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Image of the Month

July 2022:

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

June 2022:

Figure 1:
Figure 1: (a) Diamond HK36TTC-ECO Super Dimona D-KWHV aircraft operated by Jade Hochschule Wilhelmshaven and the team from the University Bremen und Jade Hochschule. (b) University of Bremen measurement suite comprising an in-situ greenhouse gas analyser from LRG and a 5-hole turbulence probe. Both are mounted underneath the right wing in an underwing pod. (c) Fligh-by at the ICOS measurement tower in Steinkimmen/Ganderkesee operated be the DWD during the second calibration flight. (d) Vertical wind profile measured during the very first calibration flight of the turbulence probe.

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

May 2022:

Example Figure:
Example Figure: TROPOMI (A) Kd-UVAB, (B) Kd-UVA, and (C) Kd-blue in the Atlantic Ocean gridded at 0.083 as mean for 11 May to 9 June 2018. Accordingly, Kd-UVAB, Kd-UVA, and Kd-blue measured in-situ at 19 stations during expedition PS113 are overlayed as diamonds (match-ups) and circles (unmatched stations). Adapted from Oelker et al. 2022, Fig. 5.

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.

April 2022:

Figure:
Figure: Colour ratio gradients (a,b) as altitudinal changes of the radiance ratio L(869nm)/L(460nm), as well as retrieved extinction coefficients at 869 nm (c,d) from OMPS-LP limb observations of two selected orbits. Areas of NaN values are scratched out. The map in the top row shows the location of the orbits and the volcano (triangle).

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

March 2022:

Figure:
Figure: Deployment of an acoustic Doppler current profiler (ADCP) during expedition SO283 with the research vessel SONNE in the South Atlantic, April 2021 (top). Internal wave energy flux (red) and the pathway of Agulhas Eddies (blue) in the South Atlantic. Stars and circles denote deployment positions of instruments (bottom left). Current measurements (arrows) along the ship track and sea surface height (SSH) from satellite altimetry (bottom right).

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.

February 2022:

Figure:
Figure: GMAP-2021 campaign in South Korea. Top left: Group picture of some participants. Top right: The IUP Bremen MAX-DOAS instrument on the roof of the NIER building. Bottom figures: Two days of NO2 observations in the Seoul Metropolitan Area. Background values are GEMS tropospheric NO2 columns retrieved by IUP Bremen. The overlaid line are matching car-DOAS measurements performed within +/- 2 hours of the satellite overpass.

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

January 2022:

Figure 1:
Figure 1: The Carbon Dioxide (CO2) plume emitted from the power plant Jänschwalde observed with the new airborne instrument MAMAP2D-Light could be detected up to 10 km away from the power plant itself. Reddish colors indicate high CO2 concentrations, while the white areas have been filtered out due to too low signal over water (Image: IUP, University Bremen).

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