Inn Valley Target Area

Seven eddy-covariance stations, each instrumented with a 3D sonic anemometer and infrared gas analyzer at least at one height, are operated by the University of Innsbruck about 20 km east of Innsbruck (i-Box). The locations cover different topographic (valley floor, mountain top, north- and south-facing sidewalls, steep and moderate slopes) and different land-use (grassland, agricultural, dwarf pine) characteristics. Six of the stations are full surface-energy balance stations with four-component radiation and ground heat flux measurements.

Weather stations in the IVTA are operated by the Austrian national weather service (GeoSphere Austria), the German national weather service (Deutscher Wetterdienst, DWD) in the valley exit region, the avalanche warning service (Lawinenwarndienst Tirol) and the hydrological service of the state of Tyrol (Hydrographischer Dienst Tirol), with more than 150 stations in total.

Austro Control operates a dual-polarisation Doppler C-band radar at Patscherkofel.

The surface-based remote sensing and radiosonde launch sites of the TOC Backbone in the IVTA are shown in Figure 1. As the planning for the TOC progresses, site locations may change slightly and additional sites may be added. The goal is to monitor the vertical structure of the valley atmosphere at different locations along the valley. To this end, Doppler wind lidars will be operated at Kufstein near the valley exit by GeoSphere Austria, at Radfeld by Meteo Swiss, at Kolsass by the University of Innsbruck, and at Innsbruck by KIT/IMK-IFU. At Innsbruck, radiosoundings are launched operationally at the airport once per day by Austro Control. During the summer EOP, an additional Doppler wind lidar will be operated at Brannenburg downstream of the valley exit by DWD and two lidars towards the end of the Weer Valley, a small tributary valley of the Inn Valley, by DLR. Vertical temperature and humidity profiles will be measured using a Raman Lidar and a microwave profiler at Innsbruck and Kolsass, respectively. Figure 1: Surface-based remote sensing and radiosonde launch sites of the TOC Backbone in the IVTA. Pink markers indicate locations that are considered important, but for which instrumentation has not been secured yet.

The University of Grenoble and the University of Innsbruck will be deploying multiple instruments on a steep north-facing slope to study katabatic flows, turbulence in katabatic flows, advection, and local flow heterogeneity. The slope is characterized by a relatively homogeneous and approximately 400-m long stretch of Alpine meadow, with a line of trees to either side of the slope at a distance of about 70 m and a forest starting about 250 m up the slope. One of the i-Box stations has been operational since 2013 at the site. Instrumentation will be expanded with up to 10 automatic weather stations, multiple surface-energy balance stations including up to 9 sonic anemometers and a Pitot tube, and a distributed temperature sensing system.
Contacts: Christophe Brun (Université Grenoble Alpes) and Manuela Lehner (University of Innsbruck).

DLR and the University of Innsbruck will be deploying two Doppler wind lidars, a surface-energy balance station, 10 automatic weather stations, and several temperature sensors in the upper part of the Weer Valley (Nafingalm), a small tributary valley of the Inn Valley. Additional measurements will be conducted with a swarm of UAVs to study slope and valley winds in this small valley, their interactions, and the impact of larger-scale circulations.
Contacts: Norman Wildmann (DLR) and Alexander Gohm (University of Innsbruck).

It took place in summer 2022, with measurement sites at Kolsass and surroundings, in the Weer Valley (Nafingalm), in Innsbruck, and the exit of the Inn Valley near Kufstein and Brannenburg. PC22 included contributions from KIT/IMK-TRO, DLR, DWD, GeoSphere Austria, and the University of Innsbruck. The goals were mainly to test (new) instruments and measurement sites for the TOC. Activities included lidar observations of the vertical wind structure at four different locations along the valley; scanning lidar observations of the nocturnal outflow from the Weer Valley into the Inn Valley; a lidar intercomparison study, distributed temperature sensing measurements; observations of the valley atmosphere in a small tributary valley using UAS, AWS, and temperature/humidity sensors; testing of a new Raman lidar and deployment of a co-located Doppler lidar; and detailed observations of the valley exit jet using multiple surface stations, a wind lidar, and radiosoundings. An overview of the measurement campaign and first results can be found in Pfister et al. (2023).
Contacts: Lena Pfister and Alexander Gohm, University of Innsbruck.

The University of Grenoble and the University of Innsbruck will conduct a test campaign at the beginning of 2024 to test the measurement setup on the steep north-facing slope for the TOC winter EOP.
Contacts: Ivana Stiperski and Manuela Lehner, University of Innsbruck

A subgroup of the MoBL WG is performing an intercomparison of mesoscale models for a case study of thermally driven flows in the Inn Valley selected from the CROSSINN field campaign to evaluate the model skill in different phases of the diurnal evolution of the convective mountain boundary layer (MoBL). The participating models include ICON, AROME, WRF, and GRAMM-SCI.
Contact: Lorenzo Giovannini, University of Trento.

Several case studies at kilometer and hectometer resolution are performed within Master’s theses at the University of Innsbruck to study the impact of model resolution, boundary layer parameterization, land cover, and tributary valleys on the representation of MoBL processes.
Contact: Alexander Gohm and Manuela Lehner, University of Innsbruck.

As part of the ASTER project (University of Innsbruck, University of Trento, University of Bolzano) WRF simulations with a grid spacing of 1 km are performed for the Inn Valley to evaluate the impact of the land-use data set, boundary-layer parameterizations, initial soil fields, and the model evaluation strategy on the model’s representation of the surface-energy balance and the valley atmosphere.
Contact: Manuela Lehner, University of Innsbruck.

Investigating the surface energy balance over mountain areas is a collaborative project between the University of Innsbruck, University of Trento and EURAC with the objective to investigate the surface energy balance (non-)closure in highly complex terrain and the role of advection. The UIBK contribution focuses on i-Box sites and generalization for different site characteristics.
Funding: EGTC European Region Tyrol-South Tyrol-Trentino, Austrian Science Fund FWF - IPN 187-N.
PIs: Lorenzo Giovannini (University of Trento), Mathias Rotach (University of Innsbruck), Stefano Tondini (EURAC).

The objective of Near-surface turbulent exchange in the stable mountain boundary layer is to analyze the relative contributions of mountain-specific processes to turbulence production and damping in the stable boundary layer of the Inn Valley, analyzing i-Box data. Turbulent exchange is typically weak and intermittent under stable conditions, but wind shear associated with slope and valley winds can contribute to turbulence production even under otherwise undisturbed conditions.
Funding: Austrian Science Fund (FWF): V 791-N.
PI: M. Lehner, University of Innsbruck.

The objective of this project is a detailed process-based understanding of the uptake of carbonyl sulfide (COS) by a Scots Pine forest in order to narrow down the uncertainties that still surround the application of COS as a proxy for gross primary productivity. To this end eddy covariance COS and CO2 flux measurements are combined with chamber measurements on soils, branches, stems and needles and a process-based multi-layer canopy model. Field activities take place at the FAIR site.
PI: Georg Wohlfahrt, University of Innsbruck.

In the The future of mountain forests response to a drier climate project two PhD theses will investigate the forest-atmosphere exchange of biogenic volatile organic compounds and use a multiple constraints approach to gross primary productivity. Field activities take place at the FAIR site.
PIs: Stefan Mayr, Thomas Karl, and Georg Wohlfahrt (University of Innsbruck).