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  Main research projects
 
My research is focused on improving our understanding and quantification of trace gas emissions and transport in the troposphere. For this purpose, I am using an approach integrating available observations - both in situ and satellite data - with chemistry and transport models.
I am currently involved in three main projects: 
 Analysis of the long range transport of pollution in the Northern Hemisphere
Air quality is not only a local problem. Trace gases and aerosols emitted in a specific region may be transported on long distances depending on their lifetimes, and affect air quality in a neighbouring region. This transport of pollution may have several impacts: an increase of pollution backgroung levels at the surface; an import of pollution plumes to the boundary layer, directly altering air quality; a modification of the background levels in the free troposphere, with implications for the radiative budgets.
Global, continuous observations from satellite-borne instruments are particularly well suited for the analysis of the transport pathways. The controling mechanisms and the related impacts are analysed using chemistry-transport model simulations. Howere, they are currently unable to accurately represent these impacts due to uncertainties at different levels (emissions, transport mechanisms, chemical evolution).

Specific objectives: analyse the current biases in the simulation of several trace gases (CO for example) compared to the available in situ and satellite observations (IASI in particular). One of the main aspects is the simulation of the influence of wildfires.   

Approach: I am using the LMDz-INCA global model and comparisons to the campaign in situ observations (POLARCAT in 2008, ICARTT in 2004) but also to the available satellite observations (IASI/METOP in particular since 2006). 

 LRT_Asia
LRT from Asia as viewed from satellite (top) and as
simulated by the LMDz-INCA global model (bottom).
(Turquety et al., ACP, 2008)

Related projects: I am currently involved in the POLARCAT and follow-on CLIMSLIP project (Climate impacts of short-lived pollutants in the polar regions), which aim at better understanding the transport of pollution towards the Arctic, one of the regions most sensitive to climate change. This region undergoes the influence from the large industrialized regions of the Northern Hemisphere (North America, Europe, Asia), regularly resulting in the so-called "Arctic Haze", but also of the large fires burning in the boreal forests during summer. This work follows previous analyses done in the framework of the ICARTT international campaign (2004) during my post-doc at Harvard University.

(Main collaborations: LSCE, LATMOS)
 
 Fire emissions and transport

Wildfires are one of the main sources of trace gases and aerosols. However, their impact remains poorly quantified due to uncertainties on their emissions, but also on their transport - and in particular on possible importance of pyro-convective events - and on the chemical evolution during the long range transport (ozone production, interactions between ozone and aerosols). 

schema_fireimpacts

Specific objectives: 

  • evaluate the current inventories of fire emissions and develop a method for an accurate evaluation in near-real time to support air quality forecasts; 
  • analyse the possible importance of pyro-convection;
  • study the evolution of the characteristics of fire plumes during the transport. 
Sudies at global scale for the impact of boreal fires; at regional scales in the Euro-Mediterranean region (APIFLAME project) and Mexico (Thesis S. Stromatas).

Approach: Global modeling using the LMDz-INCA global model and regional modeling using the CHIMERE model; with here again comparisons to the campaign in situ observations but also to the available satellite observations (IASI/METOP, A-Train). 

 Analysis and Prediction of the Impact of Fire pLumes on Air quality of the Mediterranean and Europe (APIFLAME) 

Forest fires are regularly burning thousands of hectares of vegetation in Europe (mainly Southern Europe, Portugal, Spain, Greece, etc.), strongly affecting local ecosystems and economies, but also air quality since vegetation burning is a major source of trace gases and aerosols.  As a lot of the species emitted have a long enough lifetime to allow long range transport, emissions may have significant regional impact on atmospheric composition. However, this impact remains poorly quantified due to large uncertainties on the emissions (extent of the areas burnt, type of vegetation burned and efficiency of the burning, emission factors for the chemical species, etc.), but also on the export processes and chemical evolution of the pollution plumes. 

APIFLAME aims at evaluating and improving simulations -- and thereby quantification -- of the impact of fires on air quality, using the CHIMERE regional pollution model and available observations. A particular attention will be given to the analysis of the trace gas and aerosol observations from satellite remote sensors (IASI/METOP and A-Train instruments CALIOP/CALIPSO and POLDER/PARASOL) which provide good horizontal and temporal coverage. Results from this project will allow the integration of this potentially extremely high pertubation in air quality forecasting systems (e.g. Prev'Air plateform at INERIS). 
IASI monitoring of CO in the pollution plume emitted by the record-breaking fires in Greece in August 2007:
IASI_CO-GreekFires2007
 (Turquety et al., Atmosph. Chem. Phys., 2009)

APIFLAME is funded by the French program PRIMEQUAL and coordinated by S. Turquety, LMD/IPSL. Partners: CEREA, INERIS, LA, LATMOS/IPSL, LOA, LSCE/IPSL.

For more info, please visit the project web page .

    Trace gas retrieval from the high resolution infrared sounders IASI

In the recent years, several satellite missions measuring the thermal infrared radiation emitted by the Earth-atmosphere system in a nadir viewing geometry have demonstrated the capabilities of such measurement technique for global monitoring of atmospheric composition (MOPITT, AIRS, TES, IASI). Combining high spectral resolution with improved spatial and temporal coverage for more accurate view of regional and local pollution will be the major objective of future missions.

I am more particularly involved in the analysis of observations by the Infrared Atmospheric Sounding Interferometer (IASI), a CNES/EUMETSAT instrument. It is a nadir viewing FTS recording high resolution IR spectra with a daily global coverage and a 25 km horizontal sampling, mounted on the European Polar System METOP satellites. The first of three successive platforms was launched in October 2006. The two following will be launched sequentially over a period of 14 years, allowing the monitoring of the evolution of the composition of the atmosphere. 

I have contributed to the development of several software for the retrieval of trace gases from IASI spectra: 

  • A near-real time retrieval algorithm based on neural networks (Turquety et al., JGR, 2004) (ozone retrieval module developed during my PhD at Service d'Aéronomie, now LATMOS);

  • Research algorithm based on the optimal estimation method, the Atmosphit software developed at ULB, used for the retrieval of any IR absorbing species (Coheur et al., JGR, 2005; Barret et al., ACP, 2005); 
  • Fast version based on OEM: the FORLI softwares developed at ULB.  I particularly contributed to the development of the FORLI-CO algorithm, for the retrieval of carbon monoxyde (Turquety et al., ACP, 2009). 
 
Specific objectives : 
I now use these retrievals in collaboration with LATMOS and ULB for scientific studies of the LRT of pollution. I also contribute to the analysis of information content for pollution studies.
Research projects :
This work is undertaken as part of the CNES-TOSCA project "Use of IASI observations for atmospheric chemistry" led by C. Clerbaux (LATMOS).

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