The Schmücke Cloud Observatory

TROPOS is currently setting up the Schmücke Cloud Observatory (SCO) in the Thuringian Forest. Together with the Schmücke station of the Umweltbundesamt (UBA), the SCO will serve as a national facility (NF) within the European research infrastructure ACTRIS to facilitate long-term and continuous research on physical and chemical aerosol-cloud interactions. 

The observatory will consist of three stations: a central cloud station with a measurement tower at the Schmücke summit and two satellite stations in the valleys upwind and downwind of the Schmücke, near the villages of Goldlauter and Gehlberg (c.f. Figure 1). 

These stations will be equipped with state-of-the-art instruments for gas, particle, and cloud analysis, enabling comprehensive characterization of air masses before, during, and after cloud passage. With conceptual and preparatory work almost complete, construction works and implementation of measurement equipment is anticipated to be finished in 2026. 

Figure 1: Schematic representation of the concept and setup of the Schmücke Cloud Observatory (SCO) with its three measurement sites.

Scientific Scope

Aerosol particles and gases interact with clouds in many different ways. These interactions are of great importance in atmospheric chemistry and microphysics, but are not yet fully characterized and understood. 

Previous ground-based, Lagrangian-type cloud experiments at the Schmücke [Herrmann et al., 2005; Tilgner et al., 2014] provided insightful data on aqueous-phase processing, alteration of CCN activity, and modification of particle size distribution and thereby demonstrated the great potential of the sites for detailed cloud processing studies. 

Therefore, the permanent SCO was proposed and is now being established within the European research infrastructure ACTRIS, to allow for for long-term, continuous, and year-round investigation of aerosol-cloud interactions.

Setup of the SCO

The unique setup of the SCO is based on many years of experience and developments at TROPOS ACD, including the combined field measurement and modeling studies FEBUKO (2001/2002) and HCCT-2010 (2010). 

It comprises three measurement sites frequently experiencing connected airflow conditions, distributed orthogonally to the Rennsteig mountain ridge in the Thuringian Forest, along the main wind direction (cf. Figure 1).

The main site is located at the summit of Mt. Schmücke (937 m asl), where ground-based clouds form frequently (about 200 days per year), providing ideal conditions for stationary in-cloud measurements. 

The site will feature a 20-meter-tall measurement tower with an open roof-top platform and air-conditioned laboratory boxes (Figure 2a), housing state-of-the-art analytical instruments: high resolution aerosol chemical speciation monitors (ACSMs), a proton-transfer-reaction mass spectrometer (PTR-MS), mobility particle size spectrometers (MPSSs), aethalometers, trace gas monitors for CO, O3, SO2 and NOx, filter samplers for offline analysis of particle chemical composition, cloud condensation nuclei counters, a Droplet spectrometer, a particle volume monitor for the determination of the liquid water content, cloud water collectors for offline analysis of solutes, and more. 

These instruments will be installed at gas-, interstitial-, and whole-air inlets, while cloud water collectors will be mounted on the accessible rooftop for comprehensive characterization of gas, particle, and cloud phases.

Figure 2: 3D-vizualization of the measurement tower on the summit site (a). Container-based valley station at the downwind measurement site in Gehlberg (b)

Supplementing the mountain site, two container-based valley stations (Figure 2b) with similar instrumentation will be located in Goldlauter (upwind site) and Gehlberg (downwind site). 

This arrangement allows for the characterization of air masses before, during, and after cloud passage, studying chemical and physical differences influenced by aerosol-cloud interactions. 

Besides their role as permanent monitoring stations, all SCO sites are designed to host additional equipment and provide access for guest researchers, e.g. through trans-national access (TNA) and for intensive measurement campaigns. 

Implementation Status

The infrastructure for the SCO field sites is currently being set up. Most analytical instruments have been acquired, prepared, and are ready for installation at their respective field sites. 

The SCO is expected to be fully operational by early 2026, with labeling planned for Cloud in-situ and Aerosol in-situ ACTRIS components. Together with the Trace gas in-situ label of the UBA station, the Schmücke NF will cover all three ACTRIS in-situ components. 

Serving as an in-cloud observatory, the SCO mountain station's measurement tower will also be an essential field site for the Center for Cloud Water Chemistry (CCWaC), a unit of the Cloud in-situ Topical Centre (TC CIS) in ACTRIS.