1,721,095 research outputs found
A stand-alone a priori profile generation tool for GGG2014 release
No full textThe Total Carbon Column Observing Network (TCCON) is a network of ground-based Fourier Transform Spectrometers that record direct solar absorption spectra of the atmosphere in the near-infrared. From these spectra, accurate and precise column-averaged abundances of atmospheric constituents including CO2, CH4, N2O, HF, CO, H2O, and HDO, are retrieved. This is a stand-alone a priori profile generation tool for the GGG2014 data release.Contact person: Wunch, Debra [email protected]
GTA Bike Surveys August 10-18, 2017
No full textThese are preliminary, uncalibrated, synchronized data from the University of Toronto LGR multigas analyser and Airmar weather station while transported in a bike cargo trailer. These measurements were taken throughout the GTA on 3 surveys: August 10, 15, and 18, 2017
GTA LGR/AMR Truck Campaign July 24 - August 4, 2017
No full textThese are preliminary, uncalibrated, synchronized data from the University of Toronto LGR multigas analyser and Airmar weather station while aboard the Risk Lab survey truck. These measurements were taken throughout the GTA on 9 surveys between July 24, 2017 and August 4, 201
Measuring Methane Emissions in the Urban Environment
No full textMitigating methane (CH4 ) emissions is a necessary intervention to address the immediate impacts of anthropogenic climate change. Bottom-up inventories and models are used to predict the quantity of CH4 emissions, but these estimates are poorly constrained, especially on a source-by-source basis. Measuring CH4 atmospheric concentrations enables direct estimation of emissions rates, and allows for the direct monitoring of the efficacy of emissions mitigation interventions. Within the GreaterToronto Area (GTA), high resolution CH4 inventories predict that anthropogenic CH4 comprises the majority of emissions, primarily from landfills. Atmospheric measurements of CH4 were conducted to quantify emissions from sources in the GTA and throughout Southern Ontario.
Within the GTA, a network of solar-viewing Fourier transform infrared (FTIR) spectrometers was used to quantify the total column dry air mole fractions of CH4 and other greenhouse gases (GHG). This network was expanded to five semi-permanent observatory sites and operated to measure emissions coming from the GTA. In order to confirm, quantify, and discover new sources of CH4 emissions in the GTA, a bicycle-based mobile in situ measurement laboratory was deployed
to measure CH4 concentrations downwind of sources in the city. These measurements were used to quantify emissions from various urban CH4 sources.
Over 650 downwind transects of solid waste and water resource recovery facilities (WRRFs) were used to quantify CH4 emissions from the waste sector in Southern Ontario. From these measurements, solid waste emissions in the GTA in bottom-up inventories were shown to be overestimated. These data were used to investigate correlations between emissions and predictive variables such as meteorological variability for landfills, and volume of treated water for WRRFs.
At a large, active landfill facility in Southern Ontario, six different emissions quantification technologies were compared. This study demonstrates that each technology was capable of quantifying emissions from this facility, and that their average measured emission rates all agreed within uncertainty. Lower measured emissions rates were observed from the ground-based in situ methodologies, and possible explanations for these differences are explored. Implications for monitoring Canadian landfill emissions are discussed with respect to the demonstrated detection limits of these technologies.Ph.D
Exploring Whether City-Level Climate Action Is Correlated with Greater Ambition & Progress Towards National Climate Targets
Full text linkAddressing climate change is a challenge requiring global collaboration, and cities are increasingly recognized as key players in this effort. This thesis investigates whether city-level climate action correlates with greater national emissions reduction progress and target ambition. Focusing on 97 C40 cities and 194 Paris Agreement signatory countries, this study examines GHG emissions levels, standardizes diverse national targets (NDCs), and explores links between local climate initiatives and national outcomes. Results show that C40 cities achieve greater absolute and per-capita emissions reduction than non-C40 cities globally. Likewise, in Europe, North America and Oceania, countries with C40 cities also recorded greater emissions reductions than those without. Further, countries with more ambitious climate targets achieved greater progress in reducing emissions. This research addresses a major gap in climate discourse by highlighting how climate-engaged cities are rising to the challenge and may catalyze greater climate action and ambition at the national level and beyond.ME
Quantifying Methane Emissions from the Greater Toronto Area
Full text linkThe government of Ontario has committed to reduce its greenhouse gas (GHG) emissions by 30% of2005 levels by 2030. The Greater Toronto Area (GTA, pop. 6.4 million) is the most populous city in
Canada, thus accurately quantifying GHG emissions from the GTA is an important step towards meeting
Ontario’s commitments. In order to quantify GHG emissions and emission trends in an urban area, it
is important to monitor GHG concentration levels in the atmosphere regularly to verify the accuracy of
the reported emissions.
In this study, I develop a new methane (CH4) emission inventory, using individual facility reports and
emission estimates from area sources gathered for each municipality in the GTA. This allows us to have
an emission inventory with a high spatial resolution that can be evaluated by atmospheric measurements.
I describe the development of a network of portable Fourier Transform Spectrometers (FTS) in the
GTA that measure total columns of CO2, CH4 and CO in the atmosphere and use the tracer-tracer ratio
method to estimate CH4 emissions in the GTA.
In addition, I preform a detailed assessment of the FTS instrument accuracy, precision and their
optical stability using data collected during a field campaign at 6 TCCON stations in North America.
I also demonstrate that the low-resolution FTSs could be useful as a “travelling standard” to indirectly
compare TCCON instruments to each other. Coincident measurements of the vertical profile of CO2,
CH4, and CO from the AirCore balloon platform provided the data required to tie the FTS retrievals to
the WMO trace gas standard scale so that they can be used as a satellite validation tool.Ph.D
Heat Inequity and Community Vulnerability in Toronto
No full textThe urban heat island (UHI) effect is known to manifest unevenly throughout the built environment, often seen disproportionately affecting marginalized communities across North American cities. These heat inequities arise from the uneven socio-environmental conditions that structure life within urban spatial configurations. Heat inequity in Toronto is seen through positive correlations between summertime land surface temperature (LST) anomalies and the various Ontario Marginalization Index (ON-Marg) dimensions. In Toronto, some heat inequities are only visible at the district level yet remain invisible when considered at the municipal scale. Urban greenspace has been shown to have a negative relationship to a neighbourhood’s LST. Greenspace in Toronto, as measured using the solar induced chlorophyll fluorescence (SIF) product and the City of Toronto’s tree canopy coverage dataset, is shown to have similar negative relationships with LST on the census tract level. Therefore, additions of greenspace in Toronto can help mitigate existing heat inequities. Additional greenspace can lower neighbourhood-level heat in areas that experience elevated temperatures and low access to cooling amenities. From this study, its recommended that further action be taken by the City of Toronto to mitigate existing urban heat inequities, to which the increased equitable distribution of greenspace and changes to the Toronto heat relief network can be major drivers of positive societal change.ME
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Measurements of Greenhouse Gases from Near-infrared Solar Absorption Spectra
Full text linkThis thesis presents improvements to retrievals of greenhouse gas concentrations, with a focus on CO2 and the Arctic.
Near-infrared solar absorption spectra were collected at the Polar Environment Research Laboratory (PEARL) in Eureka, Nunavut as part of the Total Carbon Column Observing Network (TCCON), extending the data record to July 2020. Data processing was improved by the application of solar zenith angle corrections to account for pointing offsets of the solar tracker. Issues related to surface pressure records were resolved. TCCON measurements were used to validate simulations of CO2 and CH4 by GEM-MACH-GHG, a model in development at Environment and Climate Change Canada.
Vertical profile retrievals of CO2 from TCCON spectra were evaluated, using improved spectroscopy and line shapes. CO2 profiles were obtained from sequential retrievals in five spectral windows using synthetic and real spectra. A sensitivity study showed that the leading source of uncertainty in the retrieved CO2 profiles is errors in the a priori temperature profile as small as 2°C between 600-850 hPa. To distinguish the effect of errors in the instrument alignment and spectroscopic parameters from other error sources, CO2 profiles were retrieved using an a prioriprofile built from coincident in-situ measurements. With real spectra, the deviations in retrieved CO2 profiles were larger than typical vertical variations of CO2. Remaining errors in the forward iiimodel limit the accuracy of the retrieved profiles. Implementing a temperature retrieval or correction is critical to improve CO2 profile retrievals.
A study was conducted in support of the proposed Canadian satellite mission AIM-North. The ReFRACtor algorithm was adapted to generate synthetic spectra for a Fourier transform spectrometer and a grating spectrometer. Retrievals were performed on these synthetic spectra to estimate the precision and accuracy of retrieved XCH4, XCO, and XCO2, in different conditions.Over a standard scene corresponding to a boreal forest, the retrieval precision for the given instrument characteristics was ~0.6% for XCH4, ~8% for XCO, and ~0.4% for XCO2. These results can be used by the AIM-North team to decide whether the instrument design should be adapted to meet the mission’s precision and accuracy goals and thresholds over specific scenes.Ph.D
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