Objectives and Project Description:

Isolated convective clouds, mesoscale convection in the vicinity of cold fronts, and uplifting of air masses by the large-scale circulation are effective in rapidly transporting trace gases emitted or generated in the boundary layer (BL) into the upper troposphere (UT). Once in the UT, the trace gases have substantially longer lifetimes and can be transported over long distances. Oxidation products, in particular ozone (exported from the BL or formed in the UT), can therefore influence the oxidizing capacity and the radiative balance of the UT at super-regional scales. However, the overall impact of these processes on the distribution and budget of trace gases in the UT over Europe is presently only poorly known.

Therefore, the main objectives of the proposed project are:

to investigate the relative importance of convective clouds, frontal systems and long-range advection in transporting nitrogen oxides (NO_X=NO+NO₂), HO_X precursors, and other chemical species into the UT over Europe including variation with season;
to carry out the first UT peroxy radical measurements over Europe using a novel experimental method;
to quantify the total convective transport of NO_X and other ozone precursors over Europe;
to compare the contribution from convection to the trace gas budget of the UT with the contributions by aircraft emissions and lightning;
to analyse perturbations of the UT by aged pollution layers formed by convection or frontal uplift upwind of Europe;
to investigate the impact of convectively uplifted trace chemicals on the photochemical balance of the UT.

The proposed project includes a combination of aircraft observations with a comprehensive suite of chemical and meteorological in situ measurements, analysis of satellite data, and chemical and transport modeling. This requires a collaboration of groups from different institutions (DLR, TUM, IFU, and MPI-K), focusing their expertise in different research fields on one common goal.

Two major field experiments for summer and winter conditions (in November 2001 and summer 2002) with the DLR research aircraft Falcon are foreseen. The flight planning will be supported by the use of trajectory calculations and satellite images. To be able to investigate convection over different surface source regions, it is planned to make flights over strongly polluted areas (western Germany, northern Italy, Paris and London) and less polluted areas (western France and Iberian Peninsula) during unstable weather situations with focus on the UT (7-12 km). The flight pattern will be designed according to the specific meteorological conditions including traverses of thundercloud anvils, cold fronts and individual cumulus clouds. The DLR Falcon has a ceiling altitude of 13 km allowing sampling in the outflow of deep convection in the UT.

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