winter/Spring
335 K < TP < 365 K, Summer/Fall
plus: double TP events
Polar Region: TP > 325 K, Winter/Spring
TP > 335 K, Summer/Fall
Sub-Tropics: Region influence by
frequent exchange with the Tropics
Polar Region: Region influenced by
exchange across the local Tropopause

6. Tracer Characteristics in Subtropics and the Polar Region
Spring
Summer

7. Relative Altitude /Ozone
Subtropics
Polar Region
Spring
Point to the amount of sampling
Summer
Subtropics: Bi-model distribution in 0-4km above the Tropopause
wider distribution in Spring than in summer
Polar Region: distribution is more compact especially in spring compared
to the Subtropics

8. Relative Altitude /CO Subtropics Polar Region Spring Summer
Subtropics: Bi-model distribution in 0-4km above the Tropopause
larger surface values in Spring than in summer
Polar Region: influence of convection and long-range transport

9. O3/CO Correlations Subtropics Polar Region Spring Summer
Region of mixing identified using tracer-tracer correlations
Stratospheric branch: fit of profiles O3 > 600 ppbv and CO < 35ppbv
Tropospheric branch: fit of profiles < 100 ppbv

10. dΦ/dz (K/km) Different Regions of Mixing above 365 K
above the TP; below 365 K
below the TP EQ
Pol
Subtropics
dΦ/dz (K/km)
O3 (ppbv)
CO (ppbv)

11. Different Regions of Mixing above 365 K above the TP; below 365 K
below the TP
Subtropics
With the purpose to separate mixing that is introduced by horizontal exchange with the Tropical TP and mixing with the LMS.
O3 (ppbv)
CO (ppbv)

12. Mixed data
above 365 K
above the TP; below 365 K
below the TP
Subtropics
O3 (ppbv)
CO (ppbv)

13. Mixed data
above 365 K
above the TP; below 365 K
below the TP
Subtropics
O3 (ppbv)
CO (ppbv)

14. Mixed data
above 365 K
above the TP; below 365 K
below the TP
Subtropics
Ozone CO
Spring
Summer

15. Mixed data
above 365 K
above the TP; below 365 K
below the TP
Subtropics
Ozone CO
Fraction of samples
Relative Altitude (km)

16. Mixed data
above 365 K
above the TP; below 365 K
below the TP
Polar Region

17. Mixed data
above 365 K
above the TP; below 365 K
below the TP
Polar Region
Spring
Summer

18. Mixed data
above 365 K
above the TP; below 365 K
below the TP
Polar Region
Fraction of samples
convection
Relative Altitude (km)
Schlager et al., in preparation

19. Transition Region in Spring, Polar Region
Mixed data
above 365 K
above the TP; below 365 K
below the TP
Fraction of samples
Can we understand the with
of the transition region and the
distribution?
Relative Altitude (km)

20. Case Study: ARCTAS April 09, 2008
dΦ/dz (K/km)
Correlation between static stability and tracer gradients across the TP another example as yesterday shown for Mozaic..

21. Case Study: ARCTAS April 09, 2008
dΦ/dz (K/km)
Connection to the meteorological conditions
We need to explore the frequency of enhanced/reduced static stability
below/above the TP to quantify the location of thickness of the transition layer

22. Summary: Depth of the transition layer
Mixed data
above 365 K
above the TP;
below 365 K
below the TP
Fraction of samples
Sub-tropics: very large contribution of mixing in altitudes above 365.K
Polar region: Aircraft data show a larger contribution of mixing above the TP in spring. Example shows that observations did sample more cases where static stability shows a strong gradient across the TP.
Relative Altitude (km)

23. Conclusions Results show:
characteristic tracer behavior in each region
seasonal and regional differences in exchange processes and width of the tropopause
seasonal differences are less pronounced
extended climatology is used within the CCMVAl diagnostics
Further work:
an extended set of aircraft observations is desired, especially for the polar regions to support these results
model data will be used in future studies to elaborate the representativeness of a limited set of aircraft data used