Observed Ozone Concentrations Research Articles

THE COMPARISON OF OXIDATION EFFICIENCY OF REACTIVE OXYGEN SPECIES (ROS): PILOT SCALE OF MICROBUBBLE TECHNOLOGIES WITH OXYGEN CONCENTRATION

The objective of this study is to assess and compare the effectiveness of an oxidizing agent. Within the field of advanced oxidation processes (AOPs), ozone, a highly reactive gas, generates reactive oxygen species (ROS) as byproducts through chemical reactions. The study employed a dielectric barrier discharge (DBD) plasma generator to produce ozone gas. This study was carried out under different gas source conditions, including both air and oxygen. Additionally, the ROS produced as byproducts from the interaction between ozone gas and water were measured using oxidation-reduction potential (ORP) values. The ORP values exhibit strong foundational attributes for both ozone dissolution and ROS oxidation efficiency. To extend the interaction duration between ozone gas and water, a stone diffuser was utilized to introduce ozone gas into the water. This mechanism resulted in the creation of ozone microbubbles through a process known as cavitation. The results illustrate a positive relationship between the flow rate and ozone yield. This trend reached its highpoint with the highest observed ozone concentrations approximately 14.11 mg/L for oxygen and 4.55 mg/L for air both achieved at a flow rate of 11 L/min. Furthermore, the highest ozone concentrations were recorded at 15.17 mg/L for oxygen and 12.59 mg/L for air after a 10 min discharge period. Interestingly, ozone generated from oxygen feed gas exhibited a higher concentration yield than that from air feed gas. Moreover, the ORP value displayed a continuous increase with longer treatment times, eventually stabilizing at around the 15 min. This pattern corresponded to the water reaching its highest the ORP values approximately 821 mV for oxygen and 569 mV for air. In summary, this study emphasizes the potential benefits of utilizing ozone as an effective oxidant in both gaseous (ozone gas) and liquid (ROS) phases. It especially emphasizes the essential role played by the generation of ozone and ROS from an oxygen-fed gas source. Moreover, it highlights the significance of maintaining an optimal flow rate of 11 L/min and a discharge duration of 10 min for achieving the highest ozone concentration. Similarly, a treatment time of 15 min for the liquid phase is recommended to maximize ORP values. Both of these values indicate the highest potential advantages for producing an effective oxidant.

Effectiveness of emission controls implemented since 2000 on ambient ozone concentrations in multiple timescales in Japan: An emission inventory development and simulation study

It has been reported that ambient ozone concentrations in Japan have not been effectively suppressed by precursor emission controls. In this study, we developed an unprecedented long-term emission inventory of ozone precursors, including nitrogen oxide (NOX) and volatile organic compounds (VOCs), in Japan. The developed emission inventory, which explicitly represents changes in emissions caused by emission controls and variation in activities from 2000 to 2019, revealed that emission controls implemented for vehicles, large point sources, and fugitive VOC sources effectively reduced precursor emissions. The impact of emission changes on ozone concentrations at six different timescales was evaluated using air quality simulations. Three of them corresponded to annual mean values of daily ozone concentrations, and the others corresponded to annual high ozone concentrations. The simulations performed better at higher ozone concentrations. The simulation results suggested that emission controls have helped suppress annual high ozone concentrations, whereas the annual mean values of daily ozone concentrations may have increased in populated urban areas because reduced NOX emissions weakened the titration of ozone. Overall changes in the simulated ozone concentrations over different timescales were generally consistent with those in the observed ozone concentrations. These findings highlight the importance of evaluating the impact of emission controls on ozone concentrations over multiple timescales. The differences in the sensitivities of ozone concentrations to emission controls were clearly explained by the ozone sensitivity regimes implied by the ratios of formaldehyde to nitrogen dioxide. The outcomes of this study could assist countries beyond Japan in developing effective strategies to manage ozone pollution.

Development of an automated pump-efficiency measuring system for ozonesondes utilizing an airbag-type flowmeter

Abstract. We report here on a system developed to automatically measure the flow rate characteristics (i.e., the pump efficiency) of pumps on ozonesondes under various pressure levels simulating upper-air conditions. The system consists of a flow measurement unit incorporating a polyethylene airbag, a pressure control unit that reproduces low-pressure environmental conditions, and a control unit that integrates and controls these elements to enable fully automatic measurement. The Japan Meteorological Agency (JMA) has operationally measured pump efficiency for electrochemical concentration cell (ECC) ozonesondes using the system since 2009, resulting in a significant amount of related data. Extensive measurements collected for the same ozonesonde pump over a period of around 12 years indicate the long-term stability of the system's performance. These long-term data also show that ozonesonde pump flow characteristics differed among production lots. Evaluation of the impacts of variance in these characteristics on observed ozone concentration data indicated that the influence on total ozone estimation was up to approximately 4 %, the standard deviation per lot was approximately 1 %, and the standard deviation among lots was approximately 0.6 %.

An explicit study of local ozone budget and NOx-VOCs sensitivity in Shenzhen China

In China, a significant reduction in primary pollution has been observed due to the Clean Air Action since 2013, and ozone pollution has become increasingly prominent over the past years. Pearl River Delta (PRD) is one of the most successful regions concerning primary pollution control, while is suffering from severe ozone pollution during autumn. In this study, we present a field campaign in Shenzhen, a megacity in PRD, in October 2018 with measurements of ozone and photochemical precursors. These observational data are helpful to analyze the local ozone budget and its sensitivity to precursors with the help of an observation-based model (RACM2-LIM1). The observed ozone concentration was up to 121 ppbv during a photochemical episode from 1 to 8 October, when intensive ozone formation up to tens of ppbv/h was found. Ozone vertical measurement indicates the fast ozone production is happening throughout the planetary boundary layer (PBL), which is an important source of morning ozone increase resulting in ozone pollution. An explicit case study is performed to reveal the diurnal feature of instantaneous ozone production rate (P(Ox)) and accumulative P(Ox) based on the O3-NOx-VOC sensitivity, ROx radical primary production rate (P (ROx)), and LN/Q for three cases including ozone pollution and attainment periods. Results show that nitrogen oxides (NOx = NO + NO2) reduction have positive and negative impact on local ozone production from one pollution episode to the other, which indicates the complexity of O3-precursors sensitivity and difficulty to control ozone pollution in Shenzhen. Finally, comparison among measurements in other campaigns provides additional evidence on local ozone production sensitivity on NOx and anthropogenic volatile organic compounds (AVOCs) with respect to a temporal and spatial change. The NOx reduction in Shenzhen has led to higher ozone production from 2015 to 2018 given the nearly constant VOC. However, the ozone mitigation would be benefit from further NOx reduction in the conditions of 2018.

Vertical Characteristics of Winter Ozone Distribution within the Boundary Layer in Shanghai Based on Hexacopter Unmanned Aerial Vehicle Platform

Ozone is an important secondary air pollutant and plays different significant roles in regulating the formation of secondary organic aerosols. However, the characteristics of winter vertical ozone distributions have rarely been studied. In the winter of 2017, field experiments were performed in Shanghai, China using hexacopter unmanned aerial vehicle (UAV) platforms. The vertical profiles of ozone were obtained from 0–1200 m above the ground level. Results show that the UAV observations were reliable to capture the vertical variations of ozone. Vertical ozone profiles in the winter are classified into four categories: (1) well-mixed profile, (2) altitudinal increasing profile, (3) stratification profile, and (4) spike profile. Results show that although the average surface ozone level was relatively low, strong ozone variability and high ozone concentrations occurred at the upper air. The maximum observed ozone concentration was 220 ppb. In addition, using meteorological profiles and backward trajectories, we found that the ozone elevation aloft can be attributed to the downward transport of air flow from higher altitudes. Furthermore, ozone accumulation in the winter could be influenced by the horizontal transport of air masses for the northern part of China. This study successfully used hexacopter UAV platforms to perform vertical observations within the boundary layer. This provides systematic classification of winter ozone distribution within the boundary layer.

On ground truth in cross-border ozone transport

ABSTRACT Cross-border transport of ozone is one of the most contentious issues of air pollution management in the U.S. Yet, both the modeling and observational studies are lacking. Models are normally validated by comparing predicted and observed ozone concentrations. However, proper validation of cross-border transport model requires a comparison of predictions against observation-based benchmarks of cross-border ozone transport. Such benchmarks are unavailable, as published observation-based studies always deal only with a combination of local production and cross-border transport, not a cross-border transport itself. We show how to extract necessary benchmarks from observations of rural monitoring sites near state borders. On example of the western border of New York, we find that in about two-thirds of the most polluted days all the ozone came in a steady cross-border inflow after previously passing over one or more large urban areas to the west. In all the enumerated days with direct cross-border inflow, daily maximum 8-hr concentrations of ozone just upwind of the border were over 60 ppb, with an average value of 68 ppb, just short of the 70 ppb ozone regulatory threshold, information also useful to state air pollution authorities. Implications: The purpose of the cross-border ozone pollution models is to predict cross-border transport of ozone, so the ability of the model to accurately represent observed ozone concentrations is necessary but not sufficient for model validation. The accuracy of predicted ozone concentrations is not necessarily the same as the accuracy of the predictions of ozone transport. Proper model validation requires comparisons against observation-based benchmarks of cross-border transport. Such observations, so far absent, can be obtained from rural monitoring sites near state borders, as illustrated by the example of western New York.

Quantification of the impact of the offshore petrochemical industrial park on ambient ozone using photochemical grid modeling and assessment monitoring.

This study integrated the results of photochemical grid modeling and assessment monitoring to quantify the impact of the offshore petrochemical industrial park (OPIP), with area of 26.03km2, on ambient ozone in a coastal region of Taiwan. A highly repetitive ozone-spreading phenomenon in the adjacent OPIP area was observed, which shows that ozone spreading follows a clear cycle between offshore and inland areas during the prevailing periods of ozone events (≥120 ppb). The incremental ratio of ambient ozone for the OPIP on ozone event days during the southwest and northeast monsoons in 2011-2016 ranged from 1.05 to 1.25 (average = 1.15) and 1.04-1.27 (average = 1.17), respectively. Data from ten photochemical assessment monitoring stations surrounding the OPIP in 2016 showed that the ratio of monthly average concentrations of volatile organic compounds (VOCs) during the northeast monsoon to the southwest monsoon was approximately 1.5. The ratio of the monthly latent incremental amount of ozone to the total volatile organic amount in the same month during the northeast and southwest monsoons was in the ranges of approximately 0.84-0.97 and 1.01-1.12, respectively. Moreover, the latent incremental amount of ozone during the daytime was greater than that at night. The results indicate that the observed ozone concentration increases as the latent incremental amount of ozone or ambient VOCs decreases.

Atmospheric patterns in relationship with observed ozone concentrations in the Phoenix, Arizona, metropolitan area during the North American Monsoon

Phoenix, Arizona is a designated ozone nonattainment area by the United States Environmental Protection Agency (EPA) and is susceptible to unhealthy ozone during the summer North American Monsoon. This study identifies common July and August synoptic environments linked with daily exceedances and non-exceedances of the EPA National Ambient Air Quality Standard (NAAQS). Results indicate a common weather pattern for exceeding the NAAQS consisting of 1) an amplified high-pressure ridge over the Four Corners region causing 500 hPa heights to often exceed 5910 m, 2) surface afternoon temperatures typically rising over 40 °C, 3) lighter wind speeds in the planetary boundary layer (PBL) under four ms−1, and 4) a distinct and persistent light easterly flow regime from 700 to 500 hPa. The last feature would counter local mountain-valley winds in the upper PBL to promote ozone accumulation aloft and subsequent fumigation. Conversely, non-exceedance days are associated with 1) West Coast troughing and 500 hPa geopotential heights between 5.9 and 21.4 m lower, 2) afternoon PBL temperatures on average 0.8 °C–2.2 °C cooler, 3) faster afternoon westerly flow at 925 and 850 hPa over four ms−1, and 4) westerly flow in general at and above 925 hPa, aligning with the daytime mountain-valley circulation. Furthermore, a secondary non-exceedance pattern was identified. This less frequent pattern has moist southeast flow and is recognized for bringing widespread convective storm activity to central Arizona, including the PNA, based on prior research.

Exploring ozone pollution in Chengdu, southwestern China: A case study from radical chemistry to O3-VOC-NOx sensitivity

We present the in-situ measurements in Chengdu, a major city in south west of China, in September 2016. The concentrations of ozone and its precursor were measured at four sites. Although the campaign was conducted in early autumn, up to 100 ppbv (parts per billion by volume) daily maximum ozone was often observed at all sites. The observed ozone concentrations showed good agreement at all sites, which implied that ozone pollution is a regional issue in Chengdu. To better understand the ozone formation in Chengdu, an observation based model is used in this study to calculate the ROx radical concentrations (ROx = OH + HO2 + RO2) and ozone production rate (P(O3)). The model predicts OH daily maximum is in the range of 4–8 × 106 molecules cm−3, and HO2 and RO2 are in the range of 3–6 × 108 molecules cm−3. The modelled radical concentrations show a distinct difference between ozone pollution and attainment period. The relative incremental reactivity (RIR) results demonstrate that anthropogenic VOCs reduction is the most efficient way to mitigate ozone pollution at all sites, of which alkenes dominate >50% of the ozone production. Empirical kinetic modelling approach shows that three out of four sites are under the VOC-limited regime, while Pengzhou is in a transition regime due to the local petrochemical industry. The ozone budget analysis showed that the local ozone production driven by the photochemical process is important to the accumulation of ozone concentrations.

The Role of Medium-sized Cities for Global Tropospheric Ozone Levels

Brazilian medium-sized cities are those showing highest growing rates in the last decades, above 3% annually. To call attention to the consequences of such strong urban growth on air quality, measurements of ozone concentrations were comparatively performed in Londrina (a growing medium-sized city), Curitiba (a big city) and São Paulo (a megacity). Particularly to the cities of Londrina and São Paulo, both are located at similar latitude (–23.5). Surprisingly, the findings of this study indicated that, there are periods of the year in which the average ozone concentration measured in Londrina can be even higher than those found in large urban areas like São Paulo. The average ozone concentrations at three medium cities are close to those found in São Paulo. It is suggested that the local meteorological conditions (temperature, cloud cover, relative humidity and wind speed), as well as the local chemical regime, could explain the differences in the observed ozone concentrations. As the number of medium-sized urban areas is increasing around the world, especially in South America, special attention should be given by policy makers when defining new air quality monitoring networks and the regulation of new areas planned for the purpose of industrial development.

Satellite constraint on the tropospheric ozone radiative effect

AbstractTropospheric ozone directly affects the radiative balance of the Earth through interaction with shortwave and longwave radiation. Here we use measurements of tropospheric ozone from the Tropospheric Emission Spectrometer satellite instrument, together with chemical transport and radiative transfer models, to produce a first estimate of the stratospherically adjusted annual radiative effect (RE) of tropospheric ozone. We show that differences between modeled and observed ozone concentrations have little impact on the RE, indicating that our present‐day tropospheric ozone RE estimate of 1.17 ± 0.03 W m−2 is robust. The RE normalized by column ozone decreased between the preindustrial and the present‐day. Using a simulation with historical biomass burning and no anthropogenic emissions, we calculate a radiative forcing of 0.32 W m−2 for tropospheric ozone, within the current best estimate range. We propose a radiative kernel approach as an efficient and accurate tool for calculating ozone REs in simulations with similar ozone abundances.

Tropospheric Ozone Response on Climate Change in Malaysia

Ozone at the tropospheric level is considered as pollutants and harms the human health. As the chemistry of tropospheric ozone is sensitive to solar radiation and temperature, one may expect significant changes to the tropospheric ozone variability due to climate change. In this study, the authors have explored the impact of regional climate change to the tropospheric ozone in a number of urban, rural and remote areas in Malaysia. This paper aims to develop a climate change scenario for A2 emissions over Malaysia using RCM PRECIS model and used the climate output as input to CiTTyCAT, a tropospheric chemistry model. At the end of this century, the surface temperature and precipitation were found to increase both during wet season (winter monsoon) and dry season (summer monsoon). In response to climate change relative to the observed ozone concentrations in year 2008, tropospheric ozone concentrations have been found to increase in urban areas (Kuala Lumpur, Sg. Petani and Kota Kinabalu), while in rural and remote areas (Kapit and Danum Valley) concentrations have been found to decrease. These projections were observed in both seasons. This study has suggested that tropospheric ozone sensitivity to climate change shows a degree of response variability.

Retrospective health impact assessment for ozone pollution in Mexico City from 1991 to 2011

Air pollution is the main environmental issue in Mexico City, where ozone is one of the most damaging pollutants for human health. In this work we present a retrospective health impact assessment (HIA) study split up by age groups for evaluating the benefits of ozone regulatory strategies from 1991 to 2011 in Mexico City. Since people move from one place to another during the day, which may affect their potential exposure to pollutants, we consider time-dependant spatial population distributions during the day. Ozone data is made up of observations taken with hourly frequency from January 1, 1991 to December 31, 2011, at approximately 22 stations of the monitoring network of Mexico City. Interpolated values for unknown locations are also taken into account in the HIA. The Cressman objective analysis method is applied for interpolating the observed ozone concentrations from monitoring stations to grids of convenient resolution. We demonstrate that different age groups present different spatial patterns of exposure, being the working-age people (between 18 and 64 years) the most benefited. We also confirm the hypothesis that, in general, people move to less polluted regions during the day.

Climatological simulations of ozone and atmospheric aerosols in the Greater Cairo region

An integrated chemistry-climate model (RegCM4-CHEM) simulates present-day climate, ozone and tropospheric aerosols over Egypt with a focus on Greater Cairo (GC) region. The densley populated GC region is known for its severe air quality issues driven by high levels of anthropogenic pollution in conjuction with natural sources such as dust and agricultural burning events. We find that current global emission inventories underestimate key pollutants such as nitrogen oxides and anthropogenic aerosol species. In the GC region, average-ground-based NO2 observations of 40-60 ppb are substantially higher than modeled estimates (5-10 ppb), likely due to model grid resolution, improper boundary layer representation, and poor emissions inventories. Observed ozone concentrations range from 35 ppb (winter) to 80 ppb (summer). The model reproduces the seasonal cycle fairly well, but modeled summer ozone is understimated by approximately 15 ppb and exhibits little interannual variability. For aerosols, springtime dust events dominate the seasonal aerosol cycle. The chemistry-climate model captures the springtime peak aerosol optical depth (AOD) of 0.7-1 but is slightly greater than satellite-derived AOD. Observed AOD decreases in the summer and increases again in the fall due to agricultural burning events in the Nile Delta, yet the model underestimates this fall observed AOD peak, asmore » standard emissions inventories underestimate this burning and the resulting aerosol emissions. Our comparison of modeled gas and particulate phase atmospheric chemistry in the GC region indicates that improved emissions inventories of mobile sources and other anthropogenic activities are needed to improve air quality simulations in this region.« less

Distribution of Ozone over Urban Kolkata: Observed vs. UAM-V Prediction

Vehicular pollution, emissions due to burning of fossil fuel from industries and nonpoint sources in Kolkata are major sources of air pollution characterized by oxides of Nitrogen (NOx) and volatile organic compounds (VOCs). These pollutants are also responsible for the secondary ozone formation based on their reactivities. In the present study ozone has been monitored hourly every month in residential, industrial, traffic intersections, and petrol pumps in the urban area of Kolkata along with eight hourly nonoxygenated VOCs, carbonyls and NOx. Urban Airshed Model (UAM-V) has been used to simulate ozone on January 14, 2008 in Kolkata’s urban Area. Results of predicted ground level ozone have been in agreement with observed ozone concentrations.

Houston’s rapid ozone increases: preconditions and geographic origins

Many of Houston's highest 8-h ozone (O3) peaks are characterised by increases in concentrations of at least 40 ppb in 1 h, or 60 ppb in 2 h. These rapid increases are called non-typical O3 changes (NTOCs). In 2004, the Texas Commission on Environmental Quality (TCEQ) developed a novel emissions control strategy aimed at eliminating NTOCs. The strategy limited routine and short-term emissions of ethene, propene, 1,3-butadiene and butene isomers, collectively called highly reactive volatile organic compounds (HRVOCs), which are released from petrochemical facilities. HRVOCs have been associated with NTOCs through field campaigns and modelling studies. This study analysed wind measurements and O3, formaldehyde (HCHO) and sulfur dioxide (SO2) concentrations from 2000 to 2011 at 25 ground monitors in Houston. NTOCs almost always occurred when monitors were downwind of petrochemical facilities. Rapid O3 increases were associated with low wind speeds; 75 % of NTOCs occurred when the 3-h average wind speed preceding the event was less than 6.5 km h-1. Statistically significant differences in HCHO concentrations were seen between days with and without NTOCs. Early afternoon HCHO concentrations were greater on NTOC days. In the morning before an observed NTOC event, however, there were no significant differences in HCHO concentrations between days with and without NTOCs. Hourly SO2 concentrations also increased rapidly, exhibiting behaviour similar to NTOCs. Oftentimes, the SO2 increases preceded a NTOC. These findings show that, despite the apparent success of targeted HRVOC emission controls, further restrictions may be needed to eliminate the remaining O3 events.

Modeling analysis of the impact of anthropogenic emission sources on ozone concentration over selected urban areas in Texas

Due to several regional–scale high ozone episodes that impacted the urban areas in south and central Texas over the past decade, the Texas Commission on Environmental Quality (TCEQ) has designated several urban regions as near non–attainment areas. A regional photochemical modeling experiment was set up to simulate a high ozone episode of September 11–14, 2002 in order to evaluate the impact of various anthropogenic emissions sources on ozone concentrations. The base case simulation showed reasonable model performance by capturing the peaks and the diurnal variability of observed ozone concentrations within the modeling domain. A comprehensive impact assessment of anthropogenic emissions from various source categories to the 8–hour ozone concentration was evaluated for each of the urban areas within the study region. Through a source apportionment analysis of emissions influencing the 8– hour ozone concentrations, NOx and VOC limited areas were identified. The model results showed that the net effect of all anthropogenic emissions was approximately 8.4 ppb in Victoria, 8.8 ppb in Corpus Christi, and 31.2 and 34.1 ppb in Austin and San Antonio, respectively. Impact of major emissions source categories differed regionally with ozone concentrations in Austin and San Antonio mainly influenced by mobile sources, while Corpus Christi and Victoria were largely impacted by long–range transport of ozone. On a local scale, Corpus Christi was also impacted by non–road sources, while Victoria was influenced by point sources. Ozone sensitivity analysis showed higher sensitivity towards VOC within the urban cores of Austin, San Antonio, and Corpus Christi, while the overall modeling regions showed higher NOx sensitivity. This would indicate that both NOx and VOC emissions reduction plans need to be developed and implemented for the mitigation of regional and urban ozone. The results also revealed that biogenic emissions played an important role in the urban regions of south and central Texas.

Can a global model reproduce observed trends in summertime surface ozone levels?

Abstract. Quantifying trends in surface ozone concentrations is critical for assessing pollution control strategies. Here we use observations and results from a global chemical transport model to examine the trends (1991–2005) in daily maximum 8-h average concentrations in summertime surface ozone at rural sites in Europe and the United States (US). We find a decrease in observed ozone concentrations at the high end of the probability distribution at many of the sites in both regions. The model attributes these trends to a decrease in local anthropogenic ozone precursors, although simulated decreasing trends are overestimated in comparison with observed ones. The low end of observed distribution show small upward trends over Europe and the western US and downward trends in Eastern US. The model cannot reproduce these observed trends, especially over Europe and the western US. In particular, simulated changes between the low and high end of the distributions in these two regions are not significant. Sensitivity simulations indicate that emissions from far away source regions do not affect significantly summer ozone trends at both ends of the distribution in both Europe and US. Possible reasons for discrepancies between observed and simulated trends are discussed.

The impact of transported ozone-rich air on the atmospheric ozone content following the 26 January 2001 and 7 March 2006 Gujarat earthquakes

The contribution of transport processes to the observed ozone concentration following the 26 January 2001 and 7 March 2006 earthquakes in the Kutch region of Gujarat is presented. The analysis of back trajectories at different altitudes and vertical pressure velocities at the tropopause indicated the transport of ozone-rich air from higher latitudes in the tropospheric and lower stratospheric regions apart from stratospheric intrusion of ozone into the troposphere along the path of the back trajectory and its transport to the epicentre during these earthquakes.

A layer of ozone detected in the nightside upper atmosphere of Venus

To date, ozone has only been identified in the atmospheres of Earth and Mars. This study reports the first detection of ozone in the atmosphere of Venus by the SPICAV ultraviolet instrument onboard the Venus Express spacecraft. Venusian ozone is characterized by a vertically confined and horizontally variable layer residing in the thermosphere at a mean altitude of 100 km, with local concentrations of the order of 10 7–10 8 molecules cm −3. The observed ozone concentrations are consistent with values expected for a chlorine-catalyzed destruction scheme, indicating that the key chemical reactions operating in Earth’s upper stratosphere may also operate on Venus.