In the remote and pristine southernmost region of New Zealand, an extraordinary atmospheric research initiative is underway — one that promises to reshape our understanding of clouds, aerosols, and their intricate interplay with climate systems. The “goSouth-2” campaign, a collaboration between international partners including the Leibniz Institute for Tropospheric Research (TROPOS) and the University of Leipzig, embarks on an ambitious project to study the unique atmospheric dynamics over this relatively unpolluted but accessible area for a sustained period of eighteen months. This expedition aims to unravel the mysteries surrounding cloud formation in some of Earth’s cleanest air masses, shedding light on critical gaps in climate forecasting models.
The geographic uniqueness of the southern tip of New Zealand’s South Island offers an unparalleled natural laboratory. This area experiences dominant air masses originating from the Antarctic and the Southern Ocean, bringing largely uncontaminated, aerosol-poor air. Aerosols — tiny particles suspended in the atmosphere — act as nuclei for cloud droplet and ice crystal formation, but their scarcity here presents a challenge for existing weather and climate models. Unlike other regions burdened with mineral dust, industrial pollutants, and biomass smoke, this environment provides scientists an opportunity to study cloud physics in an extreme clean-air setting seldom replicated on the planet.
Challenges in accurately forecasting weather patterns over the southern hemisphere, particularly relating to cloud development and their radiative impact, have persisted for years. Climate models are often calibrated with data drawn from the northern hemisphere, where aerosol sources are far more abundant and pollution profiles markedly different. This mismatch leads to systemic errors in simulations of cloud microphysics and precipitation in the south. Professor Adrian McDonald from the University of Canterbury elaborates that these inaccuracies directly affect hydrological predictions and modulate the energy exchanges between the atmosphere and ocean, highlighting the urgent need for region-specific data.
The “goSouth-2” campaign is not an isolated endeavor. Rather, it is part of a broader, integrated effort including airborne missions and marine expeditions that together piece together the complex atmospheric puzzle. The German research aircraft HALO will execute a major flight campaign named “HALO-South” in late 2025, surveying cloud-aerosol interactions over the Southern Ocean with unprecedented detail. Complementing airborne data, research vessels Sonne and Polarstern are planned to conduct expeditions in 2027 and 2028 to further investigate the region’s atmospheric composition and dynamics, establishing a holistic picture of the Southern Ocean atmosphere.
Essential to these efforts is the deployment of an arsenal of cutting-edge remote sensing instruments. Three containers of specialized measurement equipment were transported from Leipzig to Invercargill in April, including the mobile Leipzig Aerosol and Cloud Remote Observations System (LACROS) and cloud radar systems from the University of Leipzig. LACROS integrates multiple radar and lidar technologies, allowing the team to scan the vertical distribution and temporal evolution of aerosols and clouds with remarkable spatial accuracy and temporal frequency. These synchronous measurements are vital to differentiate between ice crystals, liquid droplets, and various aerosol types — from natural sea salt particles to anthropogenic pollutants.
One of the most innovative tools employed in this campaign is the PollyXT fluorescence lidar, unique in the southern hemisphere. This instrument can detect and classify bioaerosols such as pollen and smoke from forest fires by exploiting their intrinsic fluorescence properties, distinguishing them from industrial or volcanic aerosols. This capability provides novel insights into the sources and transformations of aerosols, enhancing the ability to track episodic pollution events originating from distant continents like Africa, South America, and Australia, which intermittently influence New Zealand’s air quality at high altitudes.
The co-location of the campaign instruments at the Invercargill Observatory — situated adjacent to the local airport — is strategic. The observatory, operated by New Zealand’s MetService, offers long-term meteorological data and routine radiosonde launches, thereby enriching the remote sensing dataset with in-situ meteorological observations. This synergy between ground-based instruments and local weather monitoring infrastructure ensures high-quality, continuous atmospheric profiling crucial for model evaluation. The collaboration with MetService exemplifies the seamless integration of international scientific expertise and indigenous infrastructure for sophisticated atmospheric research.
Another distinct aspect of goSouth-2 is its focus on capturing the contrasts in aerosol loading between pristine Antarctic air and aerosol-enriched air masses originating from Australia. Such variations, expected roughly a quarter of the time, provide a natural experiment to disentangle the mechanisms by which aerosols influence cloud microphysics, radiative properties, and precipitation processes. By meticulously comparing cloud characteristics under clean versus polluted conditions, scientists hope to refine parameterizations in climate models that currently struggle with accurately simulating these subtle but critical effects.
The ACADIA project, embedded within goSouth-2 and funded by the German Research Foundation, specifically targets the atmospheric influence of minor air quality variations on cloud formation. Enabled by support for doctoral researchers, this initiative is pioneering the use of machine learning techniques to simulate cloud thermodynamics and solar radiation interactions over the Southern Ocean. Such computational advances promise breakthroughs in representing cloud-climate feedbacks in regional and global models, with direct implications for improving climate resilience policies in New Zealand and beyond.
Supporting the aerial campaigns, complementary ground-based measurements are conducted at the Tāwhaki National Aerospace Centre near Christchurch. Here, advanced Doppler lidar, ceilometer, micro-rain radar, and cloud radar instruments enhance observational coverage. These facilities augment the vertical profiling capabilities and capture dynamic atmospheric processes across multiple spatial scales. Regular radiosonde launches synchronized with HALO flights enable the collection of thermodynamic profiles critical for validating remote sensing data and fine-tuning model inputs.
The coordinated measurements from the goSouth-2 campaign dovetail into additional international efforts, including the European Union’s CleanCloud project and the Leibniz Science Campus “Smoke and Bioaerosols in Climate Change.” These collaborations address the broader context of aerosol-cloud interactions under evolving climate conditions, particularly emphasizing sources such as forest fires that are increasing in intensity globally. Integration with data from the ESA’s EarthCARE satellite mission, launched in 2024, enables cross-validation of ground and airborne observations with global spaceborne lidar and radar datasets, fostering a comprehensive understanding of cloud-aerosol processes on a planetary scale.
Looking ahead, the launch of goSouth-2 marks the beginning of a renewed era of intensive cooperation between Germany and New Zealand in atmospheric sciences. The subsequent HALO-South flights, combined with ground-based and shipborne expeditions, comprise one of the most extensive coordinated research efforts focusing on Southern Hemisphere clouds and aerosols. Beyond scientific insights, the campaign promises strong community engagement, with public events planned in Invercargill and Christchurch to share findings and inspire future generations of scientists.
This collaborative enterprise showcases the power of multinational research initiatives tackling global climate challenges through regional atmospheric studies. By unlocking the secrets of clouds in one of Earth’s cleanest atmospheric environments, goSouth-2 and its partner projects seek to calibrate climate models more accurately, ultimately enhancing predictive capabilities crucial for societies worldwide grappling with climate change.
Subject of Research: Not applicable
Image Credits: Ronny Engelmann, TROPOS
