Polarization-Based Image Segmentation and Height Estimation for Interferometric SAR

To find scatterers in a synthetic aperture radar (SAR) image, a modification is proposed to improve peak region segmentation (PRS) with region merging. The modification considers the polarization of each pixel before it is added to a segment to ensure the segment only contains pixels of the same polarization. Prior to region merging, the polarization of the segments is compared, so that only segments with the same polarization are merged into a single region. The segmented regions are used to find the height of each scatterer through interferometric SAR (IFSAR) processing. Multiple methods of IFSAR are examined to find the best height estimator. The best height results come from using all the pixels in the segment from all four polarization channels

Identifying and accounting for the Coriolis Effect in satellite NO2 observations and emission estimates

Recent developments in atmospheric remote sensing from satellites have made it possible to resolve daily emission plumes from industrial point sources, around the globe. Wind rotation aggregation coupled with statistical fitting is commonly used to extract emission estimates from these observations. These methods are used here to investigate how the Coriolis Effect influences the trajectory of observed emission plumes, and to assess the impact of this influence on satellite derived emission estimates. Of the 17 industrial sites investigated, nine showed the expected curvature for the hemisphere they reside in. Five showed no or negligible curvature, and two showed opposing or unusual curvature. The sites which showed conflicting curvature all reside in topographically diverse regions, where strong meso-gamma scale (2&ndash;20 km) turbulence dominates over larger synoptic circulation patterns. For high curvature cases the assumption that the wind-rotated plume aggregate is symmetrically distributed across the downwind axis breaks down, which impairs the quality of statistical fitting procedures. Using NOx emissions from Matimba power station as a test case, not compensating for Coriolis curvature resulted in an10 underestimation of &sim; 9 % on average for years 2018 to 2021. This study is the first formal observation of the Coriolis Effect and its influence on satellite observed emission plumes, and highlight both the variability of emission calculation methods and the need for a standardised scheme for this data to act as evidence for regulators.</p

Improving statistical skills through students’ participation in the development of resources

This paper summarizes the evaluation of a project that involved undergraduate mathematics students in the development of teaching and learning resources for statistics modules taught in various departments of a university. This evaluation regards students’ participation in the project and its impact on their learning of statistics, as characterized in terms of statistical reasoning, statistical thinking, and skills for statistical consultancy. The participation of students is evaluated from the viewpoint of communities of practice. The evaluation resulted in a characterization of the benefits of such a project and suggestions for implementations of future projects, and in addition brought to light new theoretical elements both as regards the learning of statistics and as regards communities of practice. In particular, the analysis highlighted contributions of the students involved to resource development practice in the community of university statistics teachers, as well as contributions to students’ learning as a result of participation in this community

Identifying and accounting for the Coriolis effect in satellite NO₂ observations and emission estimates

Recent developments in atmospheric remote sensing from satellites have made it possible to resolve daily emission plumes from industrial point sources around the globe. Wind rotation aggregation coupled with statistical fitting is commonly used to extract emission estimates from these observations. These methods are used here to investigate how the Coriolis effect influences the trajectory of observed emission plumes as well as to assess the impact of this influence on satellite-derived emission estimates. Of the 16 industrial sites investigated, 9 showed the expected curvature for the hemisphere that they reside in, 5 showed no or negligible curvature, and 2 showed opposing or unusual curvature. The sites that showed conflicting curvature reside in topographically diverse regions, where strong meso-γ-scale (2–20 km) turbulence dominates over larger synoptic circulation patterns. For high-curvature cases, the assumption that the wind-rotated plume aggregate is symmetrically distributed across the downwind axis breaks down, which impairs the quality of statistical fitting procedures. Using annual NOx emissions from Matimba power station as a test case, not compensating for Coriolis curvature resulted in an underestimation of ∼ 9 % on average for the years 2018 to 2021. This study is the first formal observation of the Coriolis effect and its influence on satellite-derived emission estimates, and it highlights both the variability in the emission calculation methods and the need for a standardised scheme for these data to act as evidence for regulators.</p

Ceilometer Aerosol Profiling versus Raman Lidar in the Frame of Interact Campaign of Actris

In this paper, multi-wavelength Raman lidar measurements are used to investigate the capability of ceilometers to provide reliable information about atmospheric aerosol properties through the INTERACT (INTERcomparison of Aerosol and Cloud Tracking) campaign carried out at the CNR-IMAA Atmospheric Observatory (760 m a.s.l., 40.60 N, 15.72 E), in the framework of ACTRIS (Aerosol Clouds Trace gases Research InfraStructure) FP7 project. This work is the first time that three different commercial ceilometers with an advanced Raman lidar are compared over a period of six month. The comparison of the attenuated backscatter coefficient profiles from a multi-wavelength Raman lidar and three ceilometers (CHM15k, CS135s, CT25K) reveals differences due to the expected discrepancy in the SNR but also due to effect of changes in the ambient temperature on the stability of ceilometer calibration over short and mid-term. Technological improvements of ceilometers towards their operational use in the monitoring of the atmospheric aerosol in the low and free troposphere are likely needed

Ceilometer aerosol profiling versus Raman lidar in the frame of the INTERACT campaign of ACTRIS

Despite their differences from more advanced and more powerful lidars, the low construction and operation cost of ceilometers (originally designed for cloud base height monitoring) has fostered their use for the quantitative study of aerosol properties. The large number of ceilometers available worldwide represents a strong motivation to investigate both the extent to which they can be used to fill in the geographical gaps between advanced lidar stations and also how their continuous data flow can be linked to existing networks of the more advanced lidars, like EARLINET (European Aerosol Research Lidar Network). In this paper, multi-wavelength Raman lidar measurements are used to investigate the capability of ceilometers to provide reliable information about atmospheric aerosol properties through the INTERACT (INTERcomparison of Aerosol and Cloud Tracking) campaign carried out at the CNR-IMAA Atmospheric Observatory (760 m a.s.l., 40.60◦ N, 15.72◦ E), in the framework of the ACTRIS (Aerosol Clouds Trace gases Research InfraStructure) FP7 project. This work is the first time that three different commercial ceilometers with an advanced Raman lidar are compared over a period of 6 months. The comparison of the attenuated backscatter coefficient profiles from a multiwavelength Raman lidar and three ceilometers (CHM15k, CS135s, CT25K) reveals differences due to the expected discrepancy in the signal to noise ratio (SNR) but also due to changes in the ambient temperature on the short and midterm stability of ceilometer calibration. Therefore, technological improvements are needed to move ceilometers towards operational use in the monitoring of atmospheric aerosols in the low and free tropospher

Linear Variable Filters for Satellite-Based Chemical Warfare Agent Detection

Previous research has indicated that it may be possible to detect chemical warfare agents in the thermal infrared with instruments such as the Infrared Atmospheric Sounding Interferometer (IASI) on the Meteorological Operational (MetOp) satellites. However, the low likelihood of the IASI overpass coinciding with an attack, coupled with the low spatial resolution of such an instrument would make it difficult to observe chemical attacks of a realistic scale. Additionally, these instruments have high size, weight and power needs and are thus less suited to smaller spacecraft. It was decided to investigate detection of Sarin and Sulphur Mustard using a linear variable filter – a filter for which the transmission properties vary along the filter’s length – as the spectral selection apparatus for a spaceborne infrared detector. Linear variable filters offer the advantage of being inexpensive and compact as well as offering multiple spectral bands, allowing for more affordable instruments to be constructed. These chemical agents were chosen for their use in recent conflicts as well as their high spectral absorption in the thermal infrared. First, to produce input spectral data, dispersion modelling was conducted using the "Urban Dispersion Model" producing atmospheric profiles for releases of Sarin and Sulphur Mustard. These profiles were then inputted to the "Oxford Reference Forward Model", along with other parameters such as temperature, emissivity, angle and altitude of satellite, and other atmospheric trace gases, with associated absorption cross-sections and line parameter data. This model calculated the radiative transfer, allowing the relevant bands of absorption to be selected. Commercially available linear variable filters were investigated, along with suitable detector technologies, and the necessary parameters for an appropriate filter and detector were determined from this investigation. Models for the filter and detector responses have been run for three different scenarios produced with the dispersion model. These include a scenario 1 minute after a 100kg release of Sarin, a scenario 1 minute after a 100 kg release of Sulphur Mustard, and a scenario in which neither gas is present, to allow for comparisons to be made and limits of detection to be established, including the necessary signal-to-noise ratio the instrument must achieve. Analysis of each of these scenarios utilised an idealised filter and detector constructed for the purposes of this work, and these were modelled using an optical model described in previous work by the authors. The results from the detector model suggest that the signal-to-noise ratio achieved by the instrument when observing these scenarios is more than sufficient for almost all wavelengths in the bands of interest. This indicates that it is likely that observations of Sarin and Sulphur Mustard releases could be successful under certain circumstances. Further analysis is required to establish a threshold for detectable concentration or the timeframe on which detections are viable, and there are still some technical barriers regarding the detectors to be overcome, but this work demonstrates the potential of using these filters for chemical warfare agent detection

Satellite Data Applications for Site-Specific Air Quality Regulation in the UK:Pilot Study and Prospects

Atmospheric composition data from satellite platforms offers great potential for improving current understanding of anthropogenic emissions. Whilst this data has been used extensively in research, its use by governments to regulate and assess site-specific legislation compliance is minimal. Here, we outline the regulatory context for air quality regulation in the UK, and present a pilot study highlighting the potential of current instruments. The pilot study demonstrates the capabilities and limitations of the TROPOspheric Monitoring Instrument (TROPOMI) for detecting and isolating emissions of NO2 from regulated UK point sources. This study successfully isolated NO2 emissions from a cluster of three closely situated regulated sites in the north east of England, despite their proximity to large urban sources. This is the first time these sites have been resolved from satellite-based observations, and serves as a clear demonstration of the potential of current and future Earth observation data products for site-specific monitoring and investigation within the UK

Ceilometer Aerosol Profiling versus Raman Lidar in the Frame of Interact Campaign of Actris

In this paper, multi-wavelength Raman lidar measurements are used to investigate the capability of ceilometers to provide reliable information about atmospheric aerosol properties through the INTERACT (INTERcomparison of Aerosol and Cloud Tracking) campaign carried out at the CNR-IMAA Atmospheric Observatory (760 m a.s.l., 40.60 N, 15.72 E), in the framework of ACTRIS (Aerosol Clouds Trace gases Research InfraStructure) FP7 project. This work is the first time that three different commercial ceilometers with an advanced Raman lidar are compared over a period of six month. The comparison of the attenuated backscatter coefficient profiles from a multi-wavelength Raman lidar and three ceilometers (CHM15k, CS135s, CT25K) reveals differences due to the expected discrepancy in the SNR but also due to effect of changes in the ambient temperature on the stability of ceilometer calibration over short and mid-term. Technological improvements of ceilometers towards their operational use in the monitoring of the atmospheric aerosol in the low and free troposphere are likely needed

The lesson learnt during interact - I and INTERACT - II actris measurement campaigns

The INTERACT-II (INTERcomparison of Aerosol and Cloud Tracking) campaign, performed at the CNR-IMAA Atmospheric Observatory (760 m a.s.l., 40.60° N, 15.72° E), aims to evaluate the performances of commercial automatic lidars and ceilometers for atmospheric aerosol profiling, through the comparison with Potenza EARLINET (European Aerosol Research Lidar NETwork) lidars. The results of the campaign and the overall lesson learnt within INTERACT-I and INTERACT-II ACTRIS campaigns will be presented