ATMOCHEM - POllution: MODeling and ObseRvatiOns (POMODORO)
Zusammenfassung der Projektergebnisse
In the frame of the POMODORO project (Pollution Modelling and Observations) in-situ and satellite observations as well as model simulations investigated transport and the chemical effect of pollution in the upper troposphere. The following questions were adressed: What is the effect of biomass burning on the chemical composition of the global atmosphere? What is the temporal and spatial extent of tropospheric influence in the stratosphere? Which pollution sources affcet the ozone budget of the tropopause region ? To address these questions simulations with the global atmospheric chemistry general circulation model EMAC (ECHAM5/MESSy atmospheric chemistry version) were performed. For the GCM a CTM mode was evaluated to apply the model setup for the POMODORO project. Furthermore the perturbation method which applies small perturbations to an emission field has been compared to a tagging method. The global simuulations were evaluated with satellite observations from MOPIITT and SCIAMACHY with focus on the effect of biomass burning on tropospheric CO. In addition, in-situ NMHC data from CARIBIC were analysed to investigate pollution characteristics over Eastern Asia. Furthermore, statistical trajectory analyses were performed to investigate the depths of tropospheric influence in the extratropical lowermost stratosphere. The global model studies indicate 1) that the method of small perturbations of the emission fields is just an approximation of the full chemistry and the non-vanishing residuals are inherent of the method. A method to quantify this residual is proposed 2) that stratospheric impact of biomass burning in the extratropics does mainly affect the extratropical tropopause region and does not penetrate deep into the stratosphere 3) that biomass burning in the tropics mainly affects the lowest tropical stratosphere with a relatively small effect on ozone. The comparison with satellite data shows 4) that CO-emissions over east Asia are strongly underestimated 5) that different models using the same emission inventory show in general a good agreement of the CO column densitiy compared to satellite observations. However, over central Africa significant differences between some of the models and the observations appear. The reason for these deviations are under investigation and might be related to the convection scheme or the emission height of the emissions. Trajectory studies, which have been initialized to investigate the time scale and depth of troposphere to stratosphere transport in the extratropics, indicate 6) that the tropopause region (ExTL) in the extratropics is dominated by short transport time scales (< 35 days) and frequent exchange, which is in accordance with result 2) 7) that the time scales for transport in the stratosphere above the tropopause region (ExTL) show a strong seasonality. The region is dominated by air masses, which have longer transport time scales than 35 days and contains air from the TTL (tropical tropopause layer) 8) that the fraction of younger ('age' < 35 days) to older air during summer is significantly shifted towards younger air, mainly due to the seasonal cycle of stratospheric downwelling in the background stratosphere. 9) MOPITT satellite data are a valluable tool for long-term analyses of sources of CO and biomass burning, howveer, trend analyses are critical due to artificial effects from the drifting averaging kernel for some levels (version 5 data, NIR and thermal IR). 10) The comparison of simulations in a new nested model setup highlight the importance of model resolution for effects of transport and mixing within the troposphere for the understanding of dynamical effects which in turn affect chemistry. First results indicate, that typical resolutions of current global models (T106) are not sufficient to capture the dynamical processes which control surface ozone.
Projektbezogene Publikationen (Auswahl)
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On the attribution of contributions of atmospheric trace gases to emissions in atmospheric model applications, Geosci. Model Dev., 3, 487-499, 2010
Grewe, V., Tsati, E., and Hoor, P.
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Transport timescales and tracer properties in the extratropical UTLS, Atmos. Chem. Phys., 10, 7929-7944, 2010
Hoor, P., Wernli, H., Hegglin, M.I., and Bönisch, H.
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A quasi chemistrytransport model mode for EMAC, Geosci. Model Dev., 4, 195-206, 2011
Deckert, R., Jöckel, P., Grewe, V., Gottschaldt, K.-D., and Hoor, P.
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Application of SCIAMACHY and MOPITT CO total column measurements to evaluate model results over biomass burning regions and Eastern China, Atmos. Chem. Phys., 11, 6083-6114, 2011
Liu, C., Beirle, S., Butler, T., Liu, J., Hoor, P., Jöckel, P., Penning de Vries, M., Pozzer, A., Frankenberg, C., Lawrence, M. G., Lelieveld, J., Platt, U., and Wagner, T.
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Temporal change in averaging kernels as a source of uncertainty in trend estimates of carbon monoxide retrieved from MOPITT, Atmos. Chem. Phys. Discuss.,13, 20319-20340, 2013
Yoon, J., Pozzer, A., Hoor,P., Chang,D.Y., Beirle, S., Wagner, T., Schloegl, S., Lelieveld, J., and Worden, H.M.
