PollyNet is a network of light radars (lidar) that use laser beams to explore the atmosphere from the ground. With its measurements it contributes to the European research infrastructure ACTRIS, which investigates aerosols, clouds and trace gases. It is coordinated by the Leibniz Institute for Tropospheric Research (TROPOS) in Leipzig. PollyNet stations in Finland, Germany, Greece, Poland, Portugal and South Korea are already continuously measuring dust in the atmosphere by laser. Further stations are planned in Cyprus, Israel, and on the Cape Verde Islands.
For the technology of the stations in Tajikistan, Cyprus and on the Cape Verde Islands, the Federal Ministry of Education and Research (BMBF) has provided almost three million euros to close observation gaps and intensify successful cooperation with these countries. Thanks to technical support from Germany and on-site support from the Academy of Sciences of the Republic of Tajikistan, the test measurements carried out as part of the CADEX project (Central Asian Dust Experiment) can now be converted into operational long-term measurements that will provide important long-term data for climate and air quality in Central Asia.
The automated Ramanlidar systems of the Polly type (POrtabLe Lidar sYstem) have been developed by TROPOS for over 15 years, used worldwide and have become central instruments at various measuring stations such as Leipzig or Punta Arenas in Chile. These lidar systems measure particle properties, optical properties of thin clouds and moisture profiles. "In recent years, the polarization lidar technique has been significantly further developed and now makes it possible to measure the environmental impact of desert and soil dust (fine dust particles) and to determine the climate effect and cloud formation (coarse particles as condensation nuclei and ice nuclei) vertically resolved," explains Dr. Dietrich Althausen of TROPOS, one of the main initiators of this technique. "In addition, the polarization lidar allows vertically resolved estimates of the concentrations of condensation and ice nuclei in a wide variety of particle mixtures." The PollyNET concept is methodologically comparable with the global aerosol measuring network AERONET (AErosol RObotic NETwork), whose solar photometer is coordinated by NASA and the University of Lille.
As part of the Central Asian Dust Experiment (CADEX), lidar measurements have been carried out since 2015 to study mineral dust over Tajikistan using a smaller, portable lidar version. The CADEX project was financed by the Federal Ministry of Education and Research within the framework of "Partnerships for Sustainable Problem Solutions in Emerging and Developing Countries". Within this framework, close scientific cooperation was established between the Physical-Technical Institute of the Academy of Sciences of Tajikistan and the Leibniz Institute for Tropospheric Research. In the meantime, the project has been honoured by the BMBF as a "lighthouse project" because it produced outstanding results. However, the CADEX project was only designed to record a few sample measurements. As a consequence, a measuring container was designed and built at TROPOS in Leipzig with the support of the BMBF, which was transported to Tajikistan by land at the end of May. With the commissioning of the PollyNet station in Dushanbe, the measurements will now be transferred to long-term observations. The long-term measurements reveal trends that only become apparent over several years. The lidar measurements in Tajikistan will thus provide important data on climate change and air quality in Central Asia.
