On behalf of the Institute for Meteorology and Climate Research of the Karlsruhe Institute of Technology (KIT), and in co-operation with the Verkehrsbetriebe Karlsruhe (VBK), enviscope GmbH designed and built an instrument package for atmospheric research on top of a tramway. It is the first time that in Germany the spatial variability of air quality in an highly polluted urban area (city of Karlsruhe)  and "simultaneously" in the low contaminated surrounding rural areas (northern Black Forest) is measured.

Total view of the AERO-TRAM (Schnüffelbähnle)

The automated measurement system monitors the concentrations of the trace gases O3, NO, NOx, CO, CO2, H2O(g) as well as the total particle number and the particle size distribution over a long period of time. The system is operating autonomiously, although the operator has always access to the system through either a WiFi connection (short range) or a UMTS/3G broadband connection. Physical access to the system is possible on a 4 week schedule during regular checks of the tramway.

A large number of monitoring instruments is mounted in 3 specially designed weatherproof and air-conditioned housings on top of the tramway.

Illustration of the AERO-TRAM instrument package

Most prominent part of the instrument package is the aerosol inlet, which is located in the front of the tramway. It consists of a combined shroud and shelter assembly with a sonic anemometer for measuring the u-wind component acting on the aerosol inlet.

Illustration of the aerosol module in the front

The inlet system itself consists of an adjustable diffusor, providing isokinetic sampling conditions  at the single aerosol instrument inlets in the back of the inlet system. The measured wind data is used to determine the required position of the diffusor. Additionally it is used for adjusting the flow rate of a hi-vol blower to provide isokinetic sampling conditions at the sampling inlet in the front.

Photograph of aerosol module in the front

The shroud not only serves as a tool to parallelize the air-flow around the inlet. Additionally it is used as a shelter for the sonic anemometer when the tramway is cleaned in the washing plant. In this case also the sledge hosting the shroud assembly is retracted behind the front edge of the tramway so that the inlet system doesn't interfere with the brushes rotating in the washing plant. Please check the following short animation illustrating the functionality of the inlet system.

Animation of Inlet System functionality
(avi-clip opens in external viewer)

The AERO-TRAM is operational for 2 years starting in September 2009. It has been presented at the European Aerosol Conference (EAC) 2009 in Karlsruhe.

For more details on the scientific background please refer to the AERO-TRAM website at KIT.