|EULINOX||funded by the European Community
through the Environment and Climate programme
The general objective of the project is to understand and quantify the contributions from thunderstorm lightning-induced sources of nitrogen oxides (NOx) to the composition of the atmosphere over Europe. The objective will be addressed by field experiments (including aircraft measurements) and modelling studies both, at regional scale (Southern Germany) and at the scales of Western Europe.
During the EULINOX field campaign in summer 98 standard meteorological parameters (pressure, temperature, humidity, wind), condensation nuclei, as well as the concentrations of trace gases like NOx, CO2, O3 or CO were measured on board a FALCON aircraft which was able to penetrate thunderstorm anvils. Radiation measurements were also performed by the aircraft in order to determine the NO2 photolysis rate. Lower level chemical measurements of NO, NO2, CO2 and O3 concentrations were provided by a DO-228 aircraft during the regional scale flights (pressure, temperature and humidity are also available).
The radar structure of the precipitation was measured by the polarisation diversity radar POLDIRAD of DLR and by the Doppler radar of the German Weather Service at Hohenpeißenberg (HP). The polarimetric data allow to infer the hydrometeor type. Both radar did also perform Doppler measurements in order to enable a dual-Doppler analysis of the storms three-dimensional wind field.
The three-dimensional flash structure was detected by ONERA's interferometer (ITF3D). The system measures the VHF radiation emitted from negative discharges in a lightning flash. The ITF3D consists of two independent remote stations, located at a distance of about 50 km. Data from an LPATS (Lightning Position and Tracking System) system were also available for the area of the local experiment. A network of 10 automatically recording weather stations operated by the University of Munich was installed in the special observation area (SOA) west of Munich.
Figure 1. Map of local experimental area around the radar and interferometer sites west of Munich.
The large scale NOx concentration fields were measured during cross-frontal flights towards eastern and southern Europe. European radar and lightning data were used for starting trajectory calculations by KNMI's weather forecasting model thus allowing for an optimum flight planning. Moreover, forecasts of NOx distributions over Europe were obtained from NILU's chemical transport model.
The experimental data will be evaluated by searching for parameterisations (dependencies and correlations) of the lightning activity (different phases of a flash or lightning frequency) and the associated NOx production as depending on parameters conventionally available operationally on larger scales (Cloud depth, CAPE, structures from radar and satellite data). The new experimental evidence from the EULINOX field studies will be used to compare the new formulations with existing parameterisations.
The parameterisations are then tested against the aircraft measurements using models with different scale representation. The models are subdivided into models at cloud scale and hemispheric or global scale models. The mesoscale models allow to study the dynamics and microphysics of an individual thunderstorm in such detail that the transport of LNOx (lightning produced NOx) originating from a well defined single flash can be followed. European, hemispheric and global scale models enable a comparison of the LNOx distribution according to the large scale parameterisations with the airborne measurements. Conventional parameterisations as already implemented in the models, as well as new formulations derived from the EULINOX measurements will be tested. The more detailed cloud scale results (e.g. the flash type or the height-dependence of the LNOx sources) will be checked for their ability to be extended to the larger scale.
In a final step a new inventory of European lightning NOx production and an assessment of the environmental implications will be provided. After having established an optimum LNOx parameterisation these results will be used to evaluate the data from the total experimental period with respect to the total LNOx production over Western Europe. The LNOx will be compared to NOx produced from aircraft and ground sources, the impact of the LNOx on the ozone concentration as relevant for climate assessment studies will be addressed.