Tobias Gerken

Understanding Atmosphere & Environment -One Ecosystem at a Time-

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New paper: Land-atmosphere feedbacks and information flows

This was a fun paper to do. It is nice to explore some new and innovative methods to understand and quantify land-atmosphere feedback: Information Flows.

We can use the wealth of FLUXNET data to find hotspots of coupling. 

Citation:  Gerken, T., Ruddell, B.L., Yu, R., Stoy, P.C., Drewry, D.T., 2019. Robust observations of land-to-atmosphere feedbacks using the information flows of FLUXNET. npj Climate and Atmospheric Science 2, 37. https://doi.org/10.1038/s41612-019-0094-4  

Editorial Summary

“Big data” methods reveal robust hotspots of land–atmosphere coupling. Sparse observations and inadequate analytical tools have hindered our understanding of land–atmosphere feedbacks, including the exchange of energy, water, and CO2. Emergent methods such as machine learning, however, offer new opportunities, as Tobias Gerken from Montana State University, USA, and colleagues, demonstrate. A “big data” approach is adopted to characterise the spatial and temporal variability of land–atmosphere coupling without a priori assumptions: information flows are computed from 251 FLUXNET sites which are subsequently used to train a neural network. Distinct regional differences in the magnitude of land–atmosphere feedbacks are found, related to climatic zone and biome type; coupling in semi-arid ecosystems, for example, are strongly related to seasonal water availability. Complementing model studies with such empirical approaches may assist in quantifying climate change impacts on ecosystem services.

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New paper: Climate trends in the Northern Great Plains

Huge congratulations to Gabe Bromley for publishing the first paper of his PhD work.

Lots of hard work went into documenting recent climate trends in the North American Great Plains that are associated with a more moist environment.

This paper will provide an excellent basis for his further investigation of water sources for the moistening and the role of land management.

Citation:  Bromley, G.T., Gerken, T., Prein, A.F., Stoy, P.C., 2019. Recent trends in the near-surface climatology of the northern North American Great Plains. J. Climate. https://doi.org/10.1175/JCLI-D-19-0106.1  

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New paper: Ecosystem evaporation-transpiration partitioning

Evaporation and transpiration are measure together as evapotranspiration on the ecosystem scale. But as transpiration is strongly linked to photosynthesis and plant stomatal activity, it will respond differently to environmental change than evaporation from soils, which is a purely physical process.

Citation: Stoy, P. C., El-Madany, T. S., Fisher, J. B., Gentine, P., Gerken, T., Good, S. P., Klosterhalfen, A., Liu, S., Miralles, D. G., Perez-Priego, O., Rigden, A. J., Skaggs, T. H., Wohlfahrt, G., Anderson, R. G., Coenders-Gerrits, A. M. J., Jung, M., Maes, W. H., Mammarella, I., Mauder, M., Migliavacca, M., Nelson, J. A., Poyatos, R., Reichstein, M., Scott, R. L., and Wolf, S.: Reviews and syntheses: Turning the challenges of partitioning ecosystem evaporation and transpiration into opportunities, Biogeosciences, 16, 3747–3775, https://doi.org/10.5194/bg-16-3747-2019, 2019.    

In our review, which I was glad to contribute to, we explore ways forward in estimating evaporation and transpiration separately.                

The abstract is found below:

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New Paper: Interannual variability on global net carbon ecosystem exchange

Dr. Zheng Fu published a new paper on how interannual variability of maximum ecosystem carbon shapes the total variability of ecosystem carbon exchange.

His research helps us to better understand which global regions are more sensitive to disturbances during the growing season (e.g. drought) compared to the total length of the growing season.

I am glad that I was able to contribute.

Citation: Fu, Z., Stoy, P.C., Poulter, B., Gerken, T., Zhang, Z., Wakbulcho, G., Niu, S., 2019. Maximum carbon uptake rate dominates the interannual variability of global net ecosystem exchange. Global Change Biology. https://doi.org/10.1111/gcb.14731  

The plain text summary is found below:

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The Pulse of the City - Berlin

A few days ago, I started experimenting with Foursquare’s API to explore Berlin’s neighborhoods and its dynamic life and to capture the pulse of the city.

I used Foursquare’s trending functionality to retrieve trending venues for the whole city over the course of 5 days in April.

We can see Berlin’s pulse in the animation below, with lots of activity during the day and relative quiet during the night.

As we can expect, transit venues like Airports and Train Stations are consistently trending, while Events and Outdoor spaces are picking up on the weekend.

Foursquare also returned a few trending venues that were surprising.

For example, Foursquare returned an Assisted Living facility as trending during Saturday and Sunday.

A closer look reveals, that the venue name rp19wg is actually associated with the re:publica 2019 digital society convention that was held in Berlin during May 6 - 8, which also explains, why Meetings are trending.

Given that re:publica 2019‘s nature as a convention of digital natives and the relative absence of Nightlife venues, Berlin is famous for, in the trending data-set, we can certainly ask the question whether the Foursquare data-set really captures the whole picture or whether it is skewed towards media-savvy people with large digital footprints.  

On a personal note, it is nice to see that Curry 36 - my neighborhood curry-wurst joint during my time in Berlin - is doing were well and still a favorite on a Friday night.

The complete analysis, done as part of IBM’s Data Science Professional Certificate on Coursera, can be found on my GitHub.

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My Research Network

Penn State subscribes to Pure, Elsevier’s Research Management suite.

It provides a great visualization of my research network: It is nice to see all my research connections in one place:

On a personal level, we can clearly make out two clusters, one being my PhD work with Hans-F Graf (Cambridge) and Thomas Foken (Bayreuth) on the Tibetan Plateau and on the other branch my later work on the Brazilian Amazon (with Jose D. Fuentes and Marcelo Chamecki) and the U.S. Northern Great Plains (with Paul Stoy).

I have been truly fortunate to work with this many great people!

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Human encroachment alters air quality in Amazon rainforest

A huge shout-out to Dr. Dandan Wei. Not only did she graduate with her PhD last weekend, but her research was also featured by Penn State and then at EurekAlert.

The paper (previously featured here), with contains a lot of nice results, can found here:

Citation: Wei, D; Fuentes, JD; Gerken, T; Trowbridge, AM; Stoy, PC; Chamecki, M: Influences of nitrogen oxides and isoprene on ozone-temperature relationships in the Amazon rain forest, Atmospheric Environment, 206, 280-292, doi: 10.1016/j.atmosenv.2019.02.044 (2019)

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Undergraduate forecaster position

We are looking for two student forecasters, who are interested in contributing to a NASA funded project.

Description:

Two Undergraduate Forecaster positions are available to support the NASA-funded ACT­ America airborne research project (https://www-air.larc.nasa.gov/missions/ACT­ America/index.html). The student Forecasters will prepare and deliver weather forecasts in support of the summer 2019 ACT-America research flight campaign. Additional work gathering, quality checking, and archiving weather and flight research data associated with the flight campaign may also be needed. The positions are available for the summer of 2019. Students majoring in Meteorology and Atmospheric Science with interests in forecasting in a field campaign environment are encouraged to apply. Interested candidates may contact Prof. Ken Davis ([email protected]) and/or Prof. Tobias Gerken ([email protected]) for more information. Applicants should upload a cover letter explaining their interest in the position, a resume including the names and contact information for 2 references, and an academic transcript. Review of applications will begin April 1 and will be ongoing until suitable candidates are found. 

https://psu.jobs/job/86229

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Discussion Paper: Evapotranspiration Partitioning

Partitioning measured total evapotranspiration into transpiration from plants and evaporation from soils is really important as evaporation and transpiration will respond differently in a changing climate.

Our new paper submitted to Biogeosciences outlines some of the challenges and opportunities.

Citation: Stoy, P. C., El-Madany, T., Fisher, J. B., Gentine, P., Gerken, T., Good, S. P., Liu, S., Miralles, D. G., Perez-Priego, O., Skaggs, T. H., Wohlfahrt, G., Anderson, R. G., Jung, M., Maes, W. H., Mammarella, I., Mauder, M., Migliavacca, M., Nelson, J. A., Poyatos, R., Reichstein, M., Scott, R. L., and Wolf, S.: Reviews and syntheses: Turning the challenges of partitioning ecosystem evaporation and transpiration into opportunities, Biogeosciences Discuss.,   https://doi.org/10.5194/bg-2019-85, in review, 2019.        

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Paper: Nitrogen Oxides and Isoprene Impacts on Air Chemistry in Amazonia

Congratulations to freshly minted PhD (and now postdoc) Dandan Wei on her new paper! Its a great follow-up to her previous work.

Some really nice results on interactions between pollution from a tropical Megacity and an isoprene emitting rain forest.

Citation: Wei, D; Fuentes, JD; Gerken, T; Trowbridge, AM; Stoy, PC; Chamecki, M: Influences of nitrogen oxides and isoprene on ozone-temperature relationships in the Amazon rain forest, Atmospheric Environment, in press, doi: 10.1016/j.atmosenv.2019.02.044 (2019)

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New project: Atmospheric Carbon & Transport - America

With 2019 ahead, I have started a new position as Penn State as part of the NASA funded Atmospheric Carbon & Transport project (ACT-America).

Credit: ACT-America

ACT-America is a research project that aims at improve regional, seasonal estimates of CO2 and CH4 sources and sinks in the United States by reducing the transport uncertainty of atmospheric inversion models (inversion models are models that use measurements of atmospheric gas concentrations to estimate corresponding sources and sinks).

To do so, the project conducts high resolution atmospheric transport modeling in conjunction with air craft campaigns that measure CO2 and CH4 concentrations across the western US.

One of the nice things about contributing to NASA projects is the fact that you get to have a mission patch:

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Paper: Surface-atmosphere exchange of carbon dioxide in tropical rainforests

Our new paper on the dynamics of CO2 surface-atmosphere exchange in tropical rainforests was published today.

A great thanks to Zheng, who took the lead on this nice paper!

Citation: Fu, Z., Gerken, T., Bromley, G., Araújo, A., Bonal, D., Burban, B., Ficklin, D., Fuentes, J.D., Goulden, M., Hirano, T., Kosugi, Y., Liddell, M., Nicolini, G., Niu, S., Roupsard, O., Stefani, P., Mi, C., Tofte, Z., Xiao, J., Valentini, R., Wolf, S., Stoy, P.C., 2018. The surface-atmosphere exchange of carbon dioxide in tropical rainforests: Sensitivity to environmental drivers and flux measurement methodology. Agricultural and Forest Meteorology 263, 292–307. https://doi.org/10.1016/j.agrformet.2018.09.001  

Global repositories of environmental data such as FLUXNET have become such an important tool to study global and regional ecosystem dynamics and to assemble a comprehensive view of ecosystem and climate processes. At the same time, there are many challenges as observation sites in remote regions are difficult to maintain, which impacts data availability and quality.

We really need to fund these networks to collect representative data!

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News story: Let it Rain

A while ago, Paul Stoy and I were interviewed by The Furrrow, which is published by the agricultural equipment maker John Deere and distributed to agricultural producers around the globe.

The story Let it Rain is a wonderful example of communicating science to an audience, where it really matters:

Image: Screenshot of https://www.johndeerefurrow.com/2018/06/04/let-it-rain/

We were originally contacted, because they were working on a story about rain in the Great Plains and saw coverage of our research on Massive.com.

I think The Furrow’s writers did a great job of summarizing different aspects of rain, drought, and soil health, while directly reporting what climate and agricultural scientists have to say.

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Environmental Data Science

A recent article (Big Data Goes Green) on Nature.com got me thinking about Environmental Data Science.

The proliferation and availability of climate mode data, Earth observations, station data, and global reanalysis together with advances in machine learning techniques really allows for new ways of understanding ecosystem processes.

One example, I have been working on is trying to better understand land-atmosphere interactions and to identify regions where feedbacks between land and atmosphere are strong.

For example, we used an artificial neural network to create global maps of how the turbulent exchange of heat influences clouds.

Figure: Land-atmosphere coupling strength T(H>Rg) between surface sensible heat flux (H) and incoming solar radiation (Rg; a proxy for clouds). Reddish colors indicate stronger couplings.

Below the hood, we used data from more than 250 FLUXNET stations to extrapolate the land-atmosphere coupling relationship across the globe. For this we also used Modis satellite observations of vegetation and gridded weather data. Its really nice that all these data are provided to the scientific community for free courtesy of NASA and the Department of Energy, who fund these endeavors.

The results look really neat and point to strong feedbacks in semi-arid regions, which are particularly vulnerable to global environmental change.

In the coming weeks, I will be writing about some of the tools I use for environmental data science and why I think they are useful:

Matlab and Toolbooxes

Python (Scipy)

Jupyter Notebook

Git & Github

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Paper on Kobresia pastures of Tibet

It has been a while since I worked on biosphere atmosphere interactions on the Tibetan Plateau as part of TIP. It was a real pleasure doing a PhD in such an interdisciplinary project, that included ecology, hydrology, atmospheric sciences, and so much more.

A few days ago, a review paper on the Tibetan Kobresia pygmaea ecosystem was published. I contributed some information on the ecosystems impact on land-atmosphere interactions and surface energy balance.

Citation:  Miehe, G., Schleuss, P.-M., Seeber, E., Babel, W., Biermann, T., Braendle, M., Chen, F., Coners, H., Foken, T., Gerken, T., Graf, H.-F., Guggenberger, G., Hafner, S., Holzapfel, M., Ingrisch, J., Kuzyakov, Y., Lai, Z., Lehnert, L., Leuschner, C., Li, X., Liu, J., Liu, S., Ma, Y., Miehe, S., Mosbrugger, V., Noltie, H.J., Schmidt, J., Spielvogel, S., Unteregelsbacher, S., Wang, Y., Willinghöfer, S., Xu, X., Yang, Y., Zhang, S., Opgenoorth, L., Wesche, K., 2019. The Kobresia pygmaea ecosystem of the Tibetan highlands – Origin, functioning and degradation of the world’s largest pastoral alpine ecosystem: Kobresia pastures of Tibet. Science of The Total Environment 648, 754–771. https://doi.org/10.1016/j.scitotenv.2018.08.164 (open access)  

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New paper: Convective suppression and drought in Montana

Our new paper on land-atmosphere interactions that affected the development of the 2017 flash drought in Montana and the Dakotas is out now.

Plain text summary: An unprecedented flash drought took place across parts of the US Northern Great Plains and Canadian Prairie Provinces during the summer of 2017 that in some areas was the worst in recorded history. We show that this drought was preceded by a breakdown of land–atmosphere coupling, reducing the likelihood of convective precipitation. It may be useful to monitor land–atmosphere coupling to track and potentially forecast drought development.

Citation: Gerken, T., Bromley, G. T., Ruddell, B. L., Williams, S., and Stoy, P. C.: Convective suppression before and during the United States Northern Great Plains flash drought of 2017, Hydrol. Earth Syst. Sci., 22, 4155-4163, https://doi.org/10.5194/hess-22-4155-2018, 2018.    

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Python webscraping

It is summer and I finally have some time to try something new. I decided learn how to use Python for reading data from webpages. I saw a similar exercise on Randy Chase’s (one of my former summer undergraduate students) webpage at Illinois.

I know that using API’s is typically better, and learning to better use the Weather Service API comes next.

But for now, I am using BeatifulSoap to read some data from the National Weather Service, to create a graph of current and forecast weather. 

Here is an example for Charlottesville (KCHO):

Next, I will start running this script on a web-server to keep it up to date and maybe make the graphs a bit more beautiful.

The full code can be found on my GitHub.

Update: An updated nicer version of the same plot, which rain in the last 24 hours: