Data gathered by a meteorological research aircraft have been used to verify accuracy of remote sounding instruments of weather satellites

Remote sounding improves climate change predictions

German researchers are trying to improve understanding of behaviour of water in the troposphere by combining satellite data with in-situ measurements.

During a recent data-gathering campaign in the Canary Islands, the team from the Karlsruhe Institute of Technology (KIT) has managed for the first time to verify the accuracy of data obtained by remote sounding instruments aboard satellites by comparing them with data obtained by a research aircraft flying through the atmosphere.

“Water evaporation and condensation processes as well as the strong greenhouse effect of water vapour and clouds decisively influence the energy balance of the atmosphere and the entire planet,” said Matthias Schneider from the KIT Institute of Meteorology and Climate Research (IMK). “The complex water cycle has to be known better to understand our climate and to reliably estimate its development.”

The amount of water in the troposphere, the bottom layer of the Earth’s atmosphere, plays a crucial role in determining the weather and the progress of climate change. By studying the isotope composition of water vapour and its dynamics, the researchers hope to improve the reliability of climate prediction models.

During the recent campaign, the team flew their research aircraft six times up to the altitude of 7km, collecting data using the ISOWAT diode laser spectrometer specially developed by the IMK for use on the research aircraft. This spectrometer ensures a high accuracy and temporal resolution under dry as well as under humid conditions.

The data was combined with those recorded by meteorological stations operated by the Spanish weather service (AEMET) at the altitude of 2370ft and 3550ft in the mountains of Tenerife and complemented with information acquired by the infrared instrument IASI (Infrared Atmospheric Sounding Interferometer) operated on board of the European METOP weather satellite.

“For this campaign, the IMK measurement methods for ground- and satellite-based remote sounding were combined with IMK’s aircraft-based in-situ measurement methods,” Schneider said. “We found good agreement between the datasets. This means that the precision of the remote sounding instruments, that is the quality of the data supplied by them, was confirmed.”

For the first time, the researchers have proved that both  the meteorological stations of the worldwide Network for the Detection of Atmospheric Composition Change and modern weather satellites provide reliable global data for the isotope composition of tropospheric water vapour.

Better understanding of the mechanisms associated with the atmospheric water budget based on isotope composition is the objective of the MUSICA project coordinated by Schneider at IMK. MUSICA, standing for Multi-platform Remote Sensing of Isotopologues for Investigating the Cycle of Atmospheric water, is funded by the European Research Council with a £1.25m grant.

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