European Facility For Airborne Research April 26, 2024, 08:34
AROMAPEX
APEX flights for the AROMAT-2 activity
Scientific project
TA-007. Airborne imaging for environmental science applications
None
CALCAN (BOSCORNEA) Andreea
educational background: -PhD in Atmospheric Physics - Cloud microphysics research, -master of science in photonics, lasers, plasma and spectroscopy and I follow courses in Earth and Atmospheric Physics.
DO228-212 - DLR
The AROMAT campaign was held in Romania in September 2014 [1] to test newly developed airborne instruments dedicated to air quality in the context of satellite validation. In particular, two airborne imaging DOAS systems were operated, namely the AirMAP from Uni. Bremen [2] and SWING from BIRA, respectively from the FUB Cessna and from a flying wing UAV (Uni. Galati-Reev River Aerospace). These instruments revealed the NO2 horizontal distributions in the exhaust plume of large power plants near Craiova. The AirMAP/Cessna could also be operated above Bucharest and map the whole city. These two geophysical targets (Bucharest and the power plant) are visible in satellite data (OMI) but present different characteristics: the former is a large extended source with moderate NO2 columns (about 1x1016 molec/cm2), the latter produces very dense and localized plume (about 1x1017 molec/cm2). All airborne instruments were operated successfully during AROMAT, nevertheless, several lessons were learned that called for a follow-up and improved experiment. In particular, it appears scientifically interesting to add a second airborne imager from a manned aircraft. This would increase the possibility of measuring satellite overpasses, which were limited in the two weeks of AROMAT-1 due to weather conditions and technical issues. The objective of this proposal is to include the APEX instrument [3] in this AROMAT-2 campaign, which is supported by ESA. APEX is mounted onboard the DLR Do228 aircraft. It will be set in unbinned spectral mode, to map the tropospheric NO2 columns above the same targets as AROMAT-1. The possibility to measure NO2 from APEX has already been demonstrated over Zurich [4]. Moreover, BIRA and VITO, part of the AROMAPEX consortium, are involved in a national project to perform similar APEX measurements over the large Belgian cities. The objectives of the AROMAPEX experiment consists in :(1) Operating APEX and AirMAP in formation above the same area in a reasonably short time interval. This is the first opportunity to intercompare two different airborne trace gases imagers and to evaluate their respective performance and limitations. Note that the SWING-UAV measurements will also be compared with APEX and AirMAP, but they suffer from two practical limitations compared to measurements from a traditional aircraft: the area that can be covered is smaller with the UAV and this platform will not be allowed to fly above Bucharest.(2) Flying the two aircraft in different locations and times to increase the area covered and adapt the flight schedule to the overpasses time of two air quality space borne instruments (OMI, GOME2) in the same day. This will enable us, beside the comparison of APEX and AirMAP with satellite data, to study the diurnal variation of NO2. (3) Operating the two aircraft above the power plant, but with the AirMAP set in its UV mode, which is optimal for the detection of SO2. We have already detected elevated levels of SO2 in the plant plume during AROMAT-1. These combined measurements will reveal accurately the SO2 and NO2 columns in the same plume. The collected airborne dataset will be compared with coincident UAV based observations and ground-based measurements, including car-based DOAS data, a Pandora system, and NO2/SO2 cameras. Results will be exploited in particular in the Phd work of the students of the team.[1] http://uv-vis.aeronomie.be/aromat/[2] Schönhardt, A, A wide field-of-view imaging DOAS instrument for continuous trace gas mapping from aircraft, Atmos. Meas. Tech. Discuss., 7, 3591-3644, doi:10.5194/amtd-7-3591-2014, 2014[3] Itten et al. APEX – the Hyperspectral ESA Airborne Prism Experiment, Sensors, 8, 6235–6259, doi:10.3390/s8106235, 2008.[4] Popp et al. High-resolution NO2 remote sensing from the Airborne Prism EXperiment (APEX) imaging spectrometer, Atmos. Meas. Tech., 5, 2211–2225, doi:10.5194/amt-5-2211-2012, 2012.
Clear sky offers the best measurement conditions, broken clouds are acceptable.
The measurements will be made during day time. We will optimize the flight schedule every day with the Romanian authorities, taking into account the satellite overpasses and the weather prognosis.
The campaign will be held in Romania and this research is only feasible in the framework of a larger field campaign that provides additional data (see above). The aircraft will be based in Baneasa airport, in the Bucharest urban area. The consortium has already experience and good connections at this airport, in particular at the School academy, which supported the team during AROMAT-1 for the logistics and the administrative issues. The two geophysical targets are Bucharest (44°25′57″N, 26°06′14″E) and the Turceni power plant (44°40'7.74"N, 23°24'24.00"E) in the Jiu Valley. These locations have been chosen since they are the main visible NO2 spots on satellite data in Romania, and comparison with satellite data is a key objective of the campaign.
15 flight hours are needed to reach the scientific objectives (10 flight hours for the transit to Bucharest and 5 for data acquisition; Bucharest (2h) and Turceni (3h)).The final flight patterns have to be approved by the national authorities and the operator, but, considering that the APEX imaging spectrometer operation needs a horizontal scanning flight pattern, we will apply the already used and tested flight strategy presented by Popp at al., 2012.
Georeferenced spectra from APEX is compulsory to reach the scientific objectives of the proposal.
APEX
not the case, no additional instruments are required
However, if possible one or two aircraft operators from the INCAS ATMOSLAB team may attend some of the flights in order to improve their knowledge and experience. The ATMOSLAB team is established since 2011 and the operators need more experience in flight operation so that an exchange of knowledge between the two teams would be welcome.
2
We will have the other airborne experiments that were already operated in AROMAT-1 (AirMAP onboard the FUB Cessna), two UAVs, and KNMI tropospheric balloons. We will also operate several ground based instruments (lidar, car-based DOAS, …).
All acquired data will be handled by the APEX processing and archiving facility (PAF), hosted by VITO in the APEX Operations Center (AOC) at Mol, Belgium. The APEX PAF is defined as the combination of all hardware and software components and their interfaces required for handling and processing APEX imagery and its related data to level 0 and level 1 data. The processed data will be made available to the scientific partners based on an FTP server.
Building on the experience of both the Popp et al. (2012) pilot study, of which BIRA was co-author, and the Belspo (Belgium Science Policy) funded STEREO III BUMBA (Belgian urban NO2 monitoring based on APEX hyperspectral data) project, which started in December 2014, retrieval algorithms based on existing tools developed for satellite retrieval are adapted to retrieve NO2 columns from the high resolution APEX observations. The BUMBA project focuses on the processing of the APEX data in its unbinned mode in order to optimize both signal-noise-ratio and spectral resolution performances, allowing for better discrimination of the fine scale structures in the NO2 field. After spatial aggregation of the imaging spectrometer data to increase the signal-noise-ratio, a spatial resolution of approximately 50 meter is expected to be reached.
The differential optical absorption spectroscopy technique (DOAS) will be applied to the observed backscattered solar radiation in the visible wavelength region, in order to quantify the abundance of NO2 in the atmosphere, based on its molecular absorption structures. This will be done by an adapted version of the QDOAS spectral non-linear least-squares fitting tool, developed at BIRA-IASB (Danckaert et al., 2014). The resulting fit coefficients are NO2 differential slant column densities (DSCDs), being the concentration of NO2 integrated along the effective light path with respect to a reference spectrum containing low NO2 absorption. A retrieved SCD(Slant Column Densities) depends on multiple light paths of backscattered solar radiation, contributing to the observed spectrum. Transfer of radiation in the atmosphere needs to be modeled and appropriate enhancement factors need to be calculated in order to derive the effective optical path length through the atmosphere and thus to be able to interpret the observations. In order to convert slant to vertical column densities, air mass factors (AMFs) need to be calculated with the radiative transfer model (RTM) UVspec/DISORT (Mayer and Killing, 2005). The RTM simulates the radiative transfer in the atmosphere based on a priori information on the atmosphere’s state. The coincident ground-based observations will be used as ancillary data in the retrieval scheme or for comparisons with the airborne data. In particular, several MAX-DOAS systems will be operated during the campaign (Pandora in Bucharest, car-based DOAS in Bucharest and around the power plant). These instruments are also quantifying the columns of NO2 and SO2 and are thus directly comparable with APEX. During the campaign, an aerosol particle sizer will also be operated from the INCAS ATMOSLAB UAV, this will help to quantify the aerosol loading, important for the radiative transfer step of the DOAS data analysis.
ReferencesDanckaert, T., Fayt, C., and Van Roozendael, M.: QDOAS software user manual 2.108, IASB/BIRA, Uccle, Belgium, 2014, available at http://uv-vis.aeronomie.be/software/QDOAS/QDOAS_manual.pdf, last access: 04 November 2014.
D’Odorico, P. and Schaepman, M.: Monitoring the spectral performance of the APEX imaging spectrometer for inter-calibration of satellite missions, Remote Sensing Laboratories, Department of Geography, University of Zurich, 2012.
Itten, K. I., Dell’Endice, F., Hueni, A., Kneubühler, M., Schläpfer, D., Odermatt, D., Seidel, F., Huber, S., Schopfer, J., Kellenberger, T., Bühler, Y., D’Odorico, P., Nieke, J., Alberti, E., and Meuleman, K.: APEX – the Hyperspectral ESA Airborne Prism Experiment, Sensors, 8, 6235–6259, doi:10.3390/s8106235, 2008.
Jehle, M., Hueni, A., Damm, A., D’Odorico, P., Kneubühler, M., Schläpfer, D., and Schaepman, M. E.: APEX – current status, performance and product generation, in: Proc. IEEE Sensors 2010 Conference, Waikoloa, Hawaii, USA, 1 - 4 November, 2010, doi:10.1109/ICSENS.2010.5690122, 2010.
Mayer, B. and Kylling, A.: Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use, Atmos. Chem. Phys., 5, 1855–1877, doi:10.5194/acp-5-1855-2005, 2005.
Popp, C., Brunner, D., Damm, A., Van Roozendael, M., Fayt, C., and Buchmann, B.: High-resolution NO2 remote sensing from the Airborne Prism EXperiment (APEX) imaging spectrometer, Atmos. Meas. Tech., 5, 2211–2225, doi:10.5194/amt-5-2211-2012, 2012.
The principal flight period will be defined between 15.08.2015 and 31.08.2015. But the measurement flight tests can be performed in September 2015 (depending of solar zenith angles and weather conditions).
Yes
The training benefit of the project is important due to the direct implications of two PhD students in the project. MsC students from INCAS/University of Bucharest will also be involved on site. The atmospheric physics group at INCAS is a recently established group. Its members are motivated to learn and collaborate with experienced researcher in atmospheric science from other countries. The dataset obtained from the measurements will be used for the research studies of young scientists and the diploma work of students. The project will lead to scientific articles, in particular for the students.
As described above, the AROMAPEX project will be clustered with an ESA funded campaign, AROMAT-2, which includes the Uni. Bremen AirMAP. The added value of APEX is the opportunity it gives to intercompare these two imaging systems above well characterized areas. It will also enable us to optimize the measurements during satellite overpass by covering larger areas during a longer timespan.
5