scholarly journals Near-infrared remote sensing of Los Angeles trace gas distributions from a mountaintop site

2014 ◽  
Vol 7 (3) ◽  
pp. 713-729 ◽  
Author(s):  
D. Fu ◽  
T. J. Pongetti ◽  
J.-F. L. Blavier ◽  
T. J. Crawford ◽  
K. S. Manatt ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Los Angeles ◽  
Greenhouse Gases ◽  
Near Infrared ◽  
Global Climate ◽  
Ghg Emissions ◽  
Anthropogenic Source ◽  
Los Angeles Basin ◽  
Remote Sensing Technique ◽  
Novel Approach

Abstract. The Los Angeles basin is a significant anthropogenic source of major greenhouse gases (CO2 and CH4) and the pollutant CO, contributing significantly to regional and global climate change. We present a novel approach for monitoring the spatial and temporal distributions of greenhouse gases in the Los Angeles basin using a high-resolution spectroscopic remote sensing technique. A new Fourier transform spectrometer called CLARS-FTS has been deployed since May, 2010, at Jet Propulsion Laboratory (JPL)'s California Laboratory for Atmospheric Remote Sensing (CLARS) on Mt. Wilson, California, for automated long-term measurements of greenhouse gases. The instrument design and performance of CLARS-FTS are presented. From its mountaintop location at an altitude of 1673 m, the instrument points at a programmed sequence of ground target locations in the Los Angeles basin, recording spectra of reflected near-IR solar radiation. Column-averaged dry-air mole fractions of greenhouse gases (XGHG) including XCO2, XCH4, and XCO are retrieved several times per day for each target. Spectra from a local Spectralon® scattering plate are also recorded to determine background (free tropospheric) column abundances above the site. Comparisons between measurements from LA basin targets and the Spectralon® plate provide estimates of the boundary layer partial column abundances of the measured species. Algorithms are described for transforming the measured interferograms into spectra, and for deriving column abundances from the spectra along with estimates of the measurement precision and accuracy. The CLARS GHG measurements provide a means to infer relative, and possibly absolute, GHG emissions.

scholarly journals Near-infrared remote sensing of Los Angeles trace gas distributions from a mountaintop site

2013 ◽  
Vol 6 (5) ◽  
pp. 8807-8854
Author(s):  
D. Fu ◽  
T. J. Pongetti ◽  
J.-F. L. Blavier ◽  
T. J. Crawford ◽  
K. S. Manatt ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Los Angeles ◽  
Greenhouse Gases ◽  
Near Infrared ◽  
Global Climate ◽  
Ghg Emissions ◽  
Anthropogenic Source ◽  
Los Angeles Basin ◽  
Remote Sensing Technique ◽  
Novel Approach

Abstract. The Los Angeles basin is a significant anthropogenic source of major greenhouse gases (CO2 and CH4) and the pollutant CO, contributing significantly to regional and global climate change. We present a novel approach for monitoring the spatial and temporal distributions of greenhouse gases in the Los Angeles basin using a high-resolution spectroscopic remote sensing technique. A new Fourier Transform Spectrometer called CLARS-FTS has been deployed since May 2010 at JPL's California Laboratory for Atmospheric Remote Sensing (CLARS) on Mt. Wilson, California for automated long-term measurements of greenhouse gases. The instrument design and performance of CLARS-FTS are presented. From its mountaintop location at an altitude of 1673 m, the instrument points at a programmed sequence of ground target locations in the Los Angeles basin, recording spectra of reflected near-IR solar radiation. Column-averaged dry-air mole fractions of greenhouse gases (XGHG) including XCO2, XCH4, and XCO are retrieved several times per day for each target. Spectra from a local Spectralon® scattering plate are also recorded to determine background (free tropospheric) column abundances above the site. Comparisons between measurements from LA basin targets and the Spectralon® plate provide estimates of the boundary layer partial column abundances of the measured species. Algorithms are described for transforming the measured interferograms into spectra, and for deriving column abundances from the spectra along with estimates of the measurement precision and accuracy. The CLARS GHG measurements provide a means to infer relative, and possibly absolute, GHG emissions.

scholarly journals Monthly trends of methane emissions in Los Angeles from 2011 to 2015 inferred by CLARS-FTS observations

2016 ◽  
Vol 16 (20) ◽  
pp. 13121-13130 ◽  
Author(s):  
Clare K. Wong ◽  
Thomas J. Pongetti ◽  
Tom Oda ◽  
Preeti Rao ◽  
Kevin R. Gurney ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Los Angeles ◽  
Near Infrared ◽  
Late Summer ◽  
Methane Emissions ◽  
Los Angeles Basin ◽  
Top Down ◽  
Time Period ◽  
Infrared Remote Sensing ◽  
Early Fall

Abstract. This paper presents an analysis of methane emissions from the Los Angeles Basin at monthly timescales across a 4-year time period – from September 2011 to August 2015. Using observations acquired by a ground-based near-infrared remote sensing instrument on Mount Wilson, California, combined with atmospheric CH4–CO2 tracer–tracer correlations, we observed −18 to +22 % monthly variability in CH4 : CO2 from the annual mean in the Los Angeles Basin. Top-down estimates of methane emissions for the basin also exhibit significant monthly variability (−19 to +31 % from annual mean and a maximum month-to-month change of 47 %). During this period, methane emissions consistently peaked in the late summer/early fall and winter. The estimated annual methane emissions did not show a statistically significant trend over the 2011 to 2015 time period.

scholarly journals Monthly trends of methane emissions in Los Angeles from 2011 to 2015 inferred by CLARS-FTS observations

2016 ◽  
Author(s):  
Kam W. Wong ◽  
Thomas J. Pongetti ◽  
Tom Oda ◽  
Preeti Rao ◽  
Kevin. R. Gurney ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Los Angeles ◽  
Near Infrared ◽  
Late Summer ◽  
Methane Emissions ◽  
Los Angeles Basin ◽  
Top Down ◽  
Time Period ◽  
Infrared Remote Sensing ◽  
Early Fall

Abstract. This paper presents an analysis of methane emissions from the Los Angeles basin at monthly timescales across a four-year time period – from September 2011 to August 2015. Using observations acquired by a ground-based near-infrared remote sensing instrument on Mount Wilson, California combined with atmospheric CH4-CO2 tracer-tracer correlations, we observed −18 % to +22 % monthly variability in CH4:CO2 from the annual mean in the Los Angeles basin. Top-down estimates of methane emissions for the basin also exhibit significant monthly variability (−19 % to +31 % from annual mean and a maximum month-to-month change of 47 %). During this period, methane emissions consistently peaked in the late summer/early fall and winter. The estimated annual methane emissions did not show a statistically significant trend over the 2011 to 2015 time period.

Toward CO2 and CH4 measurements by ground-based observations of surface-scattered sunlight

2021 ◽  
Author(s):  
Benedikt Hemmer ◽  
Christin Proß ◽  
Stanley P. Sander ◽  
Thomas J. Pongetti ◽  
Zhao-Cheng Zeng ◽  
...  
Keyword(s):  
Los Angeles ◽  
Urban Areas ◽  
Near Infrared ◽  
Chem Phys ◽  
Retrieval Algorithm ◽  
Los Angeles Basin ◽  
Satellite Measurements ◽  
Precise Knowledge ◽  
Extended Sources

<div> <div>Precise knowledge of sources and sinks in the carbon cycle is desired to understand its sensitivity to climate change and to account and verify man-made emissions. In this context, extended sources like urban areas play an important role. While in-situ measurements of carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>) are highly accurate but localized, satellites measure column-integrated concentrations over an extended footprint. The CLARS-FTS [1, 2] stationed at the Mt. Wilson observatory looking downward into the Los Angeles basin has pioneered an innovative measurement technique that fills the sensitivity gap between in-situ and satellite measurements. The technique enables mapping the urban greenhouse gas concentration fields by collecting spectra of ground scattered sunlight and scanning through the region.</div> <div> </div> <div>Here, we report on progress developing a portable setup for a CLARS-FTS-like measurement geometry. The instrument is based on the EM27/SUN FTS with a modified pointing technique and a more sensitive detector. The retrieval algorithm is based on the RemoTeC software, previously employed for solar backscatter satellite measurements. We discuss first steps in terms of instrument performance and retrieval exercises. For the latter, we have carried out simulations on how the neglect of scattering by the retrieval affects the retrieved boundary layer concentrations of CO<sub>2</sub> and CH<sub>4</sub> for an ensemble of hypothetical scenes with variable complexity in aeorsol loadings and viewing geometry. We also report on a test to apply RemoTeC to a small set of CLARS-FTS spectra collected throughout the Los Angeles basin.</div> <div> </div> <div><em>References</em></div> <div>[1] Fu, D. et al., 2014: Near-infrared remote sensing of Los Angeles trace gas distributions from a mountaintop site, Atmos. Meas. Tech., 7, 713–729, https://doi.org/10.5194/amt-7-713-2014</div> [2] Wong, K. W. et al., 2015: Mapping CH4 : CO2 ratios in Los Angeles with CLARS-FTS from Mount Wilson, California, Atmos. Chem. Phys., 15, 241–252, https://doi.org/10.5194/acp-15-241-2015</div>

scholarly journals GFIT3: a full physics retrieval algorithm for remote sensing of greenhouse gases in the presence of aerosols

2021 ◽  
Vol 14 (10) ◽  
pp. 6483-6507
Author(s):  
Zhao-Cheng Zeng ◽  
Vijay Natraj ◽  
Feng Xu ◽  
Sihe Chen ◽  
Fang-Ying Gong ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Los Angeles ◽  
Greenhouse Gases ◽  
High Spectral Resolution ◽  
Ratio Method ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Atmospheric Scattering ◽  
Aerosol Scattering ◽  
The Impact

Abstract. Remote sensing of greenhouse gases (GHGs) in cities, where high GHG emissions are typically associated with heavy aerosol loading, is challenging due to retrieval uncertainties caused by the imperfect characterization of scattering by aerosols. We investigate this problem by developing GFIT3, a full physics algorithm to retrieve GHGs (CO2 and CH4) by accounting for aerosol scattering effects in polluted urban atmospheres. In particular, the algorithm includes coarse- (including sea salt and dust) and fine- (including organic carbon, black carbon, and sulfate) mode aerosols in the radiative transfer model. The performance of GFIT3 is assessed using high-spectral-resolution observations over the Los Angeles (LA) megacity made by the California Laboratory for Atmospheric Remote Sensing Fourier transform spectrometer (CLARS-FTS). CLARS-FTS is located on Mt. Wilson, California, at 1.67 km a.s.l. overlooking the LA Basin, and it makes observations of reflected sunlight in the near-infrared spectral range. The first set of evaluations are performed by conducting retrieval experiments using synthetic spectra. We find that errors in the retrievals of column-averaged dry air mole fractions of CO2 (XCO2) and CH4 (XCH4) due to uncertainties in the aerosol optical properties and atmospheric a priori profiles are less than 1 % on average. This indicates that atmospheric scattering does not induce a large bias in the retrievals when the aerosols are properly characterized. The methodology is then further evaluated by comparing GHG retrievals using GFIT3 with those obtained from the CLARS-GFIT algorithm (used for currently operational CLARS retrievals) that does not account for aerosol scattering. We find a significant correlation between retrieval bias and aerosol optical depth (AOD). A comparison of GFIT3 AOD retrievals with collocated ground-based observations from AErosol RObotic NETwork (AERONET) shows that the developed algorithm produces very accurate results, with biases in AOD estimates of about 0.02. Finally, we assess the uncertainty in the widely used tracer–tracer ratio method to obtain CH4 emissions based on CO2 emissions and find that using the CH4/CO2 ratio effectively cancels out biases due to aerosol scattering. Overall, this study of applying GFIT3 to CLARS-FTS observations improves our understanding of the impact of aerosol scattering on the remote sensing of GHGs in polluted urban atmospheric environments. GHG retrievals from CLARS-FTS are potentially complementary to existing ground-based and spaceborne observations to monitor anthropogenic GHG fluxes in megacities.

scholarly journals The Evolution of NEPA in the Fight Against Climate Change

2011 ◽  
Vol 5 ◽  
Author(s):  
Robert Reiley
Keyword(s):  
Climate Change ◽  
Forest Management ◽  
Los Angeles ◽  
Global Climate ◽  
Ghg Emissions ◽  
The United States ◽  
National Environmental Policy Act ◽  
Outer Continental Shelf ◽  
Wide Range ◽  
National Environmental

The National Environmental Policy Act (“NEPA”) is the first environmental charter of the United States. 1 Signed into law on January 1, 1970, NEPA addresses the need for overarching national environmental guidance in the country. During the course of its forty year history, NEPA has been used to challenge a wide range of federal actions including the issuance of operating permits under the Clean Air Act,2 the approval of forest management plans approved under the National Forest Management Act,3 the construction of highways under the Federal-Aid Highways Act,4 and the issuance of oil leases under the Outer Continental Shelf Lands Act.5 Given the breadth of NEPA’s applicability, it was inevitable that NEPA would become a tool to combat climate change. The use of NEPA to require federal agencies to take a “hard look” at greenhouse gas (“GHG”) emissions makes perfect sense because many federal actions directly or indirectly contribute to GHG emissions. Since 1990, in City of Los Angeles v. NHTSA,6 plaintiffs have used NEPA, successfully and unsuccessfully, to challenge federal actions that might have an impact on the global climate.

scholarly journals Using ocean-glint scattered sunlight as a diagnostic tool for satellite remote sensing of greenhouse gases

2013 ◽  
Vol 6 (3) ◽  
pp. 4371-4400
Author(s):  
A. Butz ◽  
S. Guerlet ◽  
O. P. Hasekamp ◽  
A. Kuze ◽  
H. Suto
Keyword(s):  
Remote Sensing ◽  
Greenhouse Gases ◽  
Satellite Remote Sensing ◽  
Near Infrared ◽  
Ocean Surface ◽  
Absorption Bands ◽  
Error Sources ◽  
Carbon Dioxide Co2 ◽  
Source Of Error ◽  
Better Than

Abstract. Spectroscopic measurements of sunlight backscattered by the Earth's surface is a technique widely used for remote sensing of atmospheric constituent concentrations from space. Thereby, remote sensing of greenhouse gases poses particularly challenging accuracy requirements for instrumentation and retrieval algorithms which, in general, suffer from various error sources. Here, we investigate a method that helps disentangle sources of error for observations of sunlight backscattered from the glint spot on the ocean surface. The method exploits the backscattering characteristics of the ocean surface which is bright for glint geometry but dark for off-glint angles. This property allows for identifying a set of clean scenes where light scattering due to particles in the atmosphere is negligible such that uncertain knowledge of the lightpath can be excluded as a source of error. We apply the method to more than 3 yr of ocean-glint measurements by the Thermal And Near infrared Sensor for carbon Observation (TANSO) – Fourier Transform Spectrometer (FTS) onboard the Greenhouse Gases Observing Satellite (GOSAT) which aims at measuring carbon dioxide (CO2) and methane (CH4) concentrations. The proposed method is able to clearly monitor recent improvements in the instrument calibration of the oxygen (O2) A-band channel and suggests some residual uncertainty in our knowledge about the instrument. We further assess the consistency of CO2 retrievals from several absorption bands between 6400 cm−1 (1565 nm) and 4800 cm−1 (2100 nm) and find that the absorption bands commonly used for monitoring of CO2 dry air mole fractions from GOSAT allow for consistency better than 1.5 ppm. Usage of other bands reveals significant inconsistency among retrieved CO2 concentrations pointing at inconsistency of spectroscopic parameters.

scholarly journals GFIT3: A full physics retrieval algorithm for remote sensing of greenhouse gases in the presence of aerosols

2021 ◽  
Author(s):  
Zhao-Cheng Zeng ◽  
Vijay Natraj ◽  
Feng Xu ◽  
Sihe Chen ◽  
Fang-Ying Gong ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Los Angeles ◽  
Greenhouse Gases ◽  
High Spectral Resolution ◽  
Ratio Method ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Atmospheric Scattering ◽  
Aerosol Scattering ◽  
The Impact

Abstract. Remote sensing of greenhouse gases (GHGs) in cities, where high GHG emissions are typically associated with heavy aerosol loading, is challenging due to retrieval uncertainties caused by imperfect characterization of scattering by aerosols. We investigate this problem by developing GFIT3, a full physics algorithm to retrieve GHGs (CO2 and CH4) by accounting for aerosol scattering effects in polluted urban atmospheres. In particular, the algorithm includes coarse (including sea salt and dust) and fine (including organic carbon, black carbon, and sulfate) mode aerosols in the radiative transfer model. The performance of GFIT3 is assessed using high spectral resolution observations over the Los Angeles (LA) megacity made by the California Laboratory for Atmospheric Remote Sensing–Fourier Transform Spectrometer (CLARS–FTS). CLARS–FTS is located on Mt. Wilson, California, at 1.67 km a.s.l. overlooking the LA basin, and makes observations of reflected sunlight in the near-infrared spectral range. The first set of evaluations are performed by conducting retrieval experiments using synthetic spectra. We find that errors in the retrievals of column-averaged dry air mole fractions of CO2 (XCO2) and CH4 (XCH4) due to uncertainties in the aerosol optical properties and atmospheric a priori profiles are less than 1 % on average. This indicates that atmospheric scattering does not induce a large bias in the retrievals when the aerosols are properly characterised. The methodology is then further evaluated by comparing GHG retrievals using GFIT3 with those obtained from the CLARS-GFIT algorithm (used for currently operational CLARS retrievals) that does not account for aerosol scattering. We find a significant correlation between retrieval bias and aerosol optical depth (AOD). Comparison of GFIT3 AOD retrievals with collocated ground-based observations from AERONET shows that the developed algorithm produces very accurate results, with biases in AOD estimates of about 0.02. Finally, we assess the uncertainty in the widely used tracer-tracer ratio method to obtain CH4 emissions based on CO2 emissions, and find that using the CH4 / CO2 ratio effectively cancels out biases due to aerosol scattering. Overall, this study of applying GFIT3 to CLARS-FTS observations improves our understanding of the impact of aerosol scattering on the remote sensing of GHGs in polluted urban atmospheric environments. GHG retrievals from CLARS-FTS are potentially complementary to existing ground-based and space-borne observations to monitor anthropogenic GHG fluxes in megacities.

Coastline Detection from Remote Sensing Image Based on K-Mean Cluster and Distance Transform Algorithm

2013 ◽  
Vol 760-762 ◽  
pp. 1567-1571 ◽  
Author(s):  
Ying Liu
Keyword(s):  
Remote Sensing ◽  
Cluster Algorithm ◽  
Remote Sensing Image ◽  
Distance Transform ◽  
Land Area ◽  
Remote Sensing Technique ◽  
Novel Approach ◽  
Sea Area

Using remote sensing technique to determine coastline's position has been received vital attention. This paper presents a novel approach for detecting coastline of remote sensing image based on K-Means cluster and Distance Transform algorithm. K-Means cluster algorithm divides the image into two regions-water and land area. Then to extract the sea area by distance transfoming. Finally, the coastline will be detected by edge traking. Results showed that the method proposed in this paper have good performance in accuracy and completeness.

scholarly journals Mapping CH<sub>4</sub> : CO<sub>2</sub> ratios in Los Angeles with CLARS-FTS from Mount Wilson, California

2015 ◽  
Vol 15 (1) ◽  
pp. 241-252 ◽  
Author(s):  
K. W. Wong ◽  
D. Fu ◽  
T. J. Pongetti ◽  
S. Newman ◽  
E. A. Kort ◽  
...  
Keyword(s):  
Los Angeles ◽  
Emission Inventory ◽  
Near Infrared ◽  
Anthropogenic Activities ◽  
Ghg Emissions ◽  
High Sensitivity ◽  
The United States ◽  
Ch4 Emission ◽  
Bottom Up ◽  
Spatiotemporal Trends

Abstract. The Los Angeles megacity, which is home to more than 40% of the population in California, is the second largest megacity in the United States and an intense source of anthropogenic greenhouse gases (GHGs). Quantifying GHG emissions from the megacity and monitoring their spatiotemporal trends are essential to be able to understand the effectiveness of emission control policies. Here we measure carbon dioxide (CO2) and methane (CH4) across the Los Angeles megacity using a novel approach – ground-based remote sensing from a mountaintop site. A Fourier transform spectrometer (FTS) with agile pointing optics, located on Mount Wilson at 1.67 km above sea level, measures reflected near-infrared sunlight from 29 different surface targets on Mount Wilson and in the Los Angeles megacity to retrieve the slant column abundances of CO2, CH4 and other trace gases above and below Mount Wilson. This technique provides persistent space- and time-resolved observations of path-averaged dry-air GHG concentrations, XGHG, in the Los Angeles megacity and simulates observations from a geostationary satellite. In this study, we combined high-sensitivity measurements from the FTS and the panorama from Mount Wilson to characterize anthropogenic CH4 emissions in the megacity using tracer–tracer correlations. During the period between September 2011 and October 2013, the observed XCH4 : XCO2 excess ratio, assigned to anthropogenic activities, varied from 5.4 to 7.3 ppb CH4 (ppm CO2)−1, with an average of 6.4 ± 0.5 ppb CH4 (ppm CO2)−1 compared to the value of 4.6 ± 0.9 ppb CH4 (ppm CO2)−1 expected from the California Air Resources Board (CARB) bottom-up emission inventory. Persistent elevated XCH4 : XCO2 excess ratios were observed in Pasadena and in the eastern Los Angeles megacity. Using the FTS observations on Mount Wilson and the bottom-up CO2 emission inventory, we derived a top-down CH4 emission of 0.39 ± 0.06 Tg CH4 year−1 in the Los Angeles megacity. This is 18–61% larger than the state government's bottom-up CH4 emission inventory and consistent with previous studies.

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