Tropospheric ozone over Siberia in spring 2010: remote influences and stratospheric intrusion

International audienceWe have identified and characterised different factors influencing the tropospheric ozone over Siberia during spring 2010. This was done by analysing in-situ measurements of ozone, carbon dioxide, carbon monoxide, and methane mixing ratios measured by continuous analysers during an intensive airborne measurement campaign of the YAK-AEROSIB project, carried out between 15 and 18 April 2010. The analysis and interpretation of the observations, spanning 3000 km and stretching from 800 to 6700 m above ground level, were enhanced using the Lagrangian model FLEXPART to simulate backward air mass transport. The analysis of trace gas variability and simulated origin of air masses showed that plumes coming from east and west of the west Siberian plain and from north-eastern China related to biomass burning and anthropogenic activity had enhanced ozone mixing ratios during transport. In one case, low ozone mixing ratios were observed over a large region in the upper troposphere above 5500 m. The air mass was transported from the marine boundary layer over the Norwegian Sea where O3 background concentrations are low in the spring. The transport was coherent over thousands of kilometres, with no significant mixing with mid-upper troposphere air masses rich in O3. Finally, the stratospheric source of ozone to the troposphere was observed directly in a well-defined stratospheric intrusion. Analysis of this event suggests an input of 2.56±0.29×107 kg of ozone associated with a regional downward flux of 9.75±2.9×1010 molecules cm−2 s−1, smaller than hemispheric climatology

Assessing the near surface sensitivity of SCIAMACHY atmospheric CO2 retrieved using (FSI) WFM-DOAS

Satellite observations of atmospheric CO2 offer the potential to identify regional carbon surface sources and sinks and to investigate carbon cycle processes. The extent to which satellite measurements are useful however, depends on the near surface sensitivity of the chosen sensor. In this paper, the capability of the SCIAMACHY instrument on board ENVISAT, to observe lower tropospheric and surface CO2 variability is examined. To achieve this, atmospheric CO2 retrieved from SCIAMACHY near infrared (NIR) spectral measurements, using the Full Spectral Initiation (FSI) WFMDOAS algorithm, is compared to in-situ aircraft observations over Siberia and additionally to tower and surface CO2 data over Mongolia, Europe and North America. Preliminary validation of daily averaged SCIAMACHY/FSI CO2 against ground based Fourier Transform Spectrometer (FTS) column measurements made at Park Falls, reveal a negative bias of about −2.0% for collocated measurements within +/-1.0 of the site. However, at this spatial threshold SCIAMACHY can only capture the variability of the FTS observations at monthly timescales. To observe day to day variability of the FTS observations, the collocation limits must be increased. Furthermore, comparisons to in-situ CO2 observations demonstrate that SCIAMACHY is capable of observing a seasonal signal that is representative of lower tropospheric variability on (at least) monthly timescales. Out of seventeen time series comparisons, eleven have correlation coefficients of 0.7 or more, and have similar seasonal cycle amplitudes. Additional evidence of the near surface sensitivity of SCIAMACHY, is provided through the significant correlation of FSI derived CO2 with MODIS vegetation indices at over twenty selected locations in the United States. The SCIAMACHY/MODIS comparison reveals that at many of the sites, the amount of CO2 variability is coincident with the amount of vegetation activity. The presented analysis suggests that SCIAMACHY has the potential to detect CO2 variability within the lowermost troposphere arising from the activity of the terrestrial biosphere

A review of the remote sensing of lower tropospheric thermodynamic profiles and its indispensable role for the understanding and the simulation of water and energy cycles

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Abstracts of the 6th FECS Conference 1998 Lectures

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