scholarly journals Stratospheric O<sub>3</sub> changes during 2001–2010: the small role of solar flux variations in a CTM

2013 ◽  
Vol 13 (5) ◽  
pp. 12263-12286
Author(s):  
S. S. Dhomse ◽  
M. P. Chipperfield ◽  
W. Feng ◽  
W. T. Ball ◽  
Y. C. Unruh ◽  
...  
Keyword(s):  
Transport Model ◽  
Solar Flux ◽  
Chemical Transport Model ◽  
Weather Forecasts ◽  
Broadband Emission ◽  
Short Time Span ◽  
Stratospheric Dynamics ◽  
Modelling Studies ◽  
Short Time

Abstract. Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Experiment (SORCE) show different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL-SSI, SATIRE-S). Some modelling studies have suggested that stratospheric/lower mesospheric O3 changes during solar cycle 23 (1996–2008) can only be reproduced if SORCE solar fluxes are used. We have used a 3-D chemical transport model (CTM), forced by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), to simulate middle atmospheric O3 using three different solar flux datasets (SORCE, NRL-SSI and SATIRE-S). Simulated O3 changes are compared with Microwave Limb Sounder (MLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. Modelled O3 anomalies from all solar flux datasets show good agreement with the observations, despite the different flux variations. The off-line CTM reproduces these changes through dynamical information contained in the analyses. A notable feature during this period is a robust positive solar signal in the tropical middle stratosphere due to changes in stratospheric dynamics. Ozone changes in the lower mesosphere cannot be used to discriminate between solar flux datasets due to large uncertainties and the short time span of the observations. Overall this study suggests that, in a CTM, the UV variations detected by SORCE are not necessary to reproduce observed stratospheric O3 changes during 2001–2010.

scholarly journals Stratospheric O3 changes during 2001–2010: the small role of solar flux variations in a chemical transport model

2013 ◽  
Vol 13 (19) ◽  
pp. 10113-10123 ◽  
Author(s):  
S. S. Dhomse ◽  
M. P. Chipperfield ◽  
W. Feng ◽  
W. T. Ball ◽  
Y. C. Unruh ◽  
...  
Keyword(s):  
Transport Model ◽  
Chemical Transport ◽  
Solar Flux ◽  
Data Sets ◽  
Chemical Transport Model ◽  
Weather Forecasts ◽  
Flux Data ◽  
Broadband Emission ◽  
Short Time Span ◽  
Modelling Studies

Abstract. Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Experiment (SORCE) show different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL-SSI, SATIRE-S). Some modelling studies have suggested that stratospheric/lower mesospheric O3 changes during solar cycle 23 (1996–2008) can only be reproduced if SORCE solar fluxes are used. We have used a 3-D chemical transport model (CTM), forced by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), to simulate middle atmospheric O3 using three different solar flux data sets (SORCE, NRL-SSI and SATIRE-S). Simulated O3 changes are compared with Microwave Limb Sounder (MLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. Modelled O3 anomalies from all solar flux data sets show good agreement with the observations, despite the different flux variations. The off-line CTM reproduces these changes through dynamical information contained in the analyses. A notable feature during this period is a robust positive solar signal in the tropical middle stratosphere, which is due to realistic dynamical changes in our simulations. Ozone changes in the lower mesosphere cannot be used to discriminate between solar flux data sets due to large uncertainties and the short time span of the observations. Overall this study suggests that, in a CTM, the UV variations detected by SORCE are not necessary to reproduce observed stratospheric O3 changes during 2001–2010.

scholarly journals A new diagnostic for tropospheric ozone production

2017 ◽  
Author(s):  
Peter M. Edwards ◽  
Mathew J. Evans
Keyword(s):  
Air Quality ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Chemical Transport ◽  
Ozone Production ◽  
Chemical Transport Model ◽  
Organic Species ◽  
Earth’S Climate ◽  
Oxidation Of Organics

Abstract. Tropospheric ozone is important for the Earth’s climate and air quality. It is produced during the oxidation of organics in the presence of nitrogen oxides. Due to the range of organic species emitted and the chain like nature of their oxidation, this chemistry is complex and understanding the role of different processes (emission, deposition, chemistry) is difficult. We demonstrate a new methodology for diagnosing ozone production based on the processing of bonds contained within emitted molecules, the fate of which is determined by the conservation of spin of the bonding electrons. Using this methodology to diagnose ozone production in the GEOS-Chem chemical transport model, we demonstrate its advantages over the standard diagnostic. We show that the number of bonds emitted, their chemistry and lifetime, and feedbacks on OH are all important in determining the ozone production within the model and its sensitivity to changes. This insight may allow future model-model comparisons to better identify the root causes of model differences.

scholarly journals Sulfate-nitrate-ammonium aerosols over China: response to 2000–2015 emission changes of sulfur dioxide, nitrogen oxides, and ammonia

2013 ◽  
Vol 13 (5) ◽  
pp. 2635-2652 ◽  
Author(s):  
Y. Wang ◽  
Q. Q. Zhang ◽  
K. He ◽  
Q. Zhang ◽  
L. Chai
Keyword(s):  
Emission Reduction ◽  
Transport Model ◽  
Critical Role ◽  
Sufficient Information ◽  
Nox Emissions ◽  
Chemical Transport Model ◽  
Dominant Component ◽  
Emission Changes ◽  
Emission Reduction Target

Abstract. We use a chemical transport model to examine the change of sulfate-nitrate-ammonium (SNA) aerosols over China due to anthropogenic emission changes of their precursors (SO2, NOx and NH3) from 2000 to 2015. From 2000 to 2006, annual mean SNA concentrations increased by about 60% over China as a result of the 60% and 80% increases in SO2 and NOx emissions. During this period, sulfate is the dominant component of SNA over South China (SC) and Sichuan Basin (SCB), while nitrate and sulfate contribute equally over North China (NC). Based on emission reduction targets in the 12th (2011–2015) Five-Year Plan (FYP), China's total SO2 and NOx emissions are projected to change by −16% and +16% from 2006 to 2015, respectively. The amount of NH3 emissions in 2015 is uncertain, given the lack of sufficient information on the past and present levels of NH3 emissions in China. With no change in NH3 emissions, SNA mass concentrations in 2015 will decrease over SCB and SC compared to their 2006 levels, but increase over NC where the magnitude of nitrate increase exceeds that of sulfate reduction. This suggests that the SO2 emission reduction target set by the 12th FYP, although effective in reducing SNA over SC and SCB, will not be successful over NC, for which NOx emission control needs to be strengthened. If NH3 emissions are allowed to keep their recent growth rate and increase by +16% from 2006 to 2015, the benefit of SO2 reduction will be completely offset over all of China due to the significant increase of nitrate, demonstrating the critical role of NH3 in regulating nitrate. The effective strategy to control SNA and hence PM2.5 pollution over China should thus be based on improving understanding of current NH3 emissions and putting more emphasis on controlling NH3 emissions in the future.

The Role of Transnational Companies in the Brazilian Defence Tripod

1991 ◽  
Vol 23 (3) ◽  
pp. 573-597 ◽  
Author(s):  
Raul De Gouvea Neto
Keyword(s):  
Rapid Development ◽  
Vital Role ◽  
Political Support ◽  
Brazilian Government ◽  
Defence Industry ◽  
Short Time Span ◽  
Transnational Companies ◽  
Industrialised Countries ◽  
Short Time

Within a short time span Brazil became one of the world's largest producers of defence hardware. In 1987, Brazil was the fifth largest exporter of arms worldwide and the second largest arms producer among the newly industrialised countries (NICs). This article argues that the roots of this rapid development of the Brazilian Defence Industry (BDI) lie in the vital role of multinational companies (MNCs) and in the harmonious tripod orchestrated by the Brazilian government. The State, through its interaction with the Brazilian private sector and with subsidiaries of MNCs, brought together the political support, a supply of funds, the manufacturing capability and technology that are vital in any attempt to establish an indigenous defence industry. Above all, the Brazilian government achieved the balanced coordination of these variables essential for maintaining the dynamics of the industry.

scholarly journals Long-term observational constraints of organic aerosol dependence on inorganic species in the southeast US

2020 ◽  
Author(s):  
Yiqi Zheng ◽  
Joel A. Thornton ◽  
Nga Lee Ng ◽  
Hansen Cao ◽  
Daven K. Henze ◽  
...  
Keyword(s):  
Air Quality ◽  
Transport Model ◽  
Organic Aerosol ◽  
Chemical Transport Model ◽  
Anthropogenic Pollutants ◽  
Aerosol Acidity ◽  
Inorganic Species ◽  
Southeast Us

Abstract. Organic aerosol (OA), with a large biogenic fraction in summertime southeast US, adversely impacts on air quality and human health. Stringent air quality controls have recently reduced anthropogenic pollutants including sulfate, whose impact on OA remains unclear. Three filter measurement networks provide long-term constraints on the sensitivity of OA to changes in inorganic species, including sulfate and ammonia. The 2000–2013 summertime OA decreases by 1.7~1.9 %/year with little month-to-month variability, while sulfate declines rapidly with significant monthly difference in early 2000s. In contrast, modeled OA from a chemical-transport model (GEOS-Chem) decreases by 4.9 %/year with much larger month-to-month variability, largely due to the predominant role of acid-catalyzed reactive uptake of epoxydiols (IEPOX) onto sulfate. The overestimated modeled OA dependence on sulfate can be improved by implementing a coating effect and assuming constant aerosol acidity, suggesting the needs to revisit IEPOX reactive uptake in current models. Our work highlights the importance of secondary OA formation pathways that are weakly dependent on inorganic aerosol in a region that is heavily influenced by both biogenic and anthropogenic emissions.

scholarly journals Satellite observations of stratospheric hydrogen fluoride and comparisons with SLIMCAT calculations

2015 ◽  
Vol 15 (23) ◽  
pp. 34361-34405 ◽  
Author(s):  
J. J. Harrison ◽  
M. P. Chipperfield ◽  
C. D. Boone ◽  
S. S. Dhomse ◽  
P. F. Bernath ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Montreal Protocol ◽  
Chemical Transport Model ◽  
Slowing Down ◽  
Rate Of Increase ◽  
Stratospheric Dynamics ◽  
Chemistry Experiment

Abstract. The vast majority of emissions of fluorine-containing molecules are anthropogenic in nature, e.g. chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Many of these fluorine-containing species deplete stratospheric ozone, and are regulated by the Montreal Protocol. Once in the atmosphere they slowly degrade, ultimately leading to the formation of HF, the dominant reservoir of stratospheric fluorine due to its extreme stability. Monitoring the growth of stratospheric HF is therefore an important marker for the success of the Montreal Protocol. We report the comparison of global distributions and trends of HF measured in the Earth's atmosphere by the satellite remote-sensing instruments ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer), which has been recording atmospheric spectra since 2004, and HALOE (HALogen Occultation Experiment), which recorded atmospheric spectra between 1991 and 2005, with the output of SLIMCAT, a state-of-the-art three-dimensional chemical transport model. In general the agreement between observation and model is good, although the ACE-FTS measurements are biased high by ∼ 10 % relative to HALOE. The observed global HF trends reveal a substantial slowing down in the rate of increase of HF since the 1990s: 4.97 ± 0.12 % year-1 (1991–1997; HALOE), 1.12 ± 0.08 % year-1 (1998–2005; HALOE), and 0.52 ± 0.03 % year-1 (2004–2012; ACE-FTS). In comparison, SLIMCAT calculates trends of 4.01, 1.10, and 0.48 % year-1, respectively, for the same periods; the agreement is very good for all but the earlier of the two HALOE periods. Furthermore, the observations reveal variations in the HF trends with latitude and altitude, for example between 2004 and 2012 HF actually decreased in the Southern Hemisphere below ∼ 35 km. SLIMCAT calculations broadly agree with these observations, most notably between 2004 and 2012. Such variations are attributed to variability in stratospheric dynamics over the observation period.

scholarly journals Satellite observations of stratospheric carbonyl fluoride

2014 ◽  
Vol 14 (12) ◽  
pp. 18127-18180 ◽  
Author(s):  
J. J. Harrison ◽  
M. P. Chipperfield ◽  
A. Dudhia ◽  
S. Cai ◽  
S. Dhomse ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Thermal Emission ◽  
Transport Model ◽  
Michelson Interferometer ◽  
Three Dimensional ◽  
Chemical Transport Model ◽  
Northern Latitudes ◽  
Stratospheric Dynamics ◽  
The Tropics ◽  
Carbonyl Fluoride

Abstract. The vast majority of emissions of fluorine-containing molecules are anthropogenic in nature, e.g. chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). These molecules slowly degrade in the atmosphere leading to the formation of HF, COF2, and COClF, which are the main fluorine-containing species in the stratosphere. Ultimately both COF2 and COClF further degrade to form HF, an almost permanent reservoir of stratospheric fluorine due to its extreme stability. Carbonyl fluoride (COF2) is the second most abundant stratospheric "inorganic" fluorine reservoir with main sources being the atmospheric degradation of CFC-12 (CCl2F2), HCFC-22 (CHF2Cl), and CFC-113 (CF2ClCFCl2). This work reports the first global distributions of carbonyl fluoride in the Earth's atmosphere using infrared satellite remote-sensing measurements by the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS), which has been recording atmospheric spectra since 2004, and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument, which has recorded thermal emission atmospheric spectra between 2002 and 2012. The observations reveal a high degree of seasonal and latitudinal variability over the course of a year. These have been compared with the output of SLIMCAT, a state-of-the-art three-dimensional chemical transport model. In general the observations agree well with each other and compare well with SLIMCAT, although MIPAS is biased high by as much as ~30%. Between January 2004 and September 2010 COF2 grew most rapidly at altitudes above ~25 km in the southern latitudes and at altitudes below ~25 km in the northern latitudes, whereas it declined most rapidly in the tropics. These variations are attributed to changes in stratospheric dynamics over the observation period. The overall COF2 global trend over this period is calculated as 0.85 ± 0.34 % year−1 (MIPAS), 0.30 ± 0.44% year−1 (ACE), and 0.88% year−1 (SLIMCAT).

Street name changes as language and identity inscription in the cityscape

2021 ◽  
Vol 7 (s5) ◽  
Author(s):  
Peter K. W. Tan ◽  
Christoph Purschke
Keyword(s):  
National Identity ◽  
Language Policy ◽  
Time Span ◽  
City Centre ◽  
Kuala Lumpur ◽  
Short Time Span ◽  
Language Selection ◽  
Map Data ◽  
Short Time

Abstract This article examines the role of language selection in constructing the cityscape of highly multilingual, postcolonial places like Malaysia and Namibia. The relationship between language policy, the construction of a national identity as well as linguistic inscriptions in the cityscape can be seen as part of language planning in relation to what gets represented, by whom, and for what purpose. We focus on street names as a typical target of language policy. In postcolonial societies, these renegotiations of the cityscape can be analysed against the backdrop of different processes, such as the erasure of names commemorating the colonial past, the inscription of important figures of the newly established nations, or the curation of the language regime with respect to the presence and symbolical function of languages. Using contrastive data and methodology, we analyse the renegotiation of postcolonial cityscapes in Kuala Lumpur (historical city centre, map data, large time span) and Windhoek (entire cityscape, newspaper reports, short time span). Our analysis establishes a notion of how the cityscape as a complex sociosymbolic text is being constantly rewritten by its actors. We find different motives attached to such processes of cultural representation, including national identity building and ideological consolidation of the cityscape.

scholarly journals Bromoform and dibromomethane in the tropics: a 3-D model study of chemistry and transport

2010 ◽  
Vol 10 (2) ◽  
pp. 719-735 ◽  
Author(s):  
R. Hossaini ◽  
M. P. Chipperfield ◽  
B. M. Monge-Sanz ◽  
N. A. D. Richards ◽  
E. Atlas ◽  
...  
Keyword(s):  
Transport Model ◽  
Three Dimensional ◽  
Vertical Motion ◽  
Chemical Transport Model ◽  
Heating Rates ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Modelling Studies ◽  
Vertical Winds ◽  
The Tropics

Abstract. We have developed a detailed chemical scheme for the degradation of the short-lived source gases bromoform (CHBr3) and dibromomethane (CH2Br2) and implemented it in the TOMCAT/SLIMCAT three-dimensional (3-D) chemical transport model (CTM). The CTM has been used to predict the distribution of the two source gases (SGs) and 11 of their organic product gases (PGs). These first global calculations of the organic PGs show that their abundance is small. The longest lived organic PGs are CBr2O and CHBrO, but their peak tropospheric abundance relative to the surface volume mixing ratio (vmr) of the SGs is less than 5%. We calculate their mean local tropospheric lifetimes in the tropics to be ~7 and ~2 days (due to photolysis), respectively. Therefore, the assumption in previous modelling studies that SG degradation leads immediately to inorganic bromine seems reasonable. We have compared observed tropical SG profiles from a number of aircraft campaigns with various model experiments. In the tropical tropopause layer (TTL) we find that the CTM run using p levels (TOMCAT) and vertical winds from analysed divergence overestimates the abundance of CH2Br2, and to a lesser extent CHBr3, although the data is sparse and comparisons are not conclusive. Better agreement in the TTL is obtained in the sensitivity run using θ levels (SLIMCAT) and vertical motion from diabatic heating rates. Trajectory estimates of residence times in the two model versions show slower vertical transport in the SLIMCAT θ-level version. In the p-level model even when we switch off convection we still find significant amounts of the SGs considered may reach the cold point tropopause; the stratospheric source gas injection (SGI) is only reduced by ~16% for CHBr3 and ~2% for CH2Br2 without convection. Overall, the relative importance of the SG pathway and the PG pathway for transport of bromine to the stratospheric overworld (θ>380 K) has been assessed. Assuming a 10-day washout lifetime of Bry in TOMCAT, we find the delivery of total Br from CHBr3 to be 0.72 pptv with ~53% of this coming from SGI. Similary, for CH2Br2 we find a total Br value of 1.69 pptv with ~94% coming from SGI. We infer that these species contribute ~2.4 pptv of inorganic bromine to the lower stratosphere with SGI being the dominant pathway. Slower transport to and through the TTL would decrease this estimate.

scholarly journals A new diagnostic for tropospheric ozone production

2017 ◽  
Vol 17 (22) ◽  
pp. 13669-13680 ◽  
Author(s):  
Peter M. Edwards ◽  
Mathew J. Evans
Keyword(s):  
Air Quality ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Chemical Transport ◽  
Ozone Production ◽  
Chemical Transport Model ◽  
Organic Species ◽  
Earth’S Climate ◽  
Oxidation Of Organics

Abstract. Tropospheric ozone is important for the Earth's climate and air quality. It is produced during the oxidation of organics in the presence of nitrogen oxides. Due to the range of organic species emitted and the chain-like nature of their oxidation, this chemistry is complex and understanding the role of different processes (emission, deposition, chemistry) is difficult. We demonstrate a new methodology for diagnosing ozone production based on the processing of bonds contained within emitted molecules, the fate of which is determined by the conservation of spin of the bonding electrons. Using this methodology to diagnose ozone production in the GEOS-Chem chemical transport model, we demonstrate its advantages over the standard diagnostic. We show that the number of bonds emitted, their chemistry and lifetime, and feedbacks on OH are all important in determining the ozone production within the model and its sensitivity to changes. This insight may allow future model–model comparisons to better identify the root causes of model differences.

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