This green laser beam illuminates the night sky over New Zealand. The research facility is in the small town of Invercargill in the far south of New Zealand, which is one of the most untouched regions in the world. The air on the southern tip of the South Island contains almost no aerosols such as pollen, mineral dust, smoke from forest fires or particles from industry and traffic. Only occasionally the wind drives such aerosols with air masses from Australia, Africa or South America to New Zealand. The particles then act as nucleation germs on which water vapor condenses and clouds form.
Because of the constant change of very clean and dirty air, the area around Invercargill is particularly suitable for researching atmosphere and clouds. For seven years, the scientists have built up modern, ultra-precise radar and lidar measuring devices in order to collect data from aerosols, clouds and precipitation for a year and a half. The laser light of the Pollyxt Lidar system is reflected on the cloud germs, from which the position and nature of the aerosols can be calculated in the sky.
In particular, the researchers want to find out how clouds develop in clean air and how cloud formation changes when the air quality deteriorates only slightly. In addition to the remote sensing by radar and laser from the ground, research aircraft and ships are also used, which will examine the atmosphere of the southern ocean on the edge of the Antarctic in the coming years. The majority of the clean air masses that move towards New Zealand come from this uninhabited region.
In the future, the data should help improve global weather and climate models and to create more reliable forecasts for the southern hemisphere. “Because measurement data from the southern hemisphere are missing, the models used for New Zealand are often calibrated with data from other regions, especially from the northern hemisphere, which leads to errors,” explains Adrian McDonald from the University of Canterbury in Christchurch. So far, the rain and climate forecasts for New Zealand have been inaccurate.
