1. Influence of the Brewer-Dobson Circulation on the Middle/Upper Tropospheric O 3 Abstract Lower Stratosphere --------Observations-----------------------------Models--------------------- Middle Troposphere TES is used in the mid-upper troposphere to compare with models. Anomalous enrichments are simulated in the MOZART-2-NCEP during winter/spring seasons at mid-high latitudes. Between models, STE ozone fluxes vary by a factor of four (340-1440 Tg/yr; Wild O., 2007). O3 ppbv The phase of seasonal cycle between models and observations is good in the lower stratosphere. A few-month lag is observed at mid-troposphere in the spring/summer seasons. MLS TES MOZART-2-NCEP MOZART-2-MACCM3CAM MOZART-2 using reanalysis data of NCEP MOZART-2-NCEP without surface emission and lightning MOZART-2-NCEP without surface emissions of NO x and mechanism of lightning is simulated (center picture). Lightning is an important source of NO x or O 3 at low latitudes. In MOZART-2-NCEP, the total contribution of lightning is ~5 Tg/yr. Percentage difference of the above results (~contribution from surface emissions and lightning) TES maximum Latitude References: Horowitz, L. W., et al. (2003), A global simulation of tropospheric ozone and related tracers: Description and evaluation of MOZART, version2, J. Geophys. Res., 108(D24), 4784, doi:10.1029/2002JD002853. Logan, Jennifer A. (1999), An analysis of ozonesonde data for the troposphere: Recommendations for testing 3-D models and development of a gridded climatology for tropospheric ozone, J. Geophys. Res., 104 (D13), 16,115-16,149. Shia, R.L., M. C. Liang, C. Miller, and Yuk L. Yung (2006), CO 2 in the upper troposphere: Influence of stratosphere-troposphere exchange, Geophys. Res. Lett., 33, L14814, doi:10.1029/2006GL026141. Wild O. (2007), Modelling the global tropospheric ozone budget: exploring the variability in current models, Atmos. Chem. Phys., 7, 2,643-2,660. Worden, H. M., et al. (2007), Comparisons of Tropospheric Emission Spectrometer (TES) ozone profiles to ozonesondes: Methods and initial results, J. Geophys. Res., 112, D03309, doi:10.1029/2006JD007258. Wu, Shiliang, et al., (2007), Why are there large differences between models in global budgets of tropospheric ozone?, J. Geophys. Res., 112, D05302, doi:10.1029/2006JD007801. TES and MLS data are used to study tropospheric ozone from the middle troposphere to the lower stratosphere. In both hemispheres, MOZART-2-NCEP overestimates the tropospheric ozone at mid-high latitudes during winter and spring seasons. The over predicted ozone is likely the consequence of the STE that is too strong in the NCEP1 meteorological winds. At ~450hPa, a time lag of a few months between the model and observation is observed, further verifying that the STE across the tropopause is too strong. MLS data is used to validate the models in the stratosphere. The upper boundary of models is set at ~ 1hPa. The agreement between models and data is good. Figure 1 Figure 2 Figure 3 Figure 4 Seasonal Cycle Influence of Stratosphere-Troposphere Exchange Summary x 100% O3 ppbv Middle and upper tropospheric ozone is affected by the downwelling transport of air from the stratosphere, where most of ozone is produced. We use the data obtained by Earth Observing System (EOS) Tropospheric Emission Spectrometer (TES) and Microwave Limb Sounder (MLS) to study the ozone distribution from the middle troposphere to the lower stratosphere. Comparisons with model results are made. An off-line chemical transport model (MOZART-2) driven by the NCEP1 and MACCM3 circulations and the on-line model CAM-CHEM, a newly developed model at NCAR, are used to simulate the distribution of ozone from the surface to ~5 mbar. We find that the phase of the seasonal cycle of the modeled O 3 in the mid-troposphere is off by ~1-2 months compared with that of the observed O 3, while the phase between models and observations is good in the lower stratosphere. This suggests a gap of our understanding of the cross tropopause transport in the current model. The TES total column ozone agrees well with the MOD (TOMS/SBUV Merged Ozone Data) to be within ~5%, but the retrieved vertical profiles of ozone can be differed by as much as 20% from ozone sondes (Worden et al., 2007). The MOZART-2 model driven by NCEP tends to overestimate the abundance of mid-tropospheric ozone at mid-high latitudes compared with TES ozone, suggesting that the STE is too strong in the NCEP. Figure 1 Figure 2 Jan.Apr. Jul.Oct. Jan.Apr. Jul.Oct. MLS @ 68 hPa MOZART-2-MACCM3 @ 66 hPa MOZART2-NCEP @ 68 hPa CAM-CHEM @ 70 hPa TES @ 450 hPa MOZART-2-MACCM3 @ 433 hPa MOZART2-NCEP @ 435 hPa CAM-CHEM @ 433 hPa