Andreas Christen

We advertise a funded PhD position (3.5 years) as part of our new Excellence Cluster "Future Forests" at @uni-freiburg.de. Great opportunity to work on forest microclimates and sensor networks in my group and with @mixedforests.bsky.social Apply by January 12, 2026: uni-freiburg.de/en/job/00004...

In summer 2026, the hottest summer on record for Western Europe, ICOS stations measured the same conditions they operated through. The stations offer a rare perspective on climate extremes: they both operate through them and measure how the carbon cycle responds. 🔄🌍 👉 https://ow.ly/OVyI50ZSAN8

Our new open-access paper in "Landscape and Urban Planning" showcases how new AI-driven urban climate tools can support climate adaptation planning in cities. Using a case neighborhood we explore the potential of AI tools for balancing greening, density and heat exposure. doi.org/10.1016/j.la...

In our ECOSENSE forest we are monitoring ecosystem processes and stresses in real-time using distributed sensor networks: Our new @egu.eu preprint discusses the implementation of this major technical infrastructure and its data management @ecosense-sfb-1537.bsky.social - doi.org/10.5194/egus...

Is satellite land surface temperature (LST) a good proxy for urban heat stress? In our new article led by Ferdinand Briegel @kit.edu and @uni-freiburg.de in RSE we conclude "no" - comparing nearly 100 LST scenes to detailed 1-m heat stress modelling at pedestrian level. doi.org/10.1016/j.rs...

Summer 2025 was unusually warm and wet. At our at Hartheim @icos-ri.eu station of @uni-freiburg.de in the Upper Rhine Valley JJA was 1°C warmer and +25% precipitation vs. 1991–2020 (June +2.7°C). Only 4 years since 1978 were both wetter and warmer, but 2025 stands out as most extreme yet.

#Hitzebelastung der Zukunft prognostiziert: Forschende von #UniversitätFreiburg und Karlsruher Institut für Technologie @kit.edu haben KI-Modell entwickelt, das städtischen Hitzestress für ganze Stadtgebiete über mehrere Jahrzehnte hinweg simulieren kann. ufr.link/hitzeprognose @envmet.bsky.social

In a paper just published in "Urban Climate" we describe and assess a new machine-learning algorithm for gap-filling urban weather station networks. We use this to construct maps of annual climate statistics - code and paper are open access #I4C #urbisphere www.sciencedirect.com/science/arti...

Years of drought turn forest into source of CO₂ - Press release on our research with @simonhaber.bsky.social and @chriswernerlab.bsky.social at @icos-ri.eu site DE-Har, showing tree mortality following droughts has fundamentally shifted forest structure & functioning uni-freiburg.de/en/years-of-...

Great presence of @icos-ri.eu at the International Conference on Urban Climate (#ICUC12) today in Rotterdam. Presenting latest science on modelling, observing, and attributing urban greenhouse gas emission reductions using ICOS infrastructure in Paris, Munich, Zurich Berlin, Heidelberg & Heraklion.

Today was another unusually hot day in Freiburg, with temperatures above 38°C. Our urban weather station network operated by @uni-freiburg.de and funded by @erc.europa.eu reveals intra-urban differences and where it was coolest (in a forest). Explore the map weather.uni-freiburg.de/map/freiburg...

During the current #UKHeatWave we measured for the first time a #TropicalNight across our Bristol street-level weather network. Stations outside the city and on hills cooled down to < 20°C while the urban heat island kept the city core above 20°C last night. weather.uni-freiburg.de/map/bristol/...

By combining ecophysiological, satellite, and ‪‬eddy covariance data we show how our @icos-ri.eu forest ecosystem changes in function and structure following hot-drought-induced tree mortality. New article by @simonhaber.bsky.social as part of @ecosense-sfb-1537.bsky.social doi.org/10.1111/plb....

New weather stations on lamp-posts across Bristol, UK reveal interacting urban, orographic and coastal effects in real time. Last night, we observed an urban heat island of 5ºC. Multi-institutional effort between urbisphere ‪@erc.europa.eu‬, @urbanair.bsky.social‬ and ASSURE: doi.org/10.5281/zeno...

Celebrating our successful new excellence cluster #FutureForests @uni-freiburg.de. Thanks @dfg.de, this will enable us to substantially invest in exciting and much-needed research for the next 7 years - predicting and transforming forest systems in a changing climate uni-freiburg.de/futureforest...

Using high-resolution weather models and a network of 25 LiDAR-ceilometers over Berlin, Germany, we explore how large cities modify the atmospheric boundary layer. New preprint on collaborative work by @uniofreading.bsky.social‬, @metoffice.bsky.social‬ and @uni-freiburg.de doi.org/10.5194/egus...

Can you spot the dead Pine trees? If you are interested to learn more about legacy effects in this ecosystem, join me for my talk @egu.eu this afternoon: meetingorganizer.copernicus.org/EGU25/EGU25-... @ecosense-sfb-1537.bsky.social @envmet.bsky.social @chriswernerlab.bsky.social

Impressive time-lapse of leaf emergence during the last weeks recorded by phenocams at our research forest @uni-freiburg.de. In the @dfg.de funded @ecosense-sfb-1537.bsky.social we study forest ecosystem functioning, and species interactions with novel sensor technologies uni-freiburg.de/ecosense/

New preprint on our harmonised wind dataset from 6 doppler wind lidars operated along a transect through Paris, France. This data supports urban weather and climate modeling in multiple @erc.europa.eu, @wmo-global.bsky.social, @icos-ri.eu and @horizoneu.bsky.social projects: doi.org/10.5194/essd...

At the #UrbanGHGsummit in Geneva, greenhouse gas emission experts from #ICOSCities project are joining forces to curb urban emissions. Leena Järvi, Olivier Laurent, and Andreas Christen are presenting the latest findings from the project. @helsinki.fi @envmet.bsky.social @lsce-ipsl.bsky.social

Andreas Christen @envmet.bsky.social from University of Freiburg presenting an overview of the principles, applications and limitations of eddy covariance flux measurements in cities. This is part of the Urban Good Practice Guidelines and will be discussed more this week #UrbanGHGsummit #ICOSCities

Our new paper with @ubcgeography.bsky.social in Agric. For. Meteorol. investigates climatic sensitivity of evapotranspiration in an ombrotrophic bog on Canada's West Coast. The bog's water balance will be most sensitive to future increases in summer vapour pressure deficit. doi.org/10.1016/j.ag...

New preprint at @egu.eu on greenhouse gas emission measurements from cities as part of @icos-ri.eu. Our group @uni-freiburg.de and partners propose a new method for attributing emissions to sources using multi-species eddy fluxes on a tall tower over Zurich. egusphere.copernicus.org/preprints/20...

An arcus cloud passed over Freiburg earlier this evening. It was part of a convective system embedded in a cold front. A sharp increase in wind, a drop in air temperature and an unusual pressure jump +2 hPa in just 5 minutes measured @uni-freiburg.de weather station.

We advertise a new Full Professorship (W3) in Fire Ecology @uni-freiburg.de. Do you work on effects of fires on vegetation biodiversity, functionality, dynamics and fire mitigation? Consider applying to join our vibrant Faculty of Environment and Natural Resources. uni-freiburg.de/en/job/00004...

Urban Heat Islands are usually associated with heatwaves in summer. But during cold winter nights, they are equally present. Our street-level network @uni-freiburg.de reveals that frost is less likely to occur in the city of Freiburg (24 days per year) compared to the rural surrounding (50-60 days).

“Scientists brace ‘for the worst’ as Trump purges climate mentions from websites” by Oliver Milman for The Guardian. Read more here: www.theguardian.com/us-news/2025...

Our new paper in "Ecohydrology" led by @simonhaber.bsky.social describes dynamics of short-term droughts on tree water potentials. We were using new continuous stem water sensors at our @icos-ri.eu site in Hartheim @uni-freiburg.de as part of @ecosense-sfb-1537.bsky.social doi.org/10.1002/eco....

New @eurogeosciences.bsky.social preprint on our @icos-ri.eu relaxed eddy accumulation system for measuring 14C fluxes. Developed by @uni-freiburg.de, @uniheidelberg.bsky.social and @maxplanck.de, it aims to partition city emissions into fossil fuel and biogenic contributions doi.org/10.5194/egus...

Field trip with @uni-freiburg.de students to learn about urban climate activities in Basel - Meteoblue.com showcased their city climate services and city wide sensor networks. At @unibas.ch we learned how eddy covariance on towers is used to monitor GHG emission reductions.

New article in "Sustainable Cities and Society" documents custom-built weather stations to monitor pedestrian-level thermal comfort on street lights. They are part of our city-wide sensor network @uni-freiburg.de to evaluate urban climate models - funded by ERC @ec.europa.eu doi.org/10.1016/j.sc...

Our new article in @eurogeosciences.bsky.social Geoscientific Instrumentation - How meteorological data streams from diverse instruments, scales, and campaigns are integrated in a data management approach to support urban climate modelling @suegrimmond.bsky.social gi.copernicus.org/articles/13/...

Honored to receive FLUXNET 2024 Paper of the Year award! Greatly appreciate the recognition of our flux work in BC Canada. A heartfelt thank you to everyone who supported me (Andy, Paul, and many more). #AGU2024 #AGU24 (pc: Sara Knox)

Our new paper in Urban Climate presents a machine-learning approach to simulate airflow in real urban canopies based on large eddy simulations. Result from recent #I4C project on AI applications in environmental research and collaboration between @unifreiburg and Columbia U. doi.org/10.1016/j.uc...

Job: DWL/LAS analysis with NWP jobs.reading.ac.uk/Job/JobDetai... Recent papers relevant to this: doi.org/10.1175/BAMS... doi.org/10.1002/qj.4... doi.org/10.1002/qj.4... Work with the MO/ECMWF/ERC urbisphere /NERC ASSURE at University of Reading. Closing date: 11/12/2024