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

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

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 30-60 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

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

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

Tracer Characteristics in Subtropics and the Polar Region Spring Summer

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

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

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

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)

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)

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

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

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

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

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

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

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

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)

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..

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

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)

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