Image of the Month

Methane anomalies in Greenland

Methane (CH4) represents the second most important greenhouse gas after carbon-dioxide (CO2) and is roughly 28-times more potent than CO2. It is released through human activities (agriculture, waste, fossil fuels,...) and natural processes, for example bio-chemical processes in wetlands or in thawing permafrost.

That is why we are investigating the atmospheric methane concentration (XCH4) within the framework of the junior-research group „Greenhouse gases in the Arctic“ using satellite data. Over Greenland strong methane anomalies could be observed (Fig. 1a), i.e. regions with very high or low concentrations. However these anomalies are not related to emissions from the permafrost but to inaccuracies in the digital elevation model (DEM) used in the calculations (Fig. 2), as our research has shown.
In addition to Greenland further regions show inaccuracies in older DEMs (Fig. 3). Following this finding a more recent DEM was implemented for the WFMD methane product which is developed at the IUP. The anomalies vanish in the new product both for Greenland (Fig 1b) and the other regions which improved the general quality of the product.



Reference:

Hachmeister, J., Schneising, O., Buchwitz, M., Lorente, A., Borsdorff, T., Burrows, J. P., Notholt, J., and Buschmann, M.: On the influence of underlying elevation data on Sentinel-5 Precursor TROPOMI satellite methane retrievals over Greenland, Atmos. Meas. Tech., 15, 4063–4074, https://doi.org/10.5194/amt-15-4063-2022, 2022.

Contact:
jonas_h@iup.physik.uni-bremen.de

Future changes in droughts in the CMIP5 ensemble analyzed with the Earth System Model Evaluation Tool (ESMValTool)

Motivated by the dry summer of this year, our image of the month shows projections of future changes in number, duration, average standard precipitation index (SPI), and severity of droughts as simulated by the climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) in the RCP8.5 future scenario. The SPI describes local precipitation anomalies and can be used to identify meteorological droughts. By the end of the 21stcentury the projections show an increase of drought number, duration and severity mainly in the already dry, subtropical areas. A shift towards more frequent droughts is found for most parts of the globe for drought indices which in addition to precipitation consider the potential evapotranspiration, like the Standardized Precipitation Evapotranspiration Index (SPEI) or are based on water balance calculation, like the scaled Palmer Drought Severity Index (SC-PDSI), see e.g. Ruhe (2022).

The diagnostics to produce this figure were processed with the Earth System Model Evaluation Tool (ESMValTool), a community diagnostics and performance metrics tool designed to improve comprehensive and routine evaluation of Earth System Models (ESMs). It provides a highly optimized preprocessor written in Python (Righi et al. 2020) centralizing standard operations on input data such as regridding or computation of multi-model statistics to allow for efficient and user-friendly data processing. A large number of diagnostics is provided with the ESMValTool, covering quasi-operational and comprehensive evaluation of ESMs, like the calculation and plotting of mean state, trends, and variability for atmospheric, oceanic, and terrestrial variables (Eyring et al. 2020), as well as diagnostics for emergent constraints and analysis of future projections from ESMs in CMIP (Lauer et al. 2020). Our image of the month is the result of an ESMValTool recipe (recipe_martin18grl.yml) that has been implemented in the ESMValTool version 2.0 and publishedin Weigel et al. (2020) that summarizes diagnostics for extreme events, regional and impact evaluation.

References

Eyring, V., Bock, L., Lauer, A., Righi, M., Schlund, M., Andela, B., Arnone, E., Bellprat, O., Brötz, B., Caron, L.-P., Carvalhais, N., Cionni, I., Cortesi, N., Crezee, B., Davin, E.L., Davini, P., Debeire, K., de Mora, L., Deser, C., Docquier, D., Earnshaw, P., Ehbrecht, C., Gier, B.K., Gonzalez-Reviriego, N., Goodman, P., Hagemann, S., Hardiman, S., Hassler, B., Hunter, A., Kadow, C., Kindermann, S., Koirala, S., Koldunov, N., Lejeune, Q., Lembo, V., Lovato, T., Lucarini, V., Massonnet, F., Müller, B., Pandde, A., Pérez-Zanón, N., Phillips, A., Predoi, V., Russell, J., Sellar, A., Serva, F., Stacke, T., Swaminathan, R., Torralba, V., Vegas-Regidor, J., von Hardenberg, J., Weigel, K., & Zimmermann, K.: Earth System Model Evaluation Tool (ESMValTool) v2.0 – an extended set of large-scale diagnostics for quasi-operational and comprehensive evaluation of Earth system models in CMIP. Geoscientific Model Development, 13, 3383-3438, 2020.

Lauer, A., Eyring, V., Bellprat, O., Bock, L., Gier, B.K., Hunter, A., Lorenz, R., Pérez-Zanón, N., Righi, M., Schlund, M., Senftleben, D., Weigel, K., & Zechlau, S.: Earth System Model Evaluation Tool (ESMValTool) v2.0 – diagnostics for emergent constraints and future projections from Earth system models in CMIP. Geoscientific Model Development, 13, 4205-4228, 2020.
Righi, M., Andela, B., Eyring, V., Lauer, A., Predoi, V., Schlund, M., Vegas-Regidor, J., Bock, L., Brötz, B., de Mora, L., Diblen, F., Dreyer, L., Drost, N., Earnshaw, P., Hassler, B., Koldunov, N., Little, B., Loosveldt Tomas, S., & Zimmermann, K.: Earth System Model Evaluation Tool (ESMValTool) v2.0 – technical overview. Geosci. Model Dev., 13, 1179-1199, 2020.

Ruhe, L.: A Comparison of Drought Indices in CMIP6 Climate Projections, M.Sc. Thesis, University of Bremen, Bremen, Germany, https://www.iup.uni-bremen.de/PEP_master_thesis/thesis_2022/Ruhe_MScThesis_2022.pdf, 2022.

Weigel, K., Bock, L., Gier, B. K., Lauer, A., Righi, M., Schlund, M., Adeniyi, K., Andela, B., Arnone, E., Berg, P., Caron, L.-P., Cionni, I., Corti, S., Drost, N., Hunter, A., Lledó, L., Mohr, C. W., Paçal, A., Pérez-Zanón, N., Predoi, V., Sandstad, M., Sillmann, J., Sterl, A., Vegas-Regidor, J., von Hardenberg, J., and Eyring, V.: Earth System Model Evaluation Tool (ESMValTool) v2.0 – diagnostics for extreme events, regional and impact evaluation, and analysis of Earth system models in CMIP, Geosci. Model Dev., 14, 3159–3184, https://doi.org/10.5194/gmd-14-3159-2021, 2021.

Links

ESMValTool Website: https://www.esmvaltool.org/
Software: https://github.com/ESMValGroup/ESMValTool
Dokumentation: https://docs.esmvaltool.org/
Tutorial: https://esmvalgroup.github.io/ESMValTool_Tutorial

Melt ponds are puddles of surface melt water that form on the Arctic sea ice during summer. They reduce the reflectivity and albedo of the surface and thus increase the energy absorption of incoming solar radiation. This self-enhancing process is called ice-albedo feedback and plays a significant role for the amplified warming of the Arctic compared to the mid-latitudes.

The polar remote sensing group at IUP works on a retrieval that extracts surface albedo and melt pond fraction from optical satellite measurements (https://seaice.uni-bremen.de/melt-ponds/). In the past two months we were on a RV Polarstern expedition in the Arctic (https://follow-polarstern.awi.de/?lang=en) to collect important in-situ data that will help to improve the forward model in the satellite retrieval. With a hyperspectral camera, called WALL-E, detailed spectra of melt pond and ice surfaces were measured to investigate their variability and evolution. Because of the spatial extension of the measurements also an estimate of the melt pond fraction is possible. To determine the driving forces of albedo change, these measurements were repeated on the same ice floes three times between 15th and 31st July 2022 (visit 1 to 3). The ice floe got “darker” during this time period (from 0.59 to 0.43 reflectance), which is mainly due to the increase of melt pond fraction but also a reduced reflectance of the ice surface (see bar plot in upper right).

Contact:
Dr. Gunnar Spreen(gunnar.spreen@uni-bremen.de)
Hannah Niehaus (niehaus@uni-bremen.de)

Global satellite maps of N2O from GOSAT-2

Nitrous oxide (N2O) is after carbon dioxide (CO2) and methane (CH4) the most important anthropogenic greenhouse gas. N2O is mainly produced by natural processes (e.g. by bacteria), but is also released in agriculture (fertilisers) and biomass burning processes. Although the atmospheric concentration of N2O is about 1000 times smaller than for CO2, the global warming potential of N2O is almost 300 times larger, which makes it a relevant contributor to climate change.

However, global measurements of N2O especially from satellites are sparse. The map in the image (from Noël et. al, 2022) shows the atmospheric distribution of XN2O (i.e. the total dry column average N2O) in April 2019 derived at IUP from measurements of the Japanese GOSAT-2 satellite.

As can be seen, total column concentrations of N2O are larger in the tropics than at higher latitudes. This is because most of the N2O is produced and located in the lower atmosphere, the troposphere, which reaches higher in the tropics.

Reference:

Noël et al., Retrieval of greenhouse gases from GOSAT and GOSAT-2 using the FOCAL algorithm, Atmos. Meas. Tech., 15(11), 3401–3437, 2022, doi: rm10.5194/amt-15-3401-2022.
https://amt.copernicus.org/articles/15/3401/2022/

Contact:

Stefan Noël (stefan.noel@iup.physik.uni-bremen.de)

A recent study conducted by the IUP "Cloud Aerosol Surface PArameter Retrieval" group as part of the Transregio (AC)³ investigates clouds, their properties, and the magnitude of the radiative effect of clouds in the Arctic based on satellite data.

Arctic clouds are an important factor in influencing Arctic climate. They have both warming and cooling effects. The reasons whether they warm or cool depend on different conditions. These include the microphysical properties of the clouds, the illumination, the thermodynamic phase of the clouds (i.e., to what degree they contain liquid or frozen water), and the reflectivity of the ground.

Although when viewed over the entire Arctic the cloudiness has not changed appreciably over time, some cloud properties have. For example, the optical thickness of liquid water clouds and that of pure ice clouds. Partially significant changes in cloud brightness (cloud albedo) are also obvious.


Reference: The aerosol, cloud and surface property group "Pan-Arctic and regional trends of reflectance, clouds and fluxes: implications for Arctic Amplification" (2022)

Kontakt/contact: Marco Vountas vountas@iup.physik.uni-bremen.de
or Luca Lelli luca@iup.physik.uni-bremen.de

https://www.iup.uni-bremen.de/aerosol

New measurement suite to improve Greenhouse Gases observations from aircraft,
University Bremen, Institute of Environmental Physics

Scientists at the Institute of Environmental Physics are specialised in the development and deployment of various types of airborne sensors to locate and quantify emissions of anthropogenic greenhouse gases by measuring atmospheric Methane (CH4) and Carbon dioxide (CO2) distributions. To accurately estimate emissions from those distributions, precise knowledge of the local wind field is necessary. Therefore, in spring 2022, a newly acquired 5-hole turbulence probe together with a in-situ greenhouse gas analyser, were successfully mounted in one of the wing pods of the motor glider of Jade Hochschule Wilhelmshaven. The Diamond HK36TTC-ECO is a flexible platform for different remote sensing tasks, as it needs no certification process to install sensors. First test flights in cooperation with Jade Hochschule Wilhelmshaven were successfully conducted in northern Germany to calibrate the new instrument. Additionally, fly-bys at the ICOS measurement tower in Steinkimmen/Ganderkesee operated by the German Weather Service DWD, which observes the vertical wind profile at 5 different altitudes till an altitude of 250m, were carried out. Those measurements are used for comparisons and will improve the calibration quality of the wind probe further. Additional, calibration flights comparing measurements from airborne, LIDAR, drone, and tower measurements are planned.

Contact: heinrich.bovensmann@uni-bremen.de

TROPOMI-retrieved underwater light attenuation in three spectral regions in the ultraviolet to blue. Frontiers in Marine Science 9: 787992. doi:10.3389/fmars.2022.787992

Sunlight plays an important role for biological, chemical, and physical processes in the ocean. High-energetic ultraviolet (UV) radiation can have damaging and beneficial effects for aquatic organisms and its interaction with the ocean is generally complex. Most processes feedback with climate warming. Satellite-based observations of light penetration into the ocean in combination with modeling are used to understand these processes and make predictions for the future ocean and climate scenarios in general. Traditional satellite ocean color sensors don’t measure the ultraviolet range. Information on UV light penetration is only inferred indirectly from measurements in the visible wavelength range, naturally connected to lager uncertainties.

This study exploited backscattered UV to blue light data at continuous spectral resolution of 0.5 nm of the TROPOMI sensor onboard the Sentinel-5-Precursor satellite. We present the first direct satellite-based observations of shortwave penetration, in terms of the diffuse attenuation (Kd) into the ocean ranging from the ultraviolet to the blue spectral domain. Our approach is based on Differential Optical Absorption Spectroscopy to retrieve the vibrational Raman scattering (VRS) signal and then combined with coupled ocean-atmosphere radiative transfer modeling (RTM) to derive Kd in the UV range (312.5-338.5 nm and 356.5-390 nm), additionally to the blue Kd (390-423 nm). The VRS signal is well detected in TROPOMI measurements (fit errors <15%) and TROPOMI Kd retrievals exhibit low sensitivity to parametrization of oceanic and atmospheric effects and show good agreement to in situ Kd obtained from in situ measured underwater light spectra.

These products have high potential satisfying user needs in the modeling community which require spectral information on shortwave light penetration for improving estimates of the ocean’s heat budget, primary productivity, photochemical reaction rates of climatically important compounds, and the UV dose rates as an indicator for damaging effects on aquatic organisms.

Hunga Tonga-Hunga Ha'apai eruption

On 15th of January 2022, the undervolcano Hunga Tonga-Hunga Ha'apai (20.55°S, 175.40°W), ejected material consisting of gas, steam, and ash up to an altitude of 58 km. This plume height is exceptional and the highest known since satellite observations. Even the second largest volcanic eruption of Mount Pinatubo in the Philippines in 1991 „only“ reached a height of 35 km. Probably, the combination of volcanic heat and superheated moisture from the ocean pushes the aerosols in such unprecedented altitudes.

The uppermost part of the plume sublimated quickly due to the extreme dryness in the mesosphere. In around 30 km altitude, the volcanic plume formed an extensive umbrella carried westward by the strong stratospheric winds. As can be seen from the Figure, this umbrella rose and expanded due to thermal buoyancy and dispersion. It circled the globe within two weeks. The volcanic aerosols will remain in the stratosphere for a long time but have no significant impact on the global climate. The injected aerosol content of 0.4 teragram of sulphur dioxide was too low for that. For comparison: Mount Pinatubo emitted about 18.5 teragram of sulphur dioxide into the stratosphere, temporarily lowering the global temperature by about 0.6°C.

References:

Malinina, E., Rozanov, A., Niemeier, U., Wallis, S., Arosio, C., Wrana, F., Timmreck, C., von Savigny, C., and Burrows, J. P.: Changes in stratospheric aerosol extinction coefficient after the 2018 Ambae eruption as seen by OMPS-LP and MAECHAM5-HAM, Atmos. Chem. Phys., 21, 14871–14891, https://doi.org/10.5194/acp-21-14871-2021, 2021.

https://earthobservatory.nasa.gov

Expedition number 283 of the German research vessel SONNE, which was carried out in spring 2021, was rather special. Due to the Corona pandemic, many research cruises had been cancelled, and now several oceanographic moorings in the South Atlantic had to be recovered and new instruments deployed. Scientists and students from four institutes embarked on the long voyage, which startedin Emden for infection control reasons and ended there after 64 days at sea and more than 17,000 nautical miles. Our group from IUP deployed two tall moorings with current meters and thermistors as well as 5 bottom-mounted inverted echo sounders, which is part of the observational program of the Collaborative Research Center TRR 181 “Energy Transfers in Atmosphere and Ocean” (www.trr-energytransfers.de).

The objective of the experiment is to get many-months-long time series of current velocities and temperature to study the interaction of internal gravity waves emanating from the Walvis Ridge and Agulhas Eddies that travel from south of Africa into the South Atlantic. These interactions between waves and eddies and their exchange of kinetic energy are not yet fully understood. Tidal currents at seamounts and continental shelves, for example, exciteinternal gravity waves that can travel hundreds of kilometers across ocean basins before eventually contributing to turbulent mixing in the water column. Their loss of energy is determined by a number of processes and interactions. In our project, we study the scattering and refraction of tidal waves in the interior of the oceans with the goal of better integrating these processes intoclimate models.

The GMAP-2021 campaign
In October and November 2021, IUP Bremen participated in the GMAP-2021 (GEMS Map of Air Pollution) campaign in South Korea. This campaign brought together instruments from South Korea, the US, Belgium, the Netherlands, and Germany to collect data on air pollution in South Korea for the validation of the GEMS (Geostationary Environment Monitoring Spectrometer) satellite instrument. GEMS is the first geostationary satellite instrument dedicated to air quality, launched by the South Korean space agency in February 2020 and providing measurements of key pollutants over Asia in hourly resolution. Similar instruments will be launched by the US (TEMPO) and Europe (Sentinel-4) in the coming years.

During the GMAP campaign, IUP Bremen installed a multi-azimuth MAX-DOAS instrument on the rooftop of the NIER (National Institute of Environmental Research) building at Incheon. This instrument provides data on the abundance of NO2, HCHO, SO2and other pollutants valuable for long-term validation of GEMS retrievals. It will continue to operate at the location for the coming months. Similar instruments have been deployed by other groups in the Seoul Metropolitan Area and other parts of South Korea, and are expected to help in characterizing and improving the satellite data products.

In addition to the stationary measurements, a large number of mobile DOAS measurements was performed from cars to investigate the spatial variability of NO2, to monitor temporal changes and to estimate NOx emissions from Seoul. The observations show a large variability of NO2within individual GEMS satellite pixels, rapid changes over time and the impact of both, local emissions and transport to the observed NO2column amounts. These data are complemented by both in-situ and remote sensing observations from several aircraft overpasses over the same area.

Further reading:

Jhoon Kim et al., New Era of Air Quality Monitoring from Space: Geostationary Environment Monitoring Spectrometer (GEMS), BAMS, 2020, DOI: https://doi.org/10.1175/BAMS-D-18-0013.1

Scientists of the Institute of Environmental Physics are developing new optical sensors to image atmospheric Methane (CH4) and CO2 distributions from aircraft in a similar way as future satellites, but with higher sensitivity to point source emissions. The prototype of the push broom imaging spectrometer – called MAMAP2D-Light – was successfully mounted in the wing pods of the motor glider of Jade Hochschule Wilhelmshaven (see IUP picture of the month June 2021) and successfully performed its first flight over the power plant Jänschwalde near Cottbus, Germany.

Subsequent data analysis resulted in the image shown above, where the CO2 plume of the power plant Jänschwalde is clearly visible in reddish colors. The emissions estimated from this data set matches within its uncertainty range the average emissions during the week of the overflight, and the results and additional performance characteristics have been presented at the fall meeting of the American Geophysical Union in December 2021 (1). In summer 2022 this instrument will be flown onboard the German high altitude research aircraft HALO as part of the international COMET 2.0 campaign targeting high latitude emissions of CH4 and CO2 from wetlands as well as geological seeps and oil/gas production in Canada.

Contact: heinrich.bovensmann@uni-bremen.de

(1) Jakob Borchardt, Konstantin Gerilowski, Sven Krautwurst, Wilke Thomssen, Jan Franke, Martin Kumm, Pascal Janßen, Jens Wellhausen, Heinrich Bovensmann, John P. Burrows(2021), The New Imaging Spectrometer MAMAP2D-Light– Initial Calibration and First Measurement Results, [A25G-1759] presented at 2021 Fall Meeting, AGU, 13-17 Dec., https://agu2021fallmeeting-agu.ipostersessions.com/default.aspx?s=65-03-4F-E7-23-6B-ED-73-35-C6-6C-C5-C7-C1-9E-A9

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