scholarly journals N<sub>2</sub>O<sub>5</sub> uptake onto saline mineral dust: a potential missing source of tropospheric ClNO<sub>2</sub> in inland China

2021 ◽  
Author(s):  
Haichao Wang ◽  
Chao Peng ◽  
Xuan Wang ◽  
Shengrong Lou ◽  
Keding Lu ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Transport Model ◽  
Mineral Dust ◽  
Heterogeneous Reaction ◽  
Chemical Transport Model ◽  
Mixing Ratios ◽  
Nitryl Chloride ◽  
Mass Fractions ◽  
The Impact ◽  
Cl Atoms

Abstract. Nitryl chloride (ClNO2), an important precursor of Cl atoms, significantly affects atmospheric oxidation capacity and O3 formation. However, sources of ClNO2 in inland China have not been fully elucidated. In this work, laboratory experiments were conducted to investigate heterogeneous reaction of N2O5 with eight saline mineral dust samples collected from different regions in China, and substantial formation of ClNO2 was observed. ClNO2 yields, φ(ClNO2), showed large variations (ranging from < 0.05 to ~0.77) for different saline mineral dust samples, largely depending on mass fractions of particulate chloride. In addition, for different saline mineral dust samples, φ(ClNO2) could increase, decrease or show insignificant change as RH increased from 18 % to 75 %. We further found that current parameterizations significantly overestimated φ(ClNO2) for heterogeneous uptake of N2O5 onto saline mineral dust. Assuming a uniform φ(ClNO2) value of 0.10 for N2O5 uptake onto mineral dust, we used a 3-D chemical transport model to assess the impact of this reaction on tropospheric ClNO2 in China, and found that weekly mean nighttime maximum ClNO2 mixing ratios could be increased by up to 85 pptv during a severe dust event in May 2017. Overall, our work showed that heterogeneous reaction of N2O5 with saline mineral dust could be an important source of tropospheric ClNO2 in inland China.

scholarly journals Heterogeneous reaction of HO<sub>2</sub> with airborne TiO<sub>2</sub> particles and its implication for climate change mitigation strategies

2017 ◽  
Author(s):  
Daniel R. Moon ◽  
Giorgio S. Taverna ◽  
Clara Anduix-Canto ◽  
Trevor Ingham ◽  
Martyn P. Chipperfield ◽  
...  
Keyword(s):  
Transport Model ◽  
Heterogeneous Reaction ◽  
Three Dimensional ◽  
Mitigation Strategies ◽  
Heterogeneous Reactions ◽  
Chemical Transport Model ◽  
Flow Tube ◽  
Tio2 Particles ◽  
The Impact ◽  
Change Mitigation

Abstract. One geoengineering mitigation strategy for global temperature rises resulting from the increased concentrations of greenhouse gases is to inject particles into the stratosphere to scatter solar radiation back to space, with TiO2 particles emerging as a possible candidate. Uptake coefficients of HO2, γ(HO2), onto sub-micrometre TiO2 particles were measured at room temperature and different relative humidities (RH) using an atmospheric pressure aerosol flow tube coupled to a sensitive HO2 detector. Values of γ(HO2) increased from 0.021 ± 0.001 to 0.036 ± 0.007 as the RH was increased from 11 % to 66 %, and the increase in γ(HO2) correlated with the number of monolayers of water surrounding the TiO2 particles. The impact of the uptake of HO2 onto TiO2 particles on stratospheric concentrations of HO2 and O3 was simulated using the TOMCAT three-dimensional chemical transport model. The model showed that by injecting the amount of TiO2 required to achieve the same cooling effect as the Mt. Pinatubo eruption, heterogeneous reactions between HO2 and TiO2 would have a negligible effect on stratospheric concentrations of HO2 and O3.

scholarly journals The contribution of natural and anthropogenic very short-lived species to stratospheric bromine

2012 ◽  
Vol 12 (1) ◽  
pp. 371-380 ◽  
Author(s):  
R. Hossaini ◽  
M. P. Chipperfield ◽  
W. Feng ◽  
T. J. Breider ◽  
E. Atlas ◽  
...  
Keyword(s):  
Transport Model ◽  
Three Dimensional ◽  
Chemical Transport Model ◽  
Atmospheric Lifetime ◽  
Tropical Tropopause Layer ◽  
Mixing Ratios ◽  
Tropical Tropopause ◽  
Atmospheric Observations ◽  
Surface Mixing ◽  
The Impact

Abstract. We have used a global three-dimensional chemical transport model to quantify the impact of the very short-lived substances (VSLS) CHBr3, CH2Br2, CHBr2Cl, CHBrCl2, CH2BrCl and C2H5-Br on the bromine budget of the stratosphere. Atmospheric observations of these gases allow constraints on surface mixing ratios that, when incorporated into our model, contribute ~4.9–5.2 parts per trillion (ppt) of inorganic bromine (Bry) to the stratosphere. Of this total, ~76 % comes from naturally-emitted CHBr3 and CH2Br2. The remaining species individually contribute modest amounts. However, their accumulated total accounts for up to ~1.2 ppt of the supply and thus should not be ignored. We have compared modelled tropical profiles of a range of VSLS with observations from the recent 2009 NSF HIPPO-1 aircraft campaign. Modelled profiles agree reasonably well with observations from the surface to the lower tropical tropopause layer. We have also considered the poorly studied anthropogenic VSLS, C2H5Br, CH2BrCH2Br, n-C3H7Br and i-C3H7Br. We find the local atmospheric lifetime of these species in the tropical tropopause layer are ~183, 603, 39 and 49 days, respectively. These species, particularly C2H5Br and CH2BrCH2Br, would thus be important carriers of bromine to the stratosphere if emissions were to increase substantially. Our model shows ~70–73 % and ~80–85 % of bromine from these species in the tropical boundary layer can reach the lower stratosphere.

scholarly journals Temperature response measurements from eucalypts give insight into the impact of Australian isoprene emissions on air quality in 2050

2020 ◽  
Vol 20 (10) ◽  
pp. 6193-6206
Author(s):  
Kathryn M. Emmerson ◽  
Malcolm Possell ◽  
Michael J. Aspinwall ◽  
Sebastian Pfautsch ◽  
Mark G. Tjoelker
Keyword(s):  
Air Quality ◽  
Transport Model ◽  
Temperature Response ◽  
Emission Factors ◽  
Eucalyptus Species ◽  
Chemical Transport Model ◽  
Mixing Ratios ◽  
The Impact ◽  
Temperature Responses ◽  
Insight Into

Abstract. Predicting future air quality in Australian cities dominated by eucalypt emissions requires an understanding of their emission potentials in a warmer climate. Here we measure the temperature response in isoprene emissions from saplings of four different Eucalyptus species grown under current and future average summertime temperature conditions. The future conditions represent a 2050 climate under Representative Concentration Pathway 8.5, with average daytime temperatures of 294.5 K. Ramping the temperature from 293 to 328 K resulted in these eucalypts emitting isoprene at temperatures 4–9 K higher than the default maximum emission temperature in the Model of Emissions of Gases and Aerosols from Nature (MEGAN). New basal emission rate measurements were obtained at the standard conditions of 303 K leaf temperature and 1000 µmol m−2 s−1 photosynthetically active radiation and converted into landscape emission factors. We applied the eucalypt temperature responses and emission factors to Australian trees within MEGAN and ran the CSIRO Chemical Transport Model for three summertime campaigns in Australia. Compared to the default model, the new temperature responses resulted in less isoprene emission in the morning and more during hot afternoons, improving the statistical fit of modelled to observed ambient isoprene. Compared to current conditions, an additional 2 ppb of isoprene is predicted in 2050, causing hourly increases up to 21 ppb of ozone and 24-hourly increases of 0.4 µg m−3 of aerosol in Sydney. A 550 ppm CO2 atmosphere in 2050 mitigates these peak Sydney ozone mixing ratios by 4 ppb. Nevertheless, these forecasted increases in ozone are up to one-fifth of the hourly Australian air quality limit, suggesting that anthropogenic NOx should be further reduced to maintain healthy air quality in future.

Assessment of the impact of large changes in the ratio of photolysis rate of nitrate to that of gas nitric acid on HONO concentrations simulated by a 3-D chemical transport model

2021 ◽  
Author(s):  
Yitian Guo ◽  
Junling An ◽  
Jingwei Zhang
Keyword(s):  
Nitric Acid ◽  
Transport Model ◽  
Heterogeneous Reaction ◽  
Ground Surface ◽  
Chemical Transport ◽  
Field Studies ◽  
Chemical Transport Model ◽  
Substantial Impact ◽  
Photolysis Rate ◽  
The Impact

&lt;p&gt;Some studies show that photolysis of nitrate and deposited nitrate and gas nitric acid (HNO&lt;sub&gt;3&lt;/sub&gt;) on the ground surface is much faster than that of HNO&lt;sub&gt;3&lt;/sub&gt;. The former mechanism has been considered as a possible daytime HONO source and discussed in many laboratory and field studies. Although this mechanism is also coupled into some three-dimensional chemical transport models, the effect of large changes in the ratio of photolysis rate of nitrate to that of HNO&lt;sub&gt;3&lt;/sub&gt; (RAT) on HONO concentrations has not been assessed and will be discussed here by using the updated WRF-Chem model. Simulations indicate that in the morning, this mechanism only resulted in a HONO increase of a few ppt, while the heterogeneous reaction of NO&lt;sub&gt;2&lt;/sub&gt; enhanced HONO by about 150 ppt; in the afternoon, however, this mechanism led to a significant HONO increase, with its contribution to HONO concentrations being close to the contribution of the heterogeneous reaction of NO&lt;sub&gt;2&lt;/sub&gt;. In some heavily nitrate-polluted areas, this mechanism contributed more than 80% of HONO concentrations during the afternoon. Large changes in RAT produced a substantial impact on HONO concentrations. When RAT was altered from 15 to 100, increase of HONO concentrations was enhanced by about 6 times. Our results suggest that more laboratory and field studies on the photolysis rates of nitrate and deposited nitrate and HNO&lt;sub&gt;3&lt;/sub&gt; on the ground surface are still needed.&lt;/p&gt;

scholarly journals A revised mineral dust emission scheme in GEOS-Chem: improvements in dust simulations over China

2020 ◽  
Author(s):  
Rong Tian ◽  
Xiaoyan Ma ◽  
Jianqi Zhao
Keyword(s):  
Soil Texture ◽  
Friction Velocity ◽  
Roughness Length ◽  
Transport Model ◽  
Mineral Dust ◽  
Dust Emission ◽  
Northern China ◽  
Spatial And Temporal Variation ◽  
Chemical Transport Model ◽  
The Impact

Abstract. Mineral dust plays a significant role in climate change and air quality, but large uncertainties remain in terms of dust emission prediction. In this study, we improved the treatments of dust emission process in a Global 3-D Chemical Transport model (GEOS-Chem) v12.6.0, by incorporating the geographical variation of aerodynamic roughness length (Z0), smooth roughness length (Z0s), soil texture, introducing Owen effect and Lu and Shao (1999) formulation of sandblasting efficiency α. To investigate the impact of the modifications incorporated in the model, several sensitivity simulations were performed for a severe dust storm during March 27, 2015 to April 2, 2015 over northern China. Results show that simulated threshold friction velocity is very sensitive to the updated Z0 and Z0s field, with the relative difference ranging from 10 % to 60 % compared to the original model with uniform value. An inclusion of Owen effect leads to an increase in surface friction velocity, which mainly occurs in the arid and semi-arid regions of northwest China. The substitution of fixed value of α assumed in original scheme with one varying with friction velocity and soil texture based on observations reduces α by 50 % on average, especially over regions with sand texture. Comparisons of sensitivity simulations and measurements show that the revised scheme with the implement of updates provides more realistic threshold friction velocities and PM10 mass concentrations. The performance of the improved model has been evaluated against surface PM10 observations as well as MODIS aerosol optical depth (AOD) values, showing that the spatial and temporal variation of mineral dust are better captured by the revised scheme. Due to the inclusion of the improvement, average PM10 concentrations at observational sites are more comparable to the observations, and the average mean bias (MB) and normalized mean bias (NMB) values are reduced from −196.29 μg m−3 and −52.79 % to −47.72 μg −3 and −22.46 % respectively. Our study suggests that the erodibility factor, sandblasting efficiency and soil-related properties which are simply assumed in the empirical scheme may lack physical mechanism and spatial-temporal representative. Further study and measurements should be conducted to obtain more realistic and detailed map of these parameters in order to improve dust representation in the model.

scholarly journals Heterogeneous reaction of HO<sub>2</sub> with airborne TiO<sub>2</sub> particles and its implication for climate change mitigation strategies

2018 ◽  
Vol 18 (1) ◽  
pp. 327-338 ◽  
Author(s):  
Daniel R. Moon ◽  
Giorgio S. Taverna ◽  
Clara Anduix-Canto ◽  
Trevor Ingham ◽  
Martyn P. Chipperfield ◽  
...  
Keyword(s):  
Transport Model ◽  
Heterogeneous Reaction ◽  
Three Dimensional ◽  
Mitigation Strategies ◽  
Heterogeneous Reactions ◽  
Chemical Transport Model ◽  
Flow Tube ◽  
Tio2 Particles ◽  
The Impact ◽  
Change Mitigation

Abstract. One geoengineering mitigation strategy for global temperature rises resulting from the increased concentrations of greenhouse gases is to inject particles into the stratosphere to scatter solar radiation back to space, with TiO2 particles emerging as a possible candidate. Uptake coefficients of HO2, γ(HO2), onto sub-micrometre TiO2 particles were measured at room temperature and different relative humidities (RHs) using an atmospheric pressure aerosol flow tube coupled to a sensitive HO2 detector. Values of γ(HO2) increased from 0.021 ± 0.001 to 0.036 ± 0.007 as the RH was increased from 11 to 66 %, and the increase in γ(HO2) correlated with the number of monolayers of water surrounding the TiO2 particles. The impact of the uptake of HO2 onto TiO2 particles on stratospheric concentrations of HO2 and O3 was simulated using the TOMCAT three-dimensional chemical transport model. The model showed that, when injecting the amount of TiO2 required to achieve the same cooling effect as the Mt Pinatubo eruption, heterogeneous reactions between HO2 and TiO2 would have a negligible effect on stratospheric concentrations of HO2 and O3.

scholarly journals A revised mineral dust emission scheme in GEOS-Chem: improvements in dust simulations over China

2021 ◽  
Vol 21 (6) ◽  
pp. 4319-4337
Author(s):  
Rong Tian ◽  
Xiaoyan Ma ◽  
Jianqi Zhao
Keyword(s):  
Soil Texture ◽  
Friction Velocity ◽  
Roughness Length ◽  
Transport Model ◽  
Mineral Dust ◽  
Dust Emission ◽  
Northern China ◽  
Spatial And Temporal Variation ◽  
Chemical Transport Model ◽  
The Impact

Abstract. Mineral dust plays a significant role in climate change and air quality, but large uncertainties remain in terms of dust emission prediction. In this study, we improved treatment of the dust emission process in a global 3-D chemical transport model (GEOS-Chem v12.6.0), by incorporating the geographical variation of aerodynamic roughness length (Z0), smooth roughness length (Z0s) and soil texture and by introducing the Owen effect and the formulation of the sandblasting efficiency α by Lu and Shao (1999). To investigate the impact of the modifications incorporated in the model, several sensitivity simulations were performed for a severe dust storm during 27 March to 2 April 2015 over northern China. Results show that simulated threshold friction velocity is very sensitive to the updated Z0 and Z0s field, with the relative difference ranging from 10 % to 60 % compared to the original model with a uniform value. The inclusion of the Owen effect leads to an increase in surface friction velocity, which mainly occurs in the arid and semi-arid regions of northwest China. The substitution of a fixed value of α assumed in the original scheme with one varying with friction velocity and soil texture based on observations reduces α by 50 % on average, especially over regions with sand texture. Comparisons of sensitivity simulations and measurements show that the revised scheme with the implementation of updates provides more realistic threshold friction velocities and PM10 mass concentrations. The performance of the improved model has been evaluated against surface PM10 observations as well as MODIS aerosol optical depth (AOD) values, showing that the spatial and temporal variation of mineral dust are better captured by the revised scheme. Due to the inclusion of the improvement, average PM10 concentrations at observational sites are more comparable to the observations, and the average mean bias (MB) and normalized mean bias (NMB) values are reduced from −196.29 µg m−3 and −52.79 % to −47.72 µg m−3 and −22.46 % respectively. Our study suggests that the erodibility factor, sandblasting efficiency and soil-related properties which are simply assumed in the empirical scheme may lack a physical mechanism and spatial–temporal representativeness. Further study and measurements should be conducted to obtain a more realistic and detailed map of these parameters in order to improve dust representation in the model.

scholarly journals Impact of deep convection and dehydration on bromine loading in the upper troposphere and lower stratosphere

2011 ◽  
Vol 11 (1) ◽  
pp. 121-162 ◽  
Author(s):  
J. Aschmann ◽  
B.-M. Sinnhuber ◽  
M. P. Chipperfield ◽  
R. Hossaini
Keyword(s):  
Lower Stratosphere ◽  
Transport Model ◽  
Deep Convection ◽  
Three Dimensional ◽  
Convective Activity ◽  
Chemical Transport Model ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Entire Amount ◽  
The Impact

Abstract. Stratospheric bromine loading due to very short-lived substances is investigated with a three-dimensional chemical transport model over a period of 21 years using meteorological input data from the European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis from 1989 to the end of 2009. Within this framework we analyze the impact of dehydration and deep convection on the amount of stratospheric bromine using an idealized and a detailed full chemistry approach. We model the two most important brominated short-lived substances, bromoform (CHBr3) and dibromomethane (CH2Br2), assuming a uniform detrainment mixing ratio of 1 part per trillion by volume (pptv) for both species. The contribution of very short-lived substances to stratospheric bromine varies drastically with the applied dehydration mechanism and the associated scavenging of soluble species ranging from 3.4 pptv in the idealized setup up to 5 pptv using the full chemistry scheme. In the latter case virtually the entire amount of bromine originating from very short-lived source gases is able to reach the stratosphere thus rendering the impact of dehydration and scavenging on inorganic bromine in the tropopause insignificant. Furthermore, our long-term calculations show that the mixing ratios of very short-lived substances are strongly correlated to convective activity, i.e. intensified convection leads to higher amounts of very short-lived substances in the upper troposphere/lower stratosphere especially under extreme conditions like El Niño seasons. However, this does not apply to the inorganic brominated product gases whose concentrations are anti-correlated to convective activity mainly due to convective dilution and possible scavenging, depending on the applied approach.

scholarly journals Impact of deep convection and dehydration on bromine loading in the upper troposphere and lower stratosphere

2011 ◽  
Vol 11 (6) ◽  
pp. 2671-2687 ◽  
Author(s):  
J. Aschmann ◽  
B.-M. Sinnhuber ◽  
M. P. Chipperfield ◽  
R. Hossaini
Keyword(s):  
Lower Stratosphere ◽  
Transport Model ◽  
Deep Convection ◽  
Three Dimensional ◽  
Convective Activity ◽  
Chemical Transport Model ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Entire Amount ◽  
The Impact

Abstract. Stratospheric bromine loading due to very short-lived substances is investigated with a three-dimensional chemical transport model over a period of 21 years using meteorological input data from the European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis from 1989 to the end of 2009. Within this framework we analyze the impact of dehydration and deep convection on the amount of stratospheric bromine using an idealized and a detailed full chemistry approach. We model the two most important brominated short-lived substances, bromoform (CHBr3) and dibromomethane (CH2Br2), assuming a uniform convective detrainment mixing ratio of 1 part per trillion by volume (pptv) for both species. The contribution of very short-lived substances to stratospheric bromine varies drastically with the applied dehydration mechanism and the associated scavenging of soluble species ranging from 3.4 pptv in the idealized setup up to 5 pptv using the full chemistry scheme. In the latter case virtually the entire amount of bromine originating from very short-lived source gases is able to reach the stratosphere thus rendering the impact of dehydration and scavenging on inorganic bromine in the tropopause insignificant. Furthermore, our long-term calculations show that the mixing ratios of very short-lived substances are strongly correlated to convective activity, i.e. intensified convection leads to higher amounts of very short-lived substances in the upper troposphere/lower stratosphere especially under extreme conditions like El Niño seasons. However, this does not apply to the inorganic brominated product gases whose concentrations are anti-correlated to convective activity mainly due to convective dilution and possible scavenging, depending on the applied approach.

A revised mineral dust emission scheme in GEOS-Chem: improvements in dust simulations over China

2021 ◽  
Author(s):  
Rong Tian ◽  
Xiaoyan Ma ◽  
Jianqi Zhao
Keyword(s):  
Soil Texture ◽  
Friction Velocity ◽  
Roughness Length ◽  
Transport Model ◽  
Mineral Dust ◽  
Dust Emission ◽  
Northern China ◽  
Spatial And Temporal Variation ◽  
Chemical Transport Model ◽  
The Impact

&lt;p&gt;Mineral dust plays a significant role in climate change and air quality, but large uncertainties remain in terms of dust emission prediction. In this study, we improved the treatments of dust emission process in a Global 3-D Chemical Transport model (GEOS-Chem) v12.6.0, by incorporating the geographical variation of aerodynamic roughness length (Z&lt;sub&gt;0&lt;/sub&gt;), smooth roughness length (Z&lt;sub&gt;0s&lt;/sub&gt;), soil texture, introducing Owen effect and Lu and Shao (1999) formulation of sandblasting efficiency &amp;#945;. To investigate the impact of the modifications incorporated in the model, several sensitivity simulations were performed for a severe dust storm during March 27, 2015 to April 2, 2015 over northern China. Results show that simulated threshold friction velocity is very sensitive to the updated Z&lt;sub&gt;0&lt;/sub&gt; and Z&lt;sub&gt;0s&lt;/sub&gt; field, with the relative difference ranging from 10% to 60% compared to the original model with uniform value. An inclusion of Owen effect leads to an increase in surface friction velocity, which mainly occurs in the arid and semi-arid regions of northwest China. The substitution of fixed value of &amp;#945; assumed in original scheme with one varying with friction velocity and soil texture based on observations reduces &amp;#945; by 50% on average, especially over regions with sand texture. Comparisons of sensitivity simulations and measurements show that the revised scheme with the implement of updates provides more realistic threshold friction velocities and PM&lt;sub&gt;10&lt;/sub&gt; mass concentrations. The performance of the improved model has been evaluated against surface PM&lt;sub&gt;10&lt;/sub&gt; observations as well as MODIS aerosol optical depth (AOD) values, showing that the spatial and temporal variation of mineral dust are better captured by the revised scheme. Due to the inclusion of the improvement, average PM&lt;sub&gt;10 &lt;/sub&gt;concentrations at observational sites are more comparable to the observations, and the average mean bias (MB) and normalized mean bias (NMB) values are reduced from -196.29&amp;#956;g m&lt;sup&gt;-3 &lt;/sup&gt;and -52.79% to -47.72&amp;#956;g m&lt;sup&gt;-3&lt;/sup&gt; and -22.46% respectively. Our study suggests that the erodibility factor, sandblasting efficiency and soil-related properties which are simply assumed in the empirical scheme may lack physical mechanism and spatial-temporal representative. Further study and measurements should be conducted to obtain more realistic and detailed map of these parameters in order to improve dust representation in the model.&amp;#160;&lt;/p&gt;

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