TROPOS measurement campaign on small-scale variability of sunlight in the USA successfully concluded

Leipzig, 07.09.2023

important climate data at the Earth’s surface for the latest satellite generations and the energy transition.



Leipzig/ Oklahoma City. For the first time, German researchers have measured the influence of clouds on short-term fluctuations of solar radiation in North America. They have used a globally unique network of radiation sensors that was designed and built at the Leibniz Institute for Tropospheric Research (TROPOS), which has been deployed in the flat prairies of the Midwest of the USA from the beginning of June until the end of August this year. So-called pyranometers have recorded the incoming sunlight at 60 locations distributed over an area of 6x6 square kilometres in the US state of Oklahoma with second precision. The researchers from Leipzig  have measured in the direct vicinity of the Southern Great Plains (SGP) Atmospheric Observatory, the world's largest and most comprehensive observatory for atmospheric radiation. The "Small-Scale Variability of Solar Radiation" (S2VSR) measurement campaign by TROPOS, the US radiation measurement programme ARM, and the University of Oklahoma has successfully collected important climate data at the Earth surface. The planned scientific analysis of this data aims for a more efficient use of the latest generations of weather and environmental satellites and photovoltaic systems, and to make weather forecasts and climate models more accurate.


These measurements complement the data sets obtained during six previous field campaigns in Germany and in the Arctic since the construction of this network 10 years ago. For this campaign, not only the prevailing meteorological conditions are of interest, but also the extensive possibilities for comparison with routine measurements at the site of the observatory and in the entire state of Oklahoma, namely the comprehensive atmospheric measurements of the ARM programme and the Oklahoma MESONET. The TROPOS pyranometer network has supplemented these with information on fluctuations on the second and decameter scale, which the routine measurements cannot provide due to the too-large distances between stations. The data will now serve as a basis for comparisons with the latest satellite observations: on the one hand, with the American geostationary GOES-R satellite, which already provides observations with 500m resolution every 5 minutes, similar to those of the European METEOSAT satellites of the third generation expected for the end of this year; and on the other hand, with the European Sentinel-2 mission, with images of up to 10 metres spatial resolution.

The field campaign relied on the logistical support and very good cooperation with the American Atmospheric Radiation Measurement (ARM) programme. ARM is focused on the study of the atmosphere and its interactions with atmospheric radiation, and has operated the observatory in Oklahoma since 1992. Another important partner for the campaign and the planned scientific analysis of these observations is the School of Meteorology at the University of Oklahoma. It is the largest meteorology department in the United States and is traditionally better known for its severe weather research. But it has made a significant shift in the last 8 years to a broader atmospheric research programme. „The collaboration on the S2VSR measurement campaign offers excellent opportunities for our CL2EAR (CLouds ClimatE Aerosols Radiation) research group,” says Prof. Jens Redemann, Director of the School of Meteorology. „Through S2VSR, our students have gotten "hands-on" training in handling and data analysis of this unique network of pyranometers that could provide the key to many questions in our research field. We hope for a long and comprehensive collaboration between TROPOS and OU Meteorology.”

“During the 12-week campaign, two measurement stations were damaged by mowing activities, and only one could be repaired. In the course of the routine maintenance, occasional impairments of the measurements were found due to dirty or tilted pyranometers. However, the preliminary quality assurance of the collected data shows that the overall quality and availability is very high even in comparison to past campaigns, and that the campaign was a great success. Here, the commitment of the students of the University of Oklahoma for the maintenance needs to be emphasised in particular, ” reports Dr. Hartwig Deneke from TROPOS

The scientific analysis of the Small-Scale Variability of Solar Radiation (S2VSR) campaign data, which will now begin, will aim for new insights into the short-term fluctuation of sunlight at the Earth's surface as caused primarily by clouds. „On these scales, effects in atmospheric radiative transfer are dominated by the 3-dimensional structure of clouds, which so far is insufficiently taken into account by current weather and climate models as well as in satellite-based products. We hope that in the medium term, the gained insights will also contribute towards improving short-term forecasts of sunlight for the optimal use of renewable energy generated by photovoltaics,” explains Dr. Hartwig Deneke.




Contacts for media:


Dr. Hartwig Deneke

Leibniz Institute for Tropospheric Research (TROPOS), Leipzig

Phone: +49 341 2717-7168



Prof. Dr. Andreas Macke

Director and Head of the Department Remote Sensing of Atmospheric Processes , Leibniz Institute for Tropospheric Research (TROPOS), Leipzig

Phone: +49 341 2717-7060


as well as

Prof. Dr. Jens Redemann

Director of the School of Meteorology, University of Oklahoma



Tilo Arnhold, public relations, TROPOS

Phone: +49 341 2717-7189


Media Relations, University of Oklahoma

Phone: +1 (405) 325-1701

Email: OUnews[at]




Further information and links:



Blog: S2VSR


TROPOS Pyranometer network PyrNet


ARM campaign description for SGP2023S2VSR:


The Southern Great Plains (SGP) atmospheric observatory


The Oklahoma Mesonet


CLoud-CLimatE-Aerosol-Radiation (CL)2EAR research group in the School of Meteorology at the University of Oklahoma



Previous TROPOS press releases on the topic:


Clouds, Light & Shadow. Measurement campaign in Jülich records the spatial variability of solar radiation for the first time (press release, in German, 10.06.2013)


Researchers capture clouds. Large-scale measurement campaign in Jülich captures the spatial structure of the cloudy atmosphere with unprecedented accuracy (press release, in German, 18.03.2013)






The Leibniz Institute for Tropospheric Research (TROPOS) is a member of the Leibniz Association, which connects 97 independent research institutions that range in focus from the natural, engineering and environmental sciences via economics, spatial and social sciences to the humanities. Leibniz Institutes address issues of social, economic and ecological relevance. They conduct knowledge-driven and applied basic research, maintain scientific infrastructure and provide research-based services.

The Leibniz Association identifies focus areas for knowledge transfer to policy-makers, academia, business and the public. Leibniz institutions collaborate intensively with universities – in the form of “Leibniz ScienceCampi” (thematic partnerships between university and non-university research institutes), for example – as well as with industry and other partners at home and abroad.

They are subject to an independent evaluation procedure that is unparalleled in its transparency. Due to the importance of the institutions for the country as a whole, they are funded jointly by the Federation and the Länder, employing some 20,500 individuals, including 11,500 researchers.

The entire budget of all the institutes is approximately 2 billion euros. They are financed jointly by the Federal Government and the Länder. The basic funding of the Leibniz Institute for Tropospheric Research (TROPOS) is therefore financed by the Federal Ministry of Education and Research (BMBF) and the Saxon State Ministry of Science and the Arts (SMWK). The Institute is co-financed with tax revenues on the basis of the budget approved by the Saxon State Parliament.



The PyrNet devices from TROPOS measured global radiation, temperature and humidity every second in the fields of Oklahoma over the next 3 months. Photo: Jonas Witthuhn, TROPOS

Colleagues from the University of Oklahoma also helped with the installation of the PyrNet. Photo: Jonas Witthuhn, TROPOS

During installation, the devices must be precisely aligned to provide reliable data. Photo: Jonas Witthuhn, TROPOS