scholarly journals Remote sensing of methane plumes: instrument tradeoff analysis for detecting and quantifying local sources at global scale

2021 ◽  
Vol 14 (12) ◽  
pp. 7999-8017
Author(s):  
Siraput Jongaramrungruang ◽  
Georgios Matheou ◽  
Andrew K. Thorpe ◽  
Zhao-Cheng Zeng ◽  
Christian Frankenberg
Keyword(s):  
Remote Sensing ◽  
Spectral Resolution ◽  
Surface Albedo ◽  
Complex Surface ◽  
Low Noise ◽  
Optical Absorption Spectroscopy ◽  
Modeling Framework ◽  
Precision Error ◽  
Polynomial Degree ◽  
The Impact

Abstract. Methane (CH4) is the second most important anthropogenic greenhouse gas with a significant impact on radiative forcing, tropospheric air quality, and stratospheric water vapor. Remote sensing observations enable the detection and quantification of local methane emissions across large geographical areas, which is a critical step for understanding local flux distributions and subsequently prioritizing mitigation strategies. Obtaining methane column concentration measurements with low noise and minimal surface interference has direct consequences for accurately determining the location and emission rates of methane sources. The quality of retrieved column enhancements depends on the choices of the instrument and retrieval parameters. Here, we studied the changes in precision error and bias as a result of different spectral resolutions, instrument optical performance, and detector exposure times by using a realistic instrument noise model. In addition, we formally analyzed the impact of spectrally complex surface albedo features on retrievals using the iterative maximum a posteriori differential optical absorption spectroscopy (IMAP-DOAS) algorithm. We built an end-to-end modeling framework that can simulate observed radiances from reflected solar irradiance through a simulated CH4 plume over several natural and artificial surfaces. Our analysis shows that complex surface features can alias into retrieved methane abundances, explaining the existence of retrieval biases in current airborne methane observations. The impact can be mitigated with higher spectral resolution and a larger polynomial degree to approximate surface albedo variations. Using a spectral resolution of 1.5 nm, an exposure time of 20 ms, and a polynomial degree of 25, a retrieval precision error below 0.007 mole m−2 or 1.0 % of total atmospheric CH4 column can be achieved for high albedo cases, while minimizing the bias due to surface interference such that the noise is uncorrelated among various surfaces. At coarser spectral resolutions, it becomes increasingly harder to separate complex surface albedo features from atmospheric absorption features. Our modeling framework provides the basis for assessing tradeoffs for future remote sensing instruments and algorithmic designs. For instance, we find that improving the spectral resolution beyond 0.2 nm would actually decrease the retrieval precision, as detector readout noise will play an increasing role. Our work contributes towards building an enhanced monitoring system that can measure CH4 concentration fields to determine methane sources accurately and efficiently at scale.

scholarly journals Remote sensing of methane plumes: instrument tradeoff analysis for detecting and quantifying local sources at global scale

2021 ◽  
Author(s):  
Siraput Jongaramrungruang ◽  
Georgios Matheou ◽  
Andrew K. Thorpe ◽  
Zhao-Cheng Zeng ◽  
Christian Frankenberg
Keyword(s):  
Remote Sensing ◽  
Spectral Resolution ◽  
Surface Albedo ◽  
Complex Surface ◽  
Low Noise ◽  
Optical Absorption Spectroscopy ◽  
Precision Error ◽  
Polynomial Degree ◽  
Modelling Framework ◽  
The Impact

Abstract. Methane (CH4) is the 2nd most important anthropogenic greenhouse gas with a significant impact on radiative forcing, tropospheric air quality and stratospheric water vapor. Remote-sensing observations enable the detection and quantification of local methane emissions across large geographical areas, which is a critical step for understanding local flux distributions and subsequently prioritizing mitigation strategies. Obtaining methane column concentration measurements with low noise and minimal surface interference has direct consequences for accurately determining the location and emission rates of methane sources. The quality of retrieved column enhancements depends on the choices of instrument and retrieval parameters. Here, we studied the changes in precision error and bias as a result of different spectral resolutions, instrument optical performance and detector exposure times by using a realistic instrument noise model. In addition, we formally analysed the impact of spectrally complex surface albedo features on retrievals using the Iterative Maximum a Posteriori- Differential Optical Absorption Spectroscopy (IMAP-DOAS) algorithm. We built an end-to-end modelling framework that can simulate observed radiances from reflected solar irradiance through a simulated CH4 plume over several natural and man-made surfaces. Our analysis shows that complex surface features can alias into retrieved methane abundances, explaining the existence of retrieval biases in current airborne methane observations. The impact can be mitigated with higher spectral resolution and a larger polynomial degree to approximate surface albedo variations. Using a spectral resolution of 1.5 nm, an exposure time of 20 ms, and a polynomial degree of 25, a retrieval precision error below 0.007 mole m−2 or 1.0 % of total atmospheric CH4 column can be achieved for high albedo cases, while minimizing the bias due to surface interference such that the noise is uncorrelated among various surfaces. At coarser spectral resolutions, it becomes increasingly harder to separate complex surface albedo features from atmospheric absorption features. Our modelling framework provides the basis for assessing trade-offs for future remote-sensing instruments and algorithmic designs. For instance, we find that improving the spectral resolution beyond 0.2 nm would actually decrease the retrieval precision as detector readout noise will play an increasing role. Our work contributes towards building an enhanced monitoring system that can measure CH4 concentration fields to determine methane sources accurately and efficiently at scale.

scholarly journals Quantifying the impact of aerosol scattering on the retrieval of methane from airborne remote sensing measurements

2020 ◽  
Vol 13 (12) ◽  
pp. 6755-6769
Author(s):  
Yunxia Huang ◽  
Vijay Natraj ◽  
Zhao-Cheng Zeng ◽  
Pushkar Kopparla ◽  
Yuk L. Yung
Keyword(s):  
Remote Sensing ◽  
Surface Albedo ◽  
Single Scattering ◽  
Water Soluble ◽  
Transfer Model ◽  
Background Values ◽  
Ch4 Emissions ◽  
Aerosol Scattering ◽  
The Impact ◽  
Retrieval Bias

Abstract. As a greenhouse gas with strong global warming potential, atmospheric methane (CH4) emissions have attracted a great deal of attention. Although remote sensing measurements can provide information about CH4 sources and emissions, accurate retrieval is challenging due to the influence of atmospheric aerosol scattering. In this study, imaging spectroscopic measurements from the Airborne Visible/Infrared Imaging Spectrometer – Next Generation (AVIRIS-NG) in the shortwave infrared are used to compare two retrieval techniques – the traditional matched filter (MF) method and the optimal estimation (OE) method, which is a popular approach for trace gas retrievals. Using a numerically efficient radiative transfer model with an exact single-scattering component and a two-stream multiple-scattering component, we also simulate AVIRIS-NG measurements for different scenarios and quantify the impact of aerosol scattering in the two retrieval schemes by including aerosols in the simulations but not in the retrievals. The presence of aerosols causes an underestimation of CH4 in both the MF and OE retrievals; the biases increase with increasing surface albedo and aerosol optical depth (AOD). Aerosol types with high single-scattering albedo and low asymmetry parameter (such as water-soluble aerosols) induce large biases in the retrieval. When scattering effects are neglected, the MF method exhibits lower fractional retrieval bias compared to the OE method at high CH4 concentrations (2–5 times typical background values) and is suitable for detecting strong CH4 emissions. For an AOD value of 0.3, the fractional biases of the MF retrievals are between 1.3 % and 4.5 %, while the corresponding values for OE retrievals are in the 2.8 %–5.6 % range. On the other hand, the OE method is an optimal technique for diffuse sources (<1.5 times typical background values), showing up to 5 times smaller fractional retrieval bias (8.6 %) than the MF method (42.6 %) for the same AOD scenario. However, when aerosol scattering is significant, the OE method is superior since it provides a means to reduce biases by simultaneously retrieving AOD, surface albedo, and CH4. The results indicate that, while the MF method is good for plume detection, the OE method should be employed to quantify CH4 concentrations, especially in the presence of aerosol scattering.

Towards DOAS measurements with a picometre spectral resolution

2021 ◽  
Author(s):  
Jonas Kuhn ◽  
Nicole Bobrowski ◽  
Thomas Wagner ◽  
Ulrich Platt
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Spectral Resolution ◽  
Trace Gases ◽  
High Resolution Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Oh Radicals ◽  
Near Ir ◽  
Atmospheric Remote Sensing ◽  
Moderate Resolution

&lt;p&gt;Differential Optical Absorption Spectroscopy (DOAS) has proven to be very useful to study the composition and dynamics of Earth&amp;#8217;s atmosphere. Compact grating spectrographs (GSs) with moderate spectral resolution (ca. 1nm) allow to quantify the absorption of many trace gases along atmospheric light paths from ground to space borne platforms.&lt;/p&gt;&lt;p&gt;Since the width of a rovibronic absorption line of a small molecule in the UV to near IR spectral range is in the picometre range, increasing the spectral resolution of DOAS measurements largely increases their selectivity and in many cases also their sensitivity. In addition, further trace gases (e.g. OH radicals) or isotopes of trace gases could be detected, while common problems due to Fraunhofer line undersampling were reduced. However, since high resolution GSs are bulky (immobile) instruments with a strongly reduced light throughput, hardly any high resolution DOAS measurements have been performed.&lt;/p&gt;&lt;p&gt;Since more than a century, Fabry P&amp;#233;rot Interferometers (FPIs) have been successfully used for high resolution spectroscopy in many scientific fields, where their light throughput advantage over grating spectrographs for higher resolving powers is well known. However, except for a few studies, FPIs&lt;br&gt;received hardly any attention in atmospheric trace gas remote sensing. We examine the light throughput of GSs and FPI spectrographs regarding spectral resolution and spectrograph size (i.e. mobility). We find that robust and mobile high resolution FPI spectrograph implementations can be by orders of magnitude smaller than GSs with the same spectral resolution. A compact high resolution FPI spectrograph prototype was already successfully tested in the field. Further, the light throughput can be optimised to allow for passive scattered sunlight measurements with similar SNR as moderate resolution DOAS measurements while, at the same time, attaining spectral resolutions in the picometre range.&lt;/p&gt;&lt;p&gt;High resolution FPI spectrographs might allow for a multitude of applications in atmospheric remote sensing. A few examples include scattered sunlight absorption measurements of many atmospheric trace gases and their isotopes, the quantification of tropospheric and volcanic OH radicals, high resolution O2 measurements for radiative transfer investigation and aerosol studies, and solar induced chlorophyll fluorescence quantification using Fraunhofer lines.&lt;/p&gt;

scholarly journals SPACE MONITORING OF ANTHROPOGENIC IMPACTS ON SOILS AND THE WATER ENVIRONMENT ASSOCIATED WITH SOLID DOMESTIC WASTE: SCIENTIFIC AND EDUCATIONAL ASPECTS (SPACE ENVIRONMENTAL WATCH)

2017 ◽  
pp. 5-12
Author(s):  
Mihail Shakhramanyan ◽  
Maretta Kazaryan ◽  
Andrey Richter
Keyword(s):  
Remote Sensing ◽  
Solid Waste ◽  
Chemical Reactions ◽  
Spectral Resolution ◽  
Domestic Waste ◽  
Solid Domestic Waste ◽  
Research Activities ◽  
The Earth ◽  
Physical Chemical ◽  
The Impact

A new technology of monitoring and control of solid waste, based on the reception and processing of the Earth remote sensing data with different spatial resolution and spectral resolution is proposed. The technology is based on the processing of multispectral and hyperspectral images from space in special software products, the identification and analysis of solid waste from small (suburban, road clutter) to large (industrial and urban landfills), depending on the spatial and spectral resolution of the space image. At present, software complexes for processing (deciphering) of space images of solid domestic waste and their adjacent territories have been developed. With the help of these software complexes, it became possible to identify unauthorized landfills, to determine the correctness of operation of existing landfills in accordance with existing regulatory documents, to determine the sequence of liquidation of various landfills, depending on the degree of their negative impact on the environment and human health. The introduction of the proposed technology can provide substantial assistance to various ministries, departments and the public in detecting at an early stage the places of clutter, the so-called pre-landfills, which, if not to take preventive measures, can become real garbage dumps with all the ensuing environmental problems. It is important that schools and universities, for which this work will be attractive both in terms of planning and implementation of research activities, education of young people with an active life position in terms of ecology and environmental protection, be included in the implementation of the "Space Ecological Watch" project. It should be borne in mind that SHW landfills are basically "the reactors" in which various physical-chemical reactions (combustion, oxidation, etc.) are rapidly occurring; besides SWLs are of considerable interest for educational and research processes both in secondary and higher schools. Moreover, many parameters of these physical-chemical reactions in the time-mode, close to the real one, can be controlled by methods of remote sensing of the Earth from space. We propose to organize the International Competition "Space Environmental Watch" with the participation of students and schoolchildren from different countries of the world. This Competition will be based on the technology described above, will have the following nominations: - identification of unauthorized landfills; - landfills Information validity check; - assessment of the impact of solid waste landfills on the environment. According to the results of the competition, a digital map with identified unauthorized garbage dumps and an assessment of their impact on the environment can be made on the Internet.

scholarly journals An improved air mass factor calculation for nitrogen dioxide measurements from the Global Ozone Monitoring Experiment-2 (GOME-2)

2020 ◽  
Vol 13 (2) ◽  
pp. 755-787 ◽  
Author(s):  
Song Liu ◽  
Pieter Valks ◽  
Gaia Pinardi ◽  
Jian Xu ◽  
Athina Argyrouli ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Surface Albedo ◽  
Optical Absorption Spectroscopy ◽  
Model Parameters ◽  
Air Mass ◽  
Cloud Parameters ◽  
Tropospheric No2 ◽  
Mass Factor ◽  
Ozone Monitoring ◽  
The Impact

Abstract. An improved tropospheric nitrogen dioxide (NO2) retrieval algorithm from the Global Ozone Monitoring Experiment-2 (GOME-2) instrument based on air mass factor (AMF) calculations performed with more realistic model parameters is presented. The viewing angle dependency of surface albedo is taken into account by improving the GOME-2 Lambertian-equivalent reflectivity (LER) climatology with a directionally dependent LER (DLER) dataset over land and an ocean surface albedo parameterisation over water. A priori NO2 profiles with higher spatial and temporal resolutions are obtained from the IFS (CB05BASCOE) chemistry transport model based on recent emission inventories. A more realistic cloud treatment is provided by a clouds-as-layers (CAL) approach, which treats the clouds as uniform layers of water droplets, instead of the current clouds-as-reflecting-boundaries (CRB) model, which assumes that the clouds are Lambertian reflectors. On average, improvements in the AMF calculation affect the tropospheric NO2 columns by ±15 % in winter and ±5 % in summer over largely polluted regions. In addition, the impact of aerosols on our tropospheric NO2 retrieval is investigated by comparing the concurrent retrievals based on ground-based aerosol measurements (explicit aerosol correction) and the aerosol-induced cloud parameters (implicit aerosol correction). Compared with the implicit aerosol correction utilising the CRB cloud parameters, the use of the CAL approach reduces the AMF errors by more than 10 %. Finally, to evaluate the improved GOME-2 tropospheric NO2 columns, a validation is performed using ground-based multi-axis differential optical absorption spectroscopy (MAXDOAS) measurements at different BIRA-IASB stations. At the suburban Xianghe station, the improved tropospheric NO2 dataset shows better agreement with coincident ground-based measurements with a correlation coefficient of 0.94.

scholarly journals Capability of Remote Sensing Images to Distinguish the Urban Surface Materials: A Case Study of Venice City

2021 ◽  
Vol 13 (19) ◽  
pp. 3959
Author(s):  
Rosa Maria Cavalli
Keyword(s):  
Remote Sensing ◽  
Spatial Resolution ◽  
Spectral Range ◽  
Spectral Resolution ◽  
Urban Areas ◽  
Spectral Characteristics ◽  
Urban Surface ◽  
Remote Sensing Images ◽  
Surface Materials ◽  
The Impact

Many countries share an effort to understand the impact of growing urban areas on the environment. Spatial, spectral, and temporal resolutions of remote sensing images offer unique access to this information. Nevertheless, their use is limited because urban surface materials exhibit a great diversity of types and are not well spatially and spectrally distinguishable. This work aims to quantify the effect of these spatial and spectral characteristics of urban surface materials on their retrieval from images. To avoid other sources of error, synthetic images of the historical center of Venice were analyzed. A hyperspectral library, which characterizes the main materials of Venice city and knowledge of the city, allowed to create a starting image at a spatial resolution of 30 cm and spectral resolution of 3 nm and with a spectral range of 365–2500 nm, which was spatially and spectrally resampled to match the characteristics of most remote sensing sensors. Linear spectral mixture analysis was applied to every resampled image to evaluate and compare their capabilities to distinguish urban surface materials. In short, the capability depends mainly on spatial resolution, secondarily on spectral range and mixed pixel percentage, and lastly on spectral resolution; impervious surfaces are more distinguishable than pervious surfaces. This analysis of capability behavior is very important to select more suitable remote sensing images and/or to decide the complementarity use of different data.

scholarly journals An improved air mass factor calculation for NO<sub>2</sub> measurements from GOME-2

2019 ◽  
Author(s):  
Song Liu ◽  
Pieter Valks ◽  
Gaia Pinardi ◽  
Jian Xu ◽  
Athina Argyrouli ◽  
...  
Keyword(s):  
Surface Albedo ◽  
Transport Model ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Model Parameters ◽  
Air Mass ◽  
Cloud Parameters ◽  
Tropospheric No2 ◽  
Mass Factor ◽  
The Impact

Abstract. An improved tropospheric nitrogen dioxide (NO2) retrieval algorithm from the Global Ozone Monitoring Experiment-2 (GOME-2) instrument based on air mass factor (AMF) calculations performed with more realistic model parameters is presented. The viewing angle-dependency of surface albedo is taken into account by improving the GOME-2 Lambertian-equivalent reflectivity (LER) climatology with a directionally dependent LER (DLER) dataset over land and an ocean surface albedo parametrization over water. A priori NO2 profiles with higher spatial and temporal resolutions are obtained from the IFS(CB05BASCOE) chemistry transport model based on recent emission inventories. A more realistic cloud treatment is provided by a Cloud-As-Layers (CAL) approach, which treats the clouds as uniform layers of water droplets, instead of the current Clouds-as-Reflecting-Boundaries (CRB) model, which assumes the clouds as Lambertian reflectors. Improvements in the AMF calculation affect the tropospheric NO2 columns on average within ±15 % in winter and ±5 % in summer over largely polluted regions. In addition, the impact of aerosols on our tropospheric NO2 retrieval is investigated by comparing the concurrent retrievals based on ground-based aerosol measurements (explicit aerosol correction) and aerosol-induced cloud parameters (implicit aerosol correction). Compared to the implicit aerosol correction through the CRB cloud parameters, the use of CAL reduces the AMF errors by more than 10 %. Finally, to evaluate the improved GOME-2 tropospheric NO2 columns, a validation is performed using ground-based Multi-AXis Differential Optical Absorption Spectroscopy (MAXDOAS) measurements at the BIRA-IASB Xianghe station. The improved tropospheric NO2 dataset shows good agreement with coincident ground-based measurements with a correlation coefficient of 0.94 and a relative difference of −9.9 % on average.

Impact of LULC Changes on LST in Rajshahi District of Bangladesh: A Remote Sensing Approach

2020 ◽  
Vol 3 (1) ◽  
pp. 11-23 ◽  
Author(s):  
Abdulla Al Kafy ◽  
Abdullah Al-Faisal ◽  
Mohammad Mahmudul Hasan ◽  
Md. Soumik Sikdar ◽  
Mohammad Hasib Hasan Khan ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Surface Temperature ◽  
Land Surface ◽  
Agricultural Land ◽  
Global Climate ◽  
Urban Expansion ◽  
Water Bodies ◽  
Landsat 8 ◽  
Lulc Changes ◽  
The Impact

Urbanization has been contributing more in global climate warming, with more than 50% of the population living in cities. Rapid population growth and change in land use / land cover (LULC) are closely linked. The transformation of LULC due to rapid urban expansion significantly affects the functions of biodiversity and ecosystems, as well as local and regional climates. Improper planning and uncontrolled management of LULC changes profoundly contribute to the rise of urban land surface temperature (LST). This study evaluates the impact of LULC changes on LST for 1997, 2007 and 2017 in the Rajshahi district (Bangladesh) using multi-temporal and multi-spectral Landsat 8 OLI and Landsat 5 TM satellite data sets. The analysis of LULC changes exposed a remarkable increase in the built-up areas and a significant decrease in the vegetation and agricultural land. The built-up area was increased almost double in last 20 years in the study area. The distribution of changes in LST shows that built-up areas recorded the highest temperature followed by bare land, vegetation and agricultural land and water bodies. The LULC-LST profiles also revealed the highest temperature in built-up areas and the lowest temperature in water bodies. In the last 20 years, LST was increased about 13ºC. The study demonstrates decrease in vegetation cover and increase in non-evaporating surfaces with significantly increases the surface temperature in the study area. Remote-sensing techniques were found one of the suitable techniques for rapid analysis of urban expansions and to identify the impact of urbanization on LST.

ИССЛЕДОВАНИЕ НИТРИД-ГАЛЛИЕВЫХ МАЛОШУМЯЩИХ УСИЛИТЕЛЕЙ ПРИ КРИОГЕННЫХ ТЕМПЕРАТУРАХ

2020 ◽  
Vol 96 (3s) ◽  
pp. 347-352
Author(s):  
Д.Г. Алипа ◽  
В.В. Краснов ◽  
В.М. Минненбаев ◽  
А.В. Редька ◽  
Ю.В. Федоров
Keyword(s):  
Remote Sensing ◽  
Gallium Nitride ◽  
Millimeter Wave ◽  
Low Noise ◽  
Low Noise Amplifiers ◽  
Cryogenic Temperatures ◽  
Space Systems ◽  
Earth Remote Sensing ◽  
Hydrogen Level

В статье представлены результаты исследования возможности применения при криогенных температурах водородного уровня дискретных приборов и монолитных схем на основе нитрида галлия в составе малошумящих усилителей сантиметрового и миллиметрового диапазона длин волн для приемных устройств систем дистанционного зондирования Земли из космоса и в составе криогенных комплексов наблюдения космического пространства. The article presents the results of the research on the possibility of using discrete devices and gallium nitride monolithic circuits at the cryogenic temperatures of hydrogen level as part of low-noise amplifiers of centimeter and millimeter-wave bands used in receivers of Earth remote sensing space systems and in cryogenic systems for space observation.

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