Work package no 7: Gas exchange (CO₂, H₂O, and related trace gases) between the experimental sites and the adjacent atmosphere

Over each of the three composite experimental sites along the transect across the Eastern Alps a box volume will be defined which covers the ecosystem complexes of the catchment. The upper boundary is given by the flight height of the aircraft, which is chosen approximately at the constant flux layer top. The horizontal fluxes from and to the box will be determined by means of a combination of scintillation anemometry and open path absorption spectroscopy. A setup of four to five optical beams are planned to surround the box. The vertical fluxes will be measured by means of the eddy correlation method, xylem sap flux measurements for the determination of water flux from single trees to the atmosphere, continuous bulk sampling for the measurement of deposition fluxes and the aircraft measurements flying on a constant height. The long-term spatial and temporal carbon water relation of the vegetation under consideration will be characterized by means of the ¹³C isotope ratio (see work package no6). The following equipments will be used to determine the various fluxes between the landscape and the atmosphere:

• The direct measurement of fluxes through the valley will be based on two parallel light beams, one for a DOAS system (differential optical absorption spectroscopy) and one for a scintillation anemometer system (SCIDAR, scintillation detection and ranging).
• An instrumented motorglider will be equipped with instruments for measuring NO₂, O₃, temperature, humidity and pressure, wind speed and direction and up to 20 VOC species with an on-board GC. In addition, electropolished steel-bottles can be filled and analysed after the flight.
• Bulk samplers for the determination of the deposition of nitrogen compounds and ground stations for continuous measurements of water and NO₂ will be used to specify the atmospheric environment of the sites.

Back