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EarthCARE Satellite’s Atmospheric Lidar Enhances Climate Research

The successful activation of the atmospheric lidar ATLID marks a significant milestone for the EarthCARE satellite, which was launched in May. This instrument, developed through a collaborative effort between the European Space Agency (ESA) and the Japanese Space Agency (JAXA), is designed to provide unprecedented precision in measuring clouds, aerosols, and radiation.

Contributions from the Leibniz Institute for Tropospheric Research (TROPOS) are critical to the mission, particularly through the development of algorithms that interpret measurements from the lidar. The large-scale measurement campaign, involving approximately 50 ground stations across Europe and beyond, is essential for enhancing the accuracy of the satellite’s data, facilitating detailed analysis of aerosol particles and clouds using advanced remote sensing technologies such as lidar and radar.

For further details on this research, readers can refer to a recent publication in the Bulletin of the American Meteorological Society.

Key Features of EarthCARE

EarthCARE is outfitted with four cutting-edge instruments: a cloud profiling radar, atmospheric lidar, broadband radiometer, and multispectral imager. These tools work in concert to gather diverse measurements that elucidate the interactions of clouds and aerosols with solar energy and thermal radiation. Understanding these dynamics is pivotal for assessing climate change’s impact on Earth’s energy balance and predicting future climatic behavior.

Since its launch into orbit on May 29, 2024, EarthCARE has been actively delivering data. Within a month, the satellite produced its first cloud profiling radar images, followed shortly by outputs from its broadband radiometer, multispectral imager, and finally the atmospheric lidar in August. This lidar captures comprehensive vertical profiles of atmospheric aerosols and clouds, contributing vital information about their characteristics across various global regions.

Aerosols, consisting of minute particles from both natural and anthropogenic sources, play a fundamental role in the atmosphere’s composition. The lidar utilizes short bursts of ultraviolet light that are scattered by these particles, allowing scientists to determine their distance, concentration, and type through careful analysis of the light’s return signal. This capability is instrumental for cataloging aerosol and cloud distributions, enhancing our understanding of their properties such as height, thickness, and optical characteristics.

The integration of data from the lidar with that from the other EarthCARE instruments is crucial for obtaining a holistic view of how aerosols and clouds influence Earth’s energy equilibrium. A new model, termed the “Hybrid End-to-End Aerosol Classification” (HETEAC), has been specifically crafted to facilitate seamless aerosol classification across the suite of instruments, ensuring that multi-faceted data analysis is coherent and meaningful. Notably, the ATLID lidar will play a key role in advancing air quality forecasting methodologies.

Ulla Wandinger, a key figure in ATLID’s development, expressed her excitement over the initial measurements, stating that the “wealth of data and detailed insight into atmospheric structures are absolutely impressive.” EarthCARE holds the promise of significantly advancing scientific understanding of aerosol-cloud interactions and broader climate research initiatives.

The initial images obtained in August illustrate the variety of aerosol and cloud structures in the atmosphere, capturing phenomena such as Polar Stratospheric Clouds (PSC) over Antarctica and the impacts of Tropical Storm Debby in the Gulf of Mexico, as well as smoke plumes from Canadian wildfires.

Simonetta Cheli, ESA’s Director of Earth Observation Programmes, noted the significance of the atmospheric lidar’s contributions, emphasizing that its data will enable deeper insights into the vertical distribution of atmospheric components, thereby enhancing scientific knowledge regarding Earth’s climatic dynamics.

Collaborative Measurement Campaigns Across Atlantic and Europe

To enhance the interpretation and application of data generated by the new instruments, extensive ground-based and airborne validation efforts are underway. These international measurement campaigns are vital for ensuring that satellite data is robust and accurate across varying conditions.

Throughout November, the German research aircraft HALO is set to conduct multiple flights operating in tandem with the EarthCARE satellite, originating from locations such as Cabo Verde, Barbados, and Oberpfaffenhofen, Germany. This validation mission, known as HALO-PERCUSION, is a joint endeavor led by the German Aerospace Center (DLR) in collaboration with the Max Planck Institute for Meteorology (MPI-M) and several prominent research institutions, including the University of Leipzig.

Complementing this initiative is the CLARINET (CLoud and Aerosol Remote sensing for EarThcare) project, where TROPOS scientists employ the newly established ACTRIS remote sensing station at Cabo Verde’s Atmospheric Observatory to validate EarthCARE’s findings in the tropical Atlantic, contrasting them with historic data sets.

The ACTRIS network’s ground stations have been strategically expanded and updated in recent years to optimize the calibration of data from EarthCARE, facilitating sophisticated analyses of aerosols and clouds through lidar and radar technologies. This expansive network of around 50 stations ensures that EarthCARE frequently passes directly over at least one station, providing continuous and relevant data interaction due to its low-Earth orbital pattern, which revisits the same geographic locations every 25 days.

Dr. Holger Baars of TROPOS, coordinating the campaign from Leipzig, recounted the two-month preparatory phase of simulated overflight measurements that was crucial for implementing this intricate campaign. He highlighted the varied backgrounds of the ACTRIS stations in terms of data validation, expressing eagerness for the forthcoming comparisons between ground-based observations and EarthCARE’s satellite data.

Stations contributing to this initiative include those operated by the German Weather Service (DWD), the University of Cologne, and various other esteemed institutions providing critical observations from diverse geographical locales, including the Arctic and several sites within the Earth’s dust belt.

More information: Paolo Laj et al., Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS): The European Research Infrastructure Supporting Atmospheric Science, Bulletin of the American Meteorological Society (2024). DOI: 10.1175/BAMS-D-23-0064.1

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