scholarly journals Discrete-wavelength DOAS NO<sub>2</sub> slant column retrievals from OMI and TROPOMI

2019 ◽  
Author(s):  
Cristina Ruiz Villena ◽  
Jasdeep S. Anand ◽  
Roland J. Leigh ◽  
Paul S. Monks ◽  
Claire E. Parfitt ◽  
...  
Keyword(s):  
Spatial Information ◽  
Optical Filters ◽  
Point Sources ◽  
Optical Absorption Spectroscopy ◽  
Emission Point ◽  
The World ◽  
Simple Implementation ◽  
Level 2 ◽  
Selection Of ◽  
Good Agreement

Abstract. The use of satellite NO2 data for air quality studies is increasingly revealing the need for observations with higher spatial and temporal resolution. The study of the NO2 diurnal cycle, global sub-urban scale observations, and identification of emission point sources are some examples of important applications not possible at the resolution provided by current instruments. One way to achieve increased spatial resolution is to reduce the spectral information needed for the retrieval, allowing both dimensions of conventional 2-D detectors to be used to record spatial information. In this work we investigate the use of ten discrete wavelengths with the well-established Differential Optical Absorption Spectroscopy (DOAS) technique for NO2 slant column density (SCD) retrievals. To test the concept we use a selection of individual OMI and TROPOMI Level 1B swaths from various regions around the world which contain a mixture of clean and heavily polluted areas. To discretise the data we simulate a set of Gaussian optical filters centred at various key wavelengths of the NO2 absorption cross section. We perform SCD retrievals of the discrete data using a simple implementation of the DOAS algorithm and compare the results with the corresponding Level 2 SCD products, namely QA4ECV for OMI and the operational TROPOMI product. For OMI the overall results from our discrete-wavelength retrieval are in very good agreement with the Level 2 data (mean difference

scholarly journals Discrete-wavelength DOAS NO<sub>2</sub> slant column retrievals from OMI and TROPOMI

2020 ◽  
Vol 13 (4) ◽  
pp. 1735-1756
Author(s):  
Cristina Ruiz Villena ◽  
Jasdeep S. Anand ◽  
Roland J. Leigh ◽  
Paul S. Monks ◽  
Claire E. Parfitt ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
Spatial Information ◽  
Signal To Noise Ratio ◽  
Optical Filters ◽  
Point Sources ◽  
Mean Difference ◽  
Optical Absorption Spectroscopy ◽  
Small Satellites ◽  
Emission Point ◽  
Level 2

Abstract. The use of satellite NO2 data for air quality studies is increasingly revealing the need for observations with higher spatial and temporal resolution. The study of the NO2 diurnal cycle, global sub-urban-scale observations, and identification of emission point sources are some examples of important applications not possible at the resolution provided by current instruments. One way to achieve increased spatial resolution is to reduce the spectral information needed for the retrieval, allowing both dimensions of conventional 2-D detectors to be used to record spatial information. In this work we investigate the use of 10 discrete wavelengths with the well-established differential optical absorption spectroscopy (DOAS) technique for NO2 slant column density (SCD) retrievals. To test the concept we use a selection of individual OMI and TROPOMI Level 1B swaths from various regions around the world, which contain a mixture of clean and heavily polluted areas. To discretise the data we simulate a set of Gaussian optical filters centred at various key wavelengths of the NO2 absorption cross section. We perform SCD retrievals of the discrete data using a simple implementation of the DOAS algorithm and compare the results with the corresponding Level 2 SCD products, namely QA4ECV for OMI and the operational TROPOMI product. For OMI the overall results from our discrete-wavelength retrieval are in very good agreement with the Level 2 data (mean difference <5 %). For TROPOMI the agreement is good (mean difference <11 %), with lower uncertainty owing to its higher signal-to-noise ratio. These discrepancies can be mostly explained by the differences in retrieval implementation. There are some larger differences around the centre of the swath and over water. While further research is needed to address specific retrieval issues, our results indicate that our method has potential. It would allow for simpler, more economic satellite instrument designs for NO2 monitoring at high spatial and temporal resolution. Constellations of small satellites with such instruments on board would be a valuable complement to current and upcoming high-budget hyperspectral instruments.

scholarly journals Estimating the size of a methane emission point-source at different scales: from local to landscape

2016 ◽  
Author(s):  
Stuart N. Riddick ◽  
Sarah Connors ◽  
Andrew D. Robinson ◽  
Alastair J. Manning ◽  
Pippa S. D. Jones ◽  
...  
Keyword(s):  
Point Sources ◽  
Back Trajectories ◽  
Mixing Ratios ◽  
Ch4 Production ◽  
Emission Point ◽  
Landfill Emissions ◽  
Gaussian Plume ◽  
Isotopic Measurements ◽  
Good Agreement ◽  
Modelling Approach

Abstract. High methane (CH4) mixing ratios (up to 4 ppm) have occurred sporadically at our measurement site in Haddenham, Cambridgeshire since July 2012. Isotopic measurements and back trajectories show that the source is the Waterbeach Waste management park 7 km SE of Haddenham. To investigate this further, measurements were made on June 30th and July 1st 2015 at other locations nearer to the source. Landfill emissions have been estimated using three different approaches (WindTrax, Gaussian plume, and NAME InTEM inversion) applied to the measurements made close to source and at Haddenham. The emission estimates derived using the WindTrax and Gaussian plume approaches agree well for the period of intense observations. Applying the Gaussian plume approach to all periods of elevated measurements seen at Haddenham produces year-round and monthly landfill emission estimates. The estimated annual emissions vary between 11.6 and 13.7 Gg CH4 yr−1. The monthly emission estimates are highest in winter (2160 kg hr−1 in February) and lowest in summer (620 kg hr−1 in July). These data identify the effects of environmental conditions on landfill CH4 production and highlight the importance of year-round measurement to capture seasonal variability in CH4 emission. We suggest the landscape inverse modelling approach described in this paper is in good agreement with more labour-intensive near-source approaches and can be used to identify point-sources within an emission landscape to provide high-quality emission estimates.

scholarly journals Observation of slant column NO<sub>2</sub> using the super-zoom mode of AURA-OMI

2011 ◽  
Vol 4 (9) ◽  
pp. 1929-1935 ◽  
Author(s):  
L. C. Valin ◽  
A. R. Russell ◽  
E. J. Bucsela ◽  
J. P. Veefkind ◽  
R. C. Cohen
Keyword(s):  
United Arab Emirates ◽  
Random Noise ◽  
Point Sources ◽  
Optical Absorption Spectroscopy ◽  
Ozone Monitoring Instrument ◽  
Spatial Response ◽  
Individual Detector ◽  
Instrumental Precision ◽  
Good Agreement ◽  
Ground Calibration

Abstract. We retrieve slant column NO2 from the super-zoom mode of the Ozone Monitoring Instrument (OMI) to explore its utility for understanding NOx emissions and variability. Slant column NO2 is operationally retrieved from OMI (Boersma et al., 2007; Bucsela et al., 2006) with a nadir footprint of 13 × 24 km2, the result of averaging eight detector elements on board the instrument. For 85 orbits in late 2004, OMI reported observations from individual "super-zoom" detector elements (spaced at 13 × 3 km2 at nadir). We assess the spatial response of these individual detector elements in-flight and determine an upper-bound on spatial resolution of 9 km, in good agreement with on-ground calibration (7 km FWHM). We determine the precision of the super-zoom mode to be 2.1 × 1015 molecules cm−2, approximately a factor of √8 lower than an identical retrieval at operational scale as expected if random noise dominates the uncertainty. We retrieve slant column NO2 over the Satpura power plant in India; Seoul, South Korea; Dubai, United Arab Emirates; and a set of large point sources on the Rihand Reservoir in India using differential optical absorption spectroscopy (DOAS). Over these sources, the super-zoom mode of OMI observes variation in slant column NO2 of up to 30 × the instrumental precision within one operational footprint.

“To Corrupt a Man in the Midst of a Verse”: Ben Jonson and the Prose of the World

2017 ◽  
Vol 24 (1) ◽  
pp. 46-72
Author(s):  
Jacob Tootalian
Keyword(s):  
Mixed Mode ◽  
Ben Jonson ◽  
Digital Analysis ◽  
Interactive Engagement ◽  
Sentence Level ◽  
Linguistic Patterns ◽  
The World ◽  
Selection Of ◽  
Bartholomew Fair

Ben Jonson's early plays show a marked interest in prose as a counterpoint to the blank verse norm of the Renaissance stage. This essay presents a digital analysis of Jonson's early mixed-mode plays and his two later full-prose comedies. It examines this selection of the Jonsonian corpus using DocuScope, a piece of software that catalogs sentence-level features of texts according to a series of rhetorical categories, highlighting the distinctive linguistic patterns associated with Jonson's verse and prose. Verse tends to employ abstract, morally and emotionally charged language, while prose is more often characterized by expressions that are socially explicit, interrogative, and interactive. In the satirical economy of these plays, Jonson's characters usually adopt verse when they articulate censorious judgements, descending into prose when they wade into the intractable banter of the vicious world. Surprisingly, the prosaic signature that Jonson fashioned in his earlier drama persisted in the two later full-prose comedies. The essay presents readings of Every Man Out of his Humour and Bartholomew Fair, illustrating how the tension between verse and prose that motivated the satirical dynamics of the mixed-mode plays was released in the full-prose comedies. Jonson's final experiments with theatrical prose dramatize the exhaustion of the satirical impulse by submerging his characters almost entirely in the prosaic world of interactive engagement.

Presence, Environment, and Sound and the Role of Imagination

2019 ◽  
pp. 667-681
Author(s):  
Mark Grimshaw-Aagaard
Keyword(s):  
Computer Games ◽  
Virtual World ◽  
Actual World ◽  
Sensory Input ◽  
The World ◽  
Visual Dimension ◽  
The Creation ◽  
First Person Shooter ◽  
Selection Of

Mark Grimshaw-Aagaard addresses the role of sound in the creation of presence in virtual and actual worlds. He argues that imagination is a central part of the generation and selection of perceptual hypotheses—models of the world in which we can act—that emerge from what Grimshaw-Aagaard calls the “exo-environment” (the sensory input) and the “endo-environment” (the cognitive input). Grimshaw-Aagaard further divides the exo-environment into a primarily auditory and a primarily visual dimension and he deals with the actual world of his own apartment and the virtual world of first-person-shooter computer games in order to exemplify how we perceptually construct an environment that allows for the creation of presence.

Collective Decision-making: FIFA from the Perspective of Public Choice

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Florian Follert ◽  
Lukas Richau ◽  
Eike Emrich ◽  
Christian Pierdzioch
Keyword(s):  
Decision Making ◽  
Public Choice ◽  
Choice Theory ◽  
Collective Decision ◽  
Public Confidence ◽  
Collective Decision Making ◽  
Public Choice Theory ◽  
World Cup ◽  
The World ◽  
Selection Of

AbstractVarious scandals have shaken public confidence in football's global governing body, Fédération Internationale de Football Association (FIFA). It is evident that decision-making within such a collective provides incentives for corruption. We apply the Buchanan-Tullock model that is known from Public Choice theory to study collective decision-making within FIFA. On the basis of this theoretical model, we develop specific proposals that can contribute to combating corruption. Three core aspects are discussed: the selection of the World Cup host, transparency in the allocation of budgets, and clear guidelines for FIFA officials and bodies with regard to their rights and accountability. Our insights can contribute to a better understanding of collective decision making in heterogenous groups.

scholarly journals Theoretical and Empirical Characterization of Water as a Factor: Examples and Related Issues with the World Trade Model

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 459
Author(s):  
Ignacio Cazcarro ◽  
Albert E. Steenge
Keyword(s):  
World Trade ◽  
Low Cost ◽  
Virtual Water ◽  
Considerable Change ◽  
Water Research ◽  
Trade Model ◽  
The World ◽  
Main Model ◽  
Selection Of

This article originates from the theoretical and empirical characterization of factors in the World Trade Model (WTM). It first illustrates the usefulness of this type of model for water research to address policy questions related to virtual water trade, water constraints and water scarcity. It also illustrates the importance of certain key decisions regarding the heterogeneity of water and its relation to the technologies being employed and the prices obtained. With regard to WTM, the global economic input–output model in which multiple technologies can produce a “homogeneous output”, it was recently shown that two different mechanisms should be distinguished by which multiple technologies can arise, i.e., from “technology-specific” or from “shared” factors, which implies a mechanism-specific set of prices, quantities and rents. We discuss and extend these characterizations, notably in relation to the real-world characterization of water as a factor (for which we use the terms technology specific, fully shared and “mixed”). We propose that the presence of these separate mechanisms results in the models being sensitive to relatively small variations in specific numerical values. To address this sensitivity, we suggest a specific role for specific (sub)models or key choices to counter unrealistic model outcomes. To support our proposal we present a selection of simulations for aggregated world regions, and show how key results concerning quantities, prices and rents can be subject to considerable change depending on the precise definitions of resource endowments and the technology-specificity of the factors. For instance, depending on the adopted water heterogeneity level, outcomes can vary from relatively low-cost solutions to higher cost ones and can even reach infeasibility. In the main model discussed here (WTM) factor prices are exogenous, which also contributes to the overall numerical sensitivity of the model. All this affects to a large extent our interpretation of the water challenges, which preferably need to be assessed in integrated frameworks, to account for the main socioeconomic variables, technologies and resources.

scholarly journals Tropospheric NO<sub>2</sub> column densities deduced from zenith-sky DOAS measurements in Shanghai, China, and their application to satellite validation

2009 ◽  
Vol 9 (11) ◽  
pp. 3641-3662 ◽  
Author(s):  
D. Chen ◽  
B. Zhou ◽  
S. Beirle ◽  
L. M. Chen ◽  
T. Wagner
Keyword(s):  
Satellite Data ◽  
Urban Site ◽  
Optical Absorption Spectroscopy ◽  
Vertical Column ◽  
Error Sources ◽  
Satellite Validation ◽  
Tropospheric No2 ◽  
Realistic Information ◽  
Good Agreement

Abstract. Zenith-sky scattered sunlight observations using differential optical absorption spectroscopy (DOAS) technique were carried out in Shanghai, China (31.3° N, 121.5° E) since December 2006. At this polluted urban site, the measurements provided NO2 total columns in the daytime. Here, we present a new method to extract time series of tropospheric vertical column densities (VCDs) of NO2 from these observations. The derived tropospheric NO2 VCDs are important quantities for the estimation of emissions and for the validation of satellite observations. Our method makes use of assumptions on the relative NO2 height profiles and the diurnal variation of stratospheric NO2 VCDs. The main error sources arise from the uncertainties in the estimated stratospheric slant column densities (SCDs) and the determination of tropospheric NO2 air mass factor (AMF). For a polluted site like Shanghai, the accuracy of our method is conservatively estimated to be <25% for solar zenith angle (SZA) lower than 70°. From simultaneously performed long-path DOAS measurements, the NO2 surface concentrations at the same site were observed and the corresponding tropospheric NO2 VCDs were estimated using the assumed seasonal NO2 profiles in the planetary boundary layer (PBL). By making a comparison between the tropospheric NO2 VCDs from zenith-sky and long-path DOAS measurements, it is found that the former provides more realistic information about total tropospheric pollution than the latter, so it's more suitable for satellite data validation. A comparison between the tropospheric NO2 VCDs from ground-based zenith-sky measurements and SCIAMACHY was also made. Satellite validation for a strongly polluted area is highly needed, but exhibits also a great challenge. Our comparison shows good agreement, considering in particular the different spatial resolutions between the two measurements. Remaining systematic deviations are most probably related to the uncertainties of satellite data caused by the assumptions on aerosol properties as well as the layer heights of aerosols and NO2.

Patterns of Searching for Information on the World Wide Web: A Pilot Study

2003 ◽  
Vol 92 (3_suppl) ◽  
pp. 1091-1096 ◽  
Author(s):  
Nobuhiko Fujihara ◽  
Asako Miura
Keyword(s):  
World Wide Web ◽  
Undergraduate Students ◽  
Search Engines ◽  
World Wide ◽  
Information Sources ◽  
Task Type ◽  
The Other ◽  
The World ◽  
Selection Of ◽  
Search Domain

The influences of task type on search of the World Wide Web using search engines without limitation of search domain were investigated. 9 graduate and undergraduate students studying psychology (1 woman and 8 men, M age = 25.0 yr., SD = 2.1) participated. Their performance to manipulate the search engines on a closed task with only one answer were compared with their performance on an open task with several possible answers. Analysis showed that the number of actions was larger for the closed task ( M = 91) than for the open task ( M = 46.1). Behaviors such as selection of keywords (averages were 7.9% of all actions for the closed task and 16.7% for the open task) and pressing of the browser's back button (averages were 40.3% of all actions for the closed task and 29.6% for the open task) were also different. On the other hand, behaviors such as selection of hyperlinks, pressing of the home button, and number of browsed pages were similar for both tasks. Search behaviors were influenced by task type when the students searched for information without limitation placed on the information sources.

“Hints to Travellers”, Volume II

Polar Record ◽  
1938 ◽  
Vol 2 (16) ◽  
pp. 131-133
Author(s):  
A.S.
Keyword(s):  
The World ◽  
Selection Of ◽  
General Standard

In the 1938 edition of Hints to Travellers, vol. ii, the editor has produced a handbook on travel rather than a collection of hints, and the general standard is now more comparable with vol. i. The work is the result of the editor's tireless energy and passion for details, combined with a selection of opinions from those who have travelled and explored in most of the relatively unknown parts of the world.

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