| 1. |
- Eliasson, Ingegärd, 1961, et al.
(författare)
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Wind fields and turbulence statistics in an urban street canyon
- 2006
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 40:1, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- This is the first paper of a long-term measurement campaign to explore wind, temperature, radiation and energy fieldswithin an urban canyon. A canyon and a rooftop mast were installed in a canyon with an aspect ratio (Height/Width)of 2.1 in Goteborg, Sweden. A number of instruments including sonic anemometers, radiometers and thermocoupleswere mounted in vertical profiles and across the width of the canyon. The experimental set-up, the characteristics of thecanyon flow pattern and mean and turbulence statistics with respect to above canyon flow are examined using datacollected under clear-sky conditions in summer and autumn 2003. Results show that under cross-canyon (within 601 oforthogonal) flow, a single helical vortex exists. High temporal resolution analysis suggests that eddies frequentlypenetrate the shear stress layer at the canyon top disrupting established flow patterns. A combination of complexbuilding roof shapes and local topography may contribute to this effect by maintaining a high degree of turbulence. Theprofile of mean wind speed within the canyon and the relation with that above canyon depends on the ambient flowdirection in relation to the canyon long axis. Turbulence statistics show results similar to other field studies, withturbulence kinetic energy and vertical mixing greatest toward the windward wall.
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| 2. |
- Erell, Evyatar, et al.
(författare)
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The effect of stability on estimated variations of advected moisture in the Canyon Air Temperature (CAT) model
- 2010
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Ingår i: Ninth Symposium on the Urban Environment. ; :J4C.4
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Konferensbidrag (refereegranskat)abstract
- CAT (Canyon Air Temperature) is a parametric model that predicts site-specific air temperature in an urban street canyon for extended periods on the basis of data from a reference station in the region. A method is described for incorporating spatial and temporal variations in advected moisture, allowing application of the model with no prior knowledge of moisture availability in the area. The revised model is tested against data from field experiments in Gothenburg and Adelaide, in all seasons and in a variety of atmospheric conditions. Moisture availability is determined by site surface cover only in super-stable conditions and in the absence of wind. In other weather conditions, the effect of stability on advection from more distant source areas is weak.
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| 3. |
- Evyatar, E, et al.
(författare)
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Incorporating spatial and temporal variations of advected moisture in the canyon air temperature (CAT) model.
- 2009
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Ingår i: ICUC7 Proceedings.
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Konferensbidrag (refereegranskat)abstract
- CAT (Canyon Air Temperature) is a parametric model that predicts site-specific air temperature in an urban street canyon for extended periods on the basis of data from a reference station in the region. A method is described for incorporating spatial and temporal variations in advected moisture, allowing application of the model with no prior knowledge of moisture availability in the area. The revised model is tested against data from field experiments in Gothenburg and Adelaide, in all seasons and in a variety of atmospheric conditions.
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| 4. |
- Johansson, John, 1982, et al.
(författare)
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Emission measurements of alkenes, alkanes, SO2, and NO2 from stationary sources in Southeast Texas over a 5 year period using SOF and mobile DOAS
- 2014
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202 .- 2169-897X. ; 119:4, s. 1973-1991
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Tidskriftsartikel (refereegranskat)abstract
- A mobile platform for flux measurements of VOCs (alkanes and alkenes), SO2, and NO2 emissions using the Solar Occultation Flux (SOF) method and mobile differential optical absorption spectroscopy (DOAS) was used in four different studies to measure industrial emissions. The studies were carried out in several large conglomerates of oil refineries and petrochemical industries in Southeast and East Texas in 2006, 2009, 2011, and 2012. The measured alkane emissions from the Houston Ship Channel (HSC) have been fairly stable between 2006 and 2011, averaging about 11,500kg/h, while the alkene emissions have shown greater variations. The ethene and propene emissions measured from the HSC were 1511kg/h and 878kg/h, respectively, in 2006, while dropping to roughly 600kg/h for both species in 2009 and 2011. The results were compared to annual inventory emissions, showing that measured VOC emissions were typically 5-15 times higher, while for SO2 and NO2 the ratio was typically 0.5-2. AP-42 emission factors were used to estimate meteorological effects on alkane emissions from tanks, showing that these emissions may have been up to 35-45% higher during the studies than the annual average. A more focused study of alkene emissions from a petrochemical complex in Longview in 2012 identified two upset episodes, and the elevation of the total emissions during the measurement period due to the upsets was estimated to be approximately 20%. Both meteorological and upset effects were small compared to the factor of 5-15, suggesting that VOC emissions are systematically and substantially underestimated in current emission inventories.
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| 5. |
- Johansson, John, 1982, et al.
(författare)
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Quantitative measurements and modeling of industrial formaldehyde emissions in the Greater Houston area during campaigns in 2009 and 2011
- 2014
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 119:7, s. 4303-4322
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Tidskriftsartikel (refereegranskat)abstract
- A sensitive Mobile differential optical absorption spectroscopy (DOAS) system with real-time evaluation capability and HCHO detection limit of 3 ppb over 100 m has been developed. The system was operated together with a Solar Occultation Flux system for large-scale vertical flux measurements of HCHO, NO2, SO2, and VOCs in the Houston-Galveston-Brazoria area during two studies, in 2009 (Study of Houston Atmospheric Radical Precursors campaign) and in 2011 (Air Quality Research Program study). Both in 2009 and 2011, HCHO plumes from five separate local sources in Texas City, Mont Belvieu, and Houston Ship Channel (HSC) were repeatedly detected using Mobile DOAS with emissions varying between 6 and 40 kg/h. In many cases significant alkene emissions were detected simultaneously with the HCHO plumes. Furthermore, in 2011 two additional sources were observed in Texas City and in HSC, with 10 kg/h and 31 kg/h HCHO, respectively. A plume chemistry model was applied to 13 cases to investigate whether the detected HCHO was emitted directly from the industries or was produced by photochemical degradation of VOCs. The model results showed that on average 90% of the detected HCHO was of primary origin and the photochemical production contributed more than 10% in only three cases. Based on the repeatability, it is likely that the most significant HCHO sources in the area are included in this study with an overall emission of 120 kg/h. On a regional scale, this emission is small compared to the secondary HCHO formed from oxidation of reactive VOCs emitted from the same industries, estimated to be an order of magnitude higher.
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| 6. |
- Lordian, Thomas, et al.
(författare)
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Local-Scale Urban Meteorological Parameterization Scheme (LUMPS): longwave radiation parameterization and seasonality related developments
- 2011
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Ingår i: Journal of Applied Meteorology and Climatology. - 1558-8424 .- 1558-8432. ; 50, s. 185-202
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Tidskriftsartikel (refereegranskat)abstract
- Recent developments to the Local-scale Urban Meteorological Parameterization Scheme (LUMPS), a simple model able to simulate the urban energy balance are presented. The major development is the coupling of LUMPS to the Net All-Wave Radiation Parameterization (NARP). Others include that the model now accounts for: changing availability of water at the surface; seasonal variations of active vegetation; and the anthropogenic heat flux; while maintaining the need for only commonly available meteorological observations and basic surface characteristics. The incoming component of the longwave radiation (L↓) in NARP is improved through a simple relation derived using cloud cover observations from a ceilometer collected in central London. The new L↓ formulation is evaluated with two independent multi-year datasets (Łódź, Poland and Baltimore, USA) and compared to alternatives that include: the original NARP and a simpler one using the U. S. National Climatic Data Center cloud observation database as input. The performance for the surface energy balance fluxes is assessed using a two year dataset (Łódź). Results have an overall RMSE
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| 7. |
- Mellqvist, Johan, 1965, et al.
(författare)
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An uncertainty methodology for solar occultation flux measurements: ammonia emissions from livestock production
- 2024
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Ingår i: Atmospheric Measurement Techniques. - 1867-1381 .- 1867-8548. ; 17:8, s. 2465-2479
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Tidskriftsartikel (refereegranskat)abstract
- Ammonia (NH3/ emissions can negatively affect ecosystems and human health, so they should be monitored and mitigated. This study presents methodology for the estimation of uncertainties in NH3 emissions measurements using the solar occultation flux (SOF) method. The reactive nature of NH3 makes its measurement challenging, but SOF offers a reliable open-path passive method which utilizes solar spectrum data, thereby avoiding gas adsorption within the instrument. To compute NH3 gas fluxes, horizontal and vertical wind speed profiles, as well as plume height estimates and spatially resolved column measurements, are integrated. A unique aspect of this work is the first-time description of plume height estimations derived from ground and column NH3 concentration measurements aimed at uncertainty reduction. Initial validation tests indicated measurement errors between -31 % and C14 % on average, which was slightly larger than the estimated expanded uncertainty ranging from ± 12 % to ± 17 %. Application of the methodology to assess emission rates from farms of various sizes showed uncertainties between ± 21 % and ± 37 %, generally influenced by systematic wind uncertainties and random errors. The method demonstrates the capacity to measure NH3 emissions from both small (~ 0.5 1 kg h-1/ and large (~ 100 kg h-1/ sources in high-density farming areas. Generally, the SOF method provided an expanded uncertainty below 30 % in measuring NH3 emissions from livestock production, which could be further improved by adhering to best application practices. This paper s findings offer the potential for broader applications, such as measuring NH3 fluxes from fertilized fields and in the oil and gas sector. However, these applications would require further research to adapt and refine the methodologies for these specific contexts.
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| 8. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Characterization of Air Toxics and Greenhouse Gas Emission Sources and Their Impacts on Community-Scale Air Quality Levels in Disadvantaged Communities
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Methane (CH4) is an important short-lived climate pollutant and contributes roughly 9 percent to California's statewide GHG emissions. California has passed several climate legislations, including AB 1383 (Lara, 2015-16) and AB 1496 (Thurmond, 2015-16), which require CARB to use the best available scientific and technical methods to monitor and measure high-emission CH4 hotspots within the State, to use the information to update relevant programs and policies, and to implement a climate mitigation program to reduce statewide CH4 emissions by 40 percent below the 2013 levels. Furthermore, certain industrial emissions sources of CH4, such as oil and gas facilities, are known to co-emit air toxics that have adverse health effects, and their impacts are more pronounced in communities near those sources than they are regionally. Therefore, it is important to understand these emissions, and conduct enhanced community-scale monitoring for air toxics in near-source communities, many of which may be disadvantaged. Additionally, scientific studies have suggested that national and statewide CH4 emissions inventories may be underestimated, and real-world emissions measurements may be useful to evaluate source-level emission estimates and understand emission behaviors. The objectives of this research study are to characterize air toxics and GHG emission behavior from a variety of complex emission sources, and to study the impact of these sources on air quality levels in disadvantaged communities. The project utilized a state-of-the-art research-grade mobile monitoring laboratory equipped with advanced monitoring instruments to characterize and quantify the air toxics and GHG emission behavior from complex air pollution sources, as well as their air pollution impacts on nearby communities. Through four regional campaigns across California, the project measured facility-level emissions of CH4, alkanes, benzene, BTEX (benzene, toluene, ethylbenzene and xylene), ammonia (NH3), and sulfur and nitrogen oxides (SOX and NOX) from a variety of sources, including refineries, petrochemical facilities, oil storage, port activities, landfills, oil and gas production and dairy farms, and tracked the air pollution impact of the emission plumes in neighboring communities. This study found that the observed emissions, which are representative of emissions at a single point in time, were greater than inventory factors and models, representative of overall averages, for many of the volatile organic compounds (VOC). Alkane emissions from five large refinery areas in the Bay Area were on average 2.5 times the reported emission, and CH4 emissions were roughly 3 times the reported emissions, while total NOX emissions were comparable to the inventory estimates. Similarly, alkane and CH4 emissions from oil and gas fields in the San Joaquin Valley, which accounts for more than 70 percent of California's oil and gas production capacity, were 10 and 2 times higher than production-based emission factors, respectively. On the other hand, CH4 and NH3 emissions from roughly 20 dairy farms were 50 percent and 100 percent higher than annual emission factor, respectively, some of which were due to diurnal variations. These discrepancies suggest more work is needed to ascertain whether these point-in-time measurements are representative of annual averages, and if emissions are indeed higher than standard methods suggest. The measurements in the Richmond community showed VOC concentrations dominated by alkanes from the port area. Community-scale ground-level concentrations of BTEX were on average low in all studies. The research study demonstrated the use of advanced techniques for facility-wide emission measurements and community monitoring of air toxics, and suggests that a combination of mobile and fixed continuous measurements may provide useful information to understand source emissions, and their impacts on communities. The source-level emission data may be useful to understand emissions from complex emission sources (including large point sources, distributed emission sources, area sources). The community-scale measurement effort will provide the ability to conduct community-scale air toxics measurements in real-time, with information on air pollution hotspots in various disadvantaged communities and useful screening information to identify potential sources for prioritizing air pollution mitigation efforts. https://ww3.arb.ca.gov/research/single-project.php?row_id=67028
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| 9. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Measurements of fugitive emissions of vocs from stationary sources using the SOF method - Standardization efforts and results from recent studies in California
- 2019
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Ingår i: AQM 2019 - Air Quality Measurement Methods and Technology Conference 2019.
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Konferensbidrag (refereegranskat)abstract
- The Solar Occultation Flux (SOF) method is used to screen and quantify VOC emissions from industrial conglomerates down to sub-areas in individual plants, such as a few tank process area or water treatment areas. The SOF method has been applied in several larger campaigns in both Europe and in the US (Mexico City 2006, Texas 2006/2009/2011/2012; Le Havre 2008, Rotterdam 2008/2010 and Antwerp 2010/2016, California 2013/20T5, Tianjin China 2016) and in more than 100 individual plant surveys over the world. The technique has been validated by comparison to other methods and tracer gas releases and it typically has an uncertainty of 30%, mostly due to uncertainties in the wind field. In the various campaign studies it has been found that the measured emissions obtained with SOF are 3–10 times higher than the reported emission obtained by calculations. The SOF method is Best Available Technology in Europe for quantitative measurements of diffuse emissions from refineries and the chemical sector. The technique is presently being standardized by the European CEN.
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| 10. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Methane emissions from industrial activities using drones
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Innovative drone-based methods have been developed to map and quantify methane leakages from various industrial activities, such as refineries, Liquified Natural Gas (LNG) terminals, landfills, and water treatment facilities. These methods use a high-speed, high-sensitivity laser sensor and were validated through controlled gas releases. They were also compared to a ground-based infrared absorption-based technique. This initiative is supported by the Swedish Governmental Agency for Innovation Systems (Vinnova) and aligns with UN Sustainable Development Goals 9, 11, and 13. The goal is to reduce methane emissions significantly, aiding Sweden in achieving net-zero greenhouse gas emissions by 2045. Accurate measurements enable effective, targeted, and trackable measures to minimize emissions, resulting in a rapid positive climate impact. The project has led to the development of two distinct drone-based methods: the wall approach and the tracer approach. The wall approach measures gas concentrations across the entire cross-section of the plume, whereas the tracer approach measures the ratio of leaking gas to source gas. Depending on the source's size, one approach may be preferred over the other, with the tracer method being more suitable for point sources and the wall approach for larger sources. The custom-designed drone in this project, provided and operated by Gerdes Solution. is equipped with a high-sensitivity laser sensor and has a flight duration of about 12 minutes while carrying a 3 kg payload. This limitation presents a challenge when conducting wall measurements, which require approximately 25 minutes of flight time for the studied sources. Due to the drone's limited flight time, it necessitates landing and battery replacement, which complicates the process and limits the number of repeat measurements. In future endeavors, employing a drone with a longer flight duration would be advantageous. In total, the study detected about 220 kg/h of methane emissions and 3 kg/h of nitrous oxide emissions, equivalent to an emission rate of about 7 tons/h of carbon dioxide. The emissions were dominated by the water treatment plant and landfills, with relatively little coming from the refinery and LNG plant. However, the wall measurements in thus study serve as demonstrations of how the technique can be used and do not provide a comprehensive picture of the actual emissions from the individual sites; this would require more statistical data in terms of repeat measurements and measurement days. It is shown that drone measurements using the new high sensitivity laser is a valuable tool for mapping methane concentrations from various types of industrial sources, which are challenging to investigate today due to diffuse emissions, large dimensions, and complex geometries. The validation studies show that both the wall approach and controlled tracer releases can be used to quantify emissions, achieving an accuracy of up to 10 % for a simple, single, source. However, in the real measurement situation, the wall approach may be difficult to execute due to practical challenges like flying restrictions and the need for spatially dense data that can be interpolated to a homogenous grid and repeated measurements. In several cases, when the drone had to fly relatively close to the plumes, downwind of large buildings in complex and turbulent wind fields, the wall approach yielded large variability in the resulting flux. It is hence evident that the wall approach requires a thorough understanding of the measurement situation, and that repeated measurements are needed, at different distances from the source and in varying wind directions. The tracer approach was therefore preferred choice for obtaining emission rates in this study, although it is challenging to carry out representative tracer releases for larger sources and for cases when the measurements are performed near to the source, and in this case the wall approach is preferred. It was also shown that the drone-based tracer approach is advantageous to the ground based since it is then easier to capture the full plume.
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| 11. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Mobile optical measurements of emissions and fenceline concentrations from oil and gas production
- 2019
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Ingår i: AQM 2019 - Air Quality Measurement Methods and Technology Conference 2019.
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Konferensbidrag (refereegranskat)abstract
- The mobile measurement platform and optical methods used in the SQAMD project1 allowed for mapping concentrations and measuring fluxes from a large number of sources and source types, and provided very useful information on the relative contribution of small stationary sources to alkane and BTEX emissions in the SCAB. Sources ranged from single oil wells to large tank farms, refineries, and off shore installations. Note that these sources are not subjected to the same regulatory requirements as larger industrial facilities. Future studies aimed at improving the emission estimates in SCAB should include a larger subset of units from all major source categories, and a better characterization of their spatial and temporal variability.
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| 12. |
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| 13. |
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| 14. |
- Offerle, Brian, 1967, et al.
(författare)
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Surface heating in relation to air temperature, wind and turbulence in an urban street canyon
- 2007
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Ingår i: Boundary-Layer Meteorology. - : Springer Science and Business Media LLC. - 0006-8314 .- 1573-1472. ; 122:2, s. 273-292
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Tidskriftsartikel (refereegranskat)abstract
- Wind and temperature measurements from within and above a deep urban canyon (height/width = 2.1) were used to examine the thermal structure of air within the canyon, exchange of heat with the overlying atmosphere, and the possible impacts of surface heating on within-canyon air flow. Measurements were made over a range of seasons and primarily analysed for sunny days. This allowed the study of temperature differences between opposing canyon walls and between wall and air of more than 15 degrees C in summer. The wall temperature patterns follow those of incoming solar radiation loading with a secondary daytime effect from the longwave exchange between the walls. In winter, the canyon walls receive little direct solar radiation, and temperature differences are largely due to anthropogenic heating of the building interiors. Cool air from aloft and heated air from canyon walls is shown to circulate within the canyon under cross-canyon flow. Roofs and some portions of walls heat up rapidly on clear days and have a large influence on heat fluxes and the temperature field. The magnitude and direction of the measured turbulent heat flux also depend strongly on the direction of flow relative to surface heating. However, these spatial differences are smoothed by the shear layer at the canyon top. Buoyancy effects from the heated walls were not seen to have as large an impact on the measured flow field as has been shown in numerical experiments. At night canyon walls are shown to be the source of positive sensible heat fluxes. The measurements show that materials and their location, as well as geometry, play a role in regulating the heat exchange between the urban surface and atmosphere.
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| 15. |
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| 16. |
- Offerle, Brian, 1967, et al.
(författare)
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Urban modification of the surface energy balance in the West African Sahel: Ouagadougou, Burkina Faso
- 2005
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Ingår i: Journal of Climate. - 0894-8755 .- 1520-0442. ; 18:19, s. 3983-3995
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Tidskriftsartikel (refereegranskat)abstract
- Surface-atmosphere energy exchanges in Ouagadougou, Burkina Faso, located in the West African Sahel, were investigated during February 2003. Basic knowledge of the impact of land cover changes on local climate is needed to understand and forecast the impacts of rapid urbanization predicted for the region. Previously collected data showed a large dry season urban heat island (UHI), which dramatically decreased with the onset of the rainy season and corresponding changes to the natural land cover thermal and radiative properties. Observations of local-scale energy balance fluxes were made over a residential district; and building surface temperatures were measured in three separate locations. Net all-wave radiation showed an increase with urbanization owing to the higher albedo, lower heat capacity, and thermal conductivity of the bare dry soil compared to the urbanized surface. The combination of material and geometry resulted in a decrease in albedo toward the urban center. Despite the higher albedo, surface temperatures of bare undisturbed soil could exceed surface temperatures in the residential area and urban center by 15 degrees-20 degrees C due to differences in thermal characteristics. Turbulent heat exchange measured over a residential area was dominated by sensible heat flux. Latent heat fluxes were greater than expected from the amount of vegetation but in accordance with water use in the area. An urban land surface scheme reproduced fluxes in agreement with measurements. The results point toward an intensification of the dry season urban heat island in Ouagadougou, given increased urbanization.
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| 17. |
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| 18. |
- Samuelsson, Jerker, 1972, et al.
(författare)
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Quantification of VOC emissions using tracer dispersion, Mobile Extractive FTIR (MEFTIR) and Mobile Whitecell-DOAS (MWDOAS)
- 2015
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Ingår i: Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA. - 1052-6102. - 9781510815582 ; 3, s. 2310-2317
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Konferensbidrag (refereegranskat)abstract
- The application of Mobile Extractive FTIR and Mobile Whitecell Differential Optical Absorption Spectroscopy to establish VOC emission factors for tank filling operations and for discharge of petroleum products to trucks and vessels is described. An example of VOC emissions related to discharge of gasoline to trucks at a depot, which was connected to vapor recovery unit, is presented. Discharge of gasoline to ships was found to have an alkane (CH4 emission factor of about 5x10-5 kg emitted VOC/kg discharged product, comparable to the corresponding for trucks. This is an abstract of a paper presented at the 108th AWMA Annual Conference and Exhibition (Raleigh, NC 6/22-25/2015).
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| 19. |
- Vechi, Nathalia T., et al.
(författare)
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Ammonia and methane emissions from dairy concentrated animal feeding operations in California, using mobile optical remote sensing
- 2023
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1873-2844 .- 1352-2310. ; 293
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Tidskriftsartikel (refereegranskat)abstract
- Dairy concentrated animal feeding operations (CAFOs) are significant sources of methane (CH4) and ammonia (NH3) emissions in the San Joaquin Valley, California. Optical techniques, namely, remote sensing by Solar Occultation Flux (SOF) and Mobile extractive FTIR (MeFTIR), were used to measure NH3 air column and ground air concentrations of NH3 and CH4, respectively. Campaigns were performed in May and October 2019 and covered 14 dairies located near Bakersfield and Tulare, California. NH3 and CH4 emission rates from single CAFOs averaged 101.9 ± 40.6 kgNH3/h and 437.7 ± 202.0 kgCH4/h, respectively, corresponding to emission factors (EFs) per livestock unit of 9.1 ± 2.7 gNH3/LU/h and 40.1 ± 17.8 gCH4/LU/h. The NH3 emissions had a median standard uncertainty of 17% and an expanded uncertainty (95% Confidence Interval (CI)) of 37%; meanwhile, CH4 emissions estimates had greater uncertainty, median of 25% and 53% (in the 95% CI). Decreasing NH3 to CH4 ratios and NH3 EFs from early afternoon (13:00) to early night (19:00) indicated a diurnal emission pattern with lower ammonia emissions during the night. On average, measured NH3 emissions were 28% higher when compared to daytime emission rates reported in the National Emissions Inventory (NEI) and modeled according to diurnal variation. Measured CH4 emissions were 60% higher than the rates reported in the California Air Resources Board (CARB) inventory. However, comparison with airborne measurements showed similar emission rates. This study demonstrates new air measurement methods, which can be used to quantify emissions over large areas with high spatial resolution and in a relatively short time period. These techniques bridge the gap between satellites and individual CAFOs measurements.
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