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Centre for Atmospheric Science

CLACE-4 Project

Instruments at Jungfraujoch, Switzerland.
Instruments at Jungfraujoch, Switzerland.

Location: Jungfraujoch, Switzerland

3580 m asl; 46.55°N, 7.98°E

Measurement Period: 15 February 2005 - 15 March 2005

Participating Institutes: PSI, IFT, University of Manchester, MPI Mainz & Uni Mainz, Tech. Uni Darmstadt, University Helsinki, EMPA, UNI Bern, DLR, EMPA, ETHZ, UNI FRANKFURT

University of Manchester Equipment: Aerosol Mass Spectrometer, GRIMM Dust Monitor, 3025 Condensation Particle Counter, Airborne Droplet Analyser, Cloud Particle Imager, Forward Scattering Spectrometer Probe, Cloud Droplet Probe, 2D Grayscale Probe, Particulate Volume Monitor, Ultrasonic Anemometer, Present Weather Sensor, Rotronics T+RH, Ambient Pressure.

The CLACE 4 project (Cloud and Aerosol Characterisation Experiment in the Free Troposphere) is one of a series of projects led by the Aerosol Research group of The Paul Scherrer Institute, and is based at the Jungfraujoch High Alpine Research Station in Switzerland. The University of Manchester (formerly UMIST) has been involved in these experiments since CLACE 2 in the summer of 2002. On each occasion we have made aerosol mass spectrometer measurements of aerosol chemical composition, and made cloud microphysical measurements using a suite of instrumentation. In CLACE 3 and 4 we also collected ice crystals using the formvar replica technique for later analysis of the ice nucleus, using Environmental Scanning Electron Microsopy (ESEM). Both the CLACE 3 and 4 projects were held during the wintertime, to study the interaction of aerosol particles with ice clouds, while the CLACE 2 project was held in the summertime, to study aerosol interaction with warm clouds. CLACE 4 is an extension of CLACE 3, with an improved set of instrumentation and operating protocols based on the experience gained during the CLACE 3 project. More details about the CLACE 3 project, and links to the web pages of the other groups involved can be found here (site is in German). A summary of CLACE 3 in English can be found here.

This page is intended to provide an introduction to the CLACE 4 project, and presents some images of the project, the area in which it is located, together with some preliminary data. Eventually references to University of Manchester publications resulting from this and previous projects in the series will be given.

Instrumentation Set Up and Results

The Aerosol Mass Spectrometer in the Sphinx Lab.
The Aerosol Mass Spectrometer in the Sphinx Lab.

The Aerosol Mass Spectrometer, 3025 Condensation Particle Counter, and GRIMM dust monitor, were all located in the main 2nd floor lab in the Sphinx building at the Jungfraujoch. Sampling was via a common switching inlet, which switched on a six minute cycle between a heated total inlet, and a <2um diameter interstitial inlet. This allowed these instruments to sample alternately, all aerosol, including those which were in cloud particles, and just those which were not activated or scavenged in cloud. Of the aerosol instrumentation from other groups, some was located on the switching inlet, some on the individual inlets and some on a counterflow virtual impactor (CVI) operated by IFT, which could be configured to separate out either small ice particles or droplets depending on the cloud conditions.

The cloud microphysics instruments were all set up outside on a roof terrace of the Sphinx building, with the data systems and control in the lab. The main microphysics instruments which need to point into wind were mounted in the centre of the roof, at a height of approximately 3m above the roof, on a pan and tilt rotator. This allowed the instruments to be moved into either of the dominating wind directions, and their inlets be alligned properly with the flow. Alignment was based on the wind direction information from the ultrasonic anemometer, mounted along with the particlulate volume monitor, on a separate none rotating mast. The cloud particle imager, forward scattering spectrometer probe, and cloud droplet probe were all aspirated by use of industrial vacuum cleaners located underneath the access platform. Flow through the inlets of these instruments was continuously monitored using venturi gauges.

An example of data from the Airborne Droplet Analyser measuring cloud droplets.
An example of data from the Airborne Droplet Analyser measuring cloud droplets.

An important objective of the CLACE 4 project was to attempt to identify the effects of different aerosol types on the cloud. It was observed during CLACE 3 that the cloud properties could change very rapidly, for example it was frequently observed that the cloud would change from fully glaciated to fully supercooled on timescales of less than 1 second. For CLACE 4 all instruments were operated with as great a temporal resolution as possible, with care taken to synchronise the time between all data systems. The cloud microphysical instrumentation and sonic anemometer were operated at a data rate of at least 10Hz, while the aerosol mass spectrometer operated at a one minute time resolution, and the GRIMM dust monitor at a six second resolution. In most cases this was a significant improvement on the temporal resolution during CLACE 3. In addition to operating at a greater temporal resolution, additional instruments were deployed, such as the present weather sensor, which is able to indicate the presence of precipitation as well as cloud, and temperature and humidity measurements were made outside, and in both the total and interstitial inlets.

Project Location

A view from the Sphinx Observatory.
A view from the Sphinx Observatory

The Jungfraujoch High Alpine Research Station is located in the Swiss Alps, in the Jungfrau region, near Interlaken, close to the mountains Eiger, Monch and Jungfrau. Jungfraujoch is actually situated on the ridge between the Monch and Jungfrau, with a view to the south down the Aletschgletcher, the longest glacier in Europe, and to the north down to Kleine Scheidegg, Interlaken, and further away Bern. Access to the site is via the Jungfraubahn mountain railway.

The research station is typically in cloud for 37% of the year, and so is an excellent location for ground based cloud studies. The remote location, and high altitude, mean that the site is not generally affected by local pollution, and often is in the free troposphere, though that depends on the prevailing meteorological conditions. Thus a variety of very clean and more polluted conditions are experienced at the site. During the winter temperatures range from about -28°C to about -5°C, and in the summer from about -10°C to 2°C, thus clouds at many different temperatures, and in both ice and liquid phases are experienced.

The remote location, low temperatures, and sometimes high wind, can make the site a hostile location in which to work, especially when working outside, but at the other extreme, when the weather is good, the location is exceptionally beautiful.

Project Publications

Clace 2

Clace 3

Clace 4

Publications from more than one CLACE project