Low Ozone Values Research Articles

Simulating the Volcanic Sulfate Aerosols From the 1991 Eruption of Cerro Hudson and Their Impact on the 1991 Ozone Hole

AbstractThe Chilean volcano Cerro Hudson erupted between August 8th and 15th, 1991, injecting between 1.7 and 2.9 Tg of SO2 into the upper troposphere and lower stratosphere. We simulate this injection using the Goddard Earth Observing System Earth system model with detailed sulfur chemistry and sectional aerosol microphysics, focusing on the resulting aerosols and their contribution to the 1991 Antarctic Austral Springtime ozone hole. The simulations show a column ozone deficit (12 DU) in the Southern Hemisphere vortex collar region. The majority of this effect is between 10 and 20 km and due to heterogeneous chemistry. The model shows a 26% decrease in ozone from background levels at these altitudes, compared with in‐situ observations of a 50% decrease. Above 20 km, the dynamical response to the eruption also causes lower ozone values, a novel modeling result. This experiment highlights potential interactions between proposed solar radiation management geoengineering aerosols and volcanic eruptions.

The effects of gravity waves on ozone over the Tibetan Plateau

The ozone valley over the Tibetan Plateau (TP) has an important effect on global weather and climate. As a significant source of atmospheric gravity waves (GWs), TP is also a key area of global stratosphere-troposphere exchange (STE), yet the exploration of the causes of low ozone values over the TP has been scarce from the perspective of GW. In this paper, we used the hyperspectral Atmospheric Infrared Sounder (AIRS) data to extract GWs and deep convection over the TP and analyzed the statistical characteristics of ozone for corresponding events. The results show that: (1) The GWs observed by AIRS mainly occur in the mid-latitude region, with a maximum frequency of >10%, and their intensity varies with longitude. Three large-value regions have been identified on the coast of Southeast Asia, Central America, and Central Africa. (2) Most deep convection occurs in the Intertropical Convergence Zone (ITCZ), with three large value centers in the East Asian monsoon region, Central America and Central Africa. Among them, the Indian monsoon region, the Northwest Pacific region to the east of the Philippines, and the western side of the South China Sea (SCS) are the large-value areas within the East Asian monsoon region, with the maximum occurrence frequency exceeding 15%. (3) TP is a region with a large frequency of convective gravity waves. In most areas of the southern foothills of the TP, the frequency of GWs related to convection is 30%–50%. Almost all deep convection over the TP and its adjacent areas are accompanied by GWs, with a frequency of 60–90%. (4) The composite analysis results show that the occurrence of GWs or deep convection is accompanied by negative anomalies of ozone in most areas of the southern foothills of the TP, indicating a decrease in the integrated column amount of ozone. (5) By analyzing the anomaly distribution of meteorological elements such as cloud fraction, cloud top height, tropopause height, and outgoing longwave radiation (OLR), the results show a dual effect in the presence of GWs or deep convection. The effect involves not only an increased generation of clouds, conducive to convection but also elevated cloud top height, promoting the formation of high clouds, some even beyond the tropopause. In addition, the occurrence of GW or deep convection can also affect the tropopause height, strengthen convective activity, and facilitate the upward transfer of low-concentration ozone from the lower layer to the upper layer, thereby causing a decrease in the integrated column amount of ozone.

Assessing the influence of intertropical discontinuity on total column ozone variation over West Africa.

The focus of this study is to evaluate the influence of intertropical discontinuity (ITD) on the variation of total column ozone (TCO). Relevant information is supplied on the temporal and spatial variability of TCO along the ITD zone, which is an important factor influencing the earth's atmosphere. Several studies over the years have established the relationship and have influence several atmospheric processes on TCO. However, the relationship between intertropical discontinuity and TCO over West Africa has a gap. This study tends to examine the influence ITD has on TCO variation using the West African region as a case study. The study used wind, ozone, and dewpoint temperature data for the period between 1980 and 2019. To assess the variability and trend over the study region, several statistical methods were used, including Pearson correlation, Mann-Kendall, and linear regression model. The Mann-Kendall test shows an increasing trend throughout the months over the study region. Spatial analysis also revealed that regions north of the ITD have a higher concentration of TCO than the southern region of the ITD between April and September. However, ITD influence was more visible during the wet months of June to August (JJA) as the highest concentration of TCO was observed during this period across all latitude, but more deviation was observed between latitude 10 to 18° N, while the least occurrence is observed when ITD is at its minimum position in the month of December to February (DJF). The ACRV shows that 14° N exhibit the highest variation with a value of 4.84, while the deviation is also at its highest with value of 13.65. The monthly position of ITD for 40years was also analysed to observe the monthly deviation along the ITD region 40years, and the spatial distribution of TCO was analysed from January to December. It is of note that during the cause of this study, low-ozone values of 220DU are not found in the study region. The highest and the lowest value of TCO is 295 DU and 227 DU, respectively, with an average range of 68DU.

The Unusual Stratospheric Arctic Winter 2019/20: Chemical Ozone Loss From Satellite Observations and TOMCAT Chemical Transport Model

AbstractSatellite observations of relevant trace gases and meteorological data from ERA5 were used to describe the dynamics and chemistry of the spectacular Arctic 2019/20 winter/spring season. Exceptionally low total ozone values of slightly less than 220 DU were observed in mid‐March within an unusually large stratospheric polar vortex. Very high OClO and very low NO2 column amounts observed by GOME‐2A were indicative of unusually large active chlorine levels and significant denitrification, which likely contributed to large chemical ozone loss. Using results from the TOMCAT chemical transport model (CTM) and ozone observations from S5P/TROPOMI, GOME‐2 (total column), SCIAMACHY, and OMPS‐LP (vertical profiles), chemical ozone loss was evaluated and compared with the previous record Arctic winter 2010/11. The polar‐vortex‐averaged total column ozone loss in 2019/20 reached 88 DU (23%) and 106 DU (28%) based upon observations and model, respectively, by the end of March, which was similar to that derived for 2010/11. The maximum ozone loss (∼80%) observed by OMPS‐LP was near the 450 K potential temperature level (∼18 km altitude). Because of the larger polar vortex area in March 2020 compared to March 2011 (about 25% at 450 K), ozone mass loss was larger in Arctic winter 2019/20. It is shown that Arctic cap temperatures were at a record 40‐year low in winter, suggesting that Arctic cold winters are getting colder. Tropical UTLS temperatures show an apparent upward trend during the last two decades that may indicate a weakening of the Brewer‐Dobson circulation and strengthening of the polar vortex.

Arctic Ozone Depletion in 2019/20: Roles of Chemistry, Dynamics and the Montreal Protocol

AbstractWe use a three‐dimensional chemical transport model and satellite observations to investigate Arctic ozone depletion in winter/spring 2019/20 and compare with earlier years. Persistently, low temperatures caused extensive chlorine activation through to March. March‐mean polar‐cap‐mean modeled chemical column ozone loss reached 78 DU (local maximum loss of ∼108 DU in the vortex), similar to that in 2011. However, weak dynamical replenishment of only 59 DU from December to March was key to producing very low (<220 DU) column ozone values. The only other winter to exhibit such weak transport in the past 20 years was 2010/11, so this process is fundamental to causing such low ozone values. A model simulation with peak observed stratospheric total chlorine and bromine loading (from the mid‐1990s) shows that gradual recovery of the ozone layer over the past 2 decades ameliorated the polar cap ozone depletion in March 2020 by ∼20 DU.

Tropical Cyclones Reduce Ozone in the Tropopause Region Over the Western Pacific: An Analysis of 18 Years Ozonesonde Profiles

AbstractTyphoons play a key role in causing low ozone concentrations in the upper troposphere and lower stratosphere (UTLS) over the western Pacific. In this study, 18 years records (2000–2017) of balloon‐borne ozone measurements in Hong Kong (22.3°N, 114.2°E) and Naha (26.2°N, 127.7°E) are combined with trajectory calculations to quantitatively assess the impact of western Pacific typhoons on ozone in the UTLS. The results show that 46.3% (44.9%) of the ozone profiles in Hong Kong (Naha) are impacted by western Pacific typhoons from July to October, with negative ozone anomalies exceeding −20%. Vertical transport by intense typhoons affects 16.8% (18.8%) of the ozone profiles in Hong Kong (Naha) with even larger negative anomalies (<−40%). Vertical transport of tropical cyclones reduces ozone by about 20–60 ppbv compared to the mean ozone profile near the tropopause. Ozone values below 60 ppbv in the upper troposphere in Hong Kong and Naha are mainly caused by the uplift in the western Pacific typhoons and by horizontal transport within the Asian summer monsoon (ASM) anticyclone. The horizontal transport in the ASM anticyclone has larger contributions to the low ozone values measured over Hong Kong than over Naha.

Estudo numérico e observacional de um evento de diminuição da coluna total de ozônio de origem tropical no Sul do Brasil

A depletion event of 11% of the total ozone column over South Brazil was analyzed from observational data and numerical simulations. The meteorological fields resulting from the simulation did not show the presence of subtropical or polar jets over the study region. The real and simulated soundings showed the dryness at high and low tropospheric levels, pointing a stratospheric intrusion. The total ozone column values from ERA-5 reanalyses showed the maintenance of a region with low total ozone values in tropical latitudes and its advance over the study region, before and during the depletion event. The isentropic retro-trajectories of air parcels at different levels, obtained with the Hybrid Single Lagrangian Integrated Trajectory Model (HYSPLIT), confirmed the zonal transport from the tropical region over Southern Brazil. A combination of a cyclonic circulation at the 850 K stratospheric isentropic level and an intense anticyclonic circulation at the 440 K tropospheric level, over the depletion region, was identified as responsible for the tropopause lift and horizontal transport of ozone-rich air out of the column.

Dehydration and low ozone in the tropopause layer over the Asian monsoon caused by tropical cyclones: Lagrangian transport calculations using ERA-Interim and ERA5 reanalysis data

Abstract. Low ozone and high water vapour mixing ratios are common features in the Asian summer monsoon (ASM) anticyclone; however, low ozone and low water vapour values were observed near the tropopause over Kunming, China, within the ASM using balloon-borne measurements performed during the SWOP (sounding water vapour, ozone, and particle) campaign in August 2009 and 2015. Here, we investigate low ozone and water vapour signatures in the upper troposphere and lower stratosphere (UTLS) using FengYun-2D, FengYun-2G, and Aura Microwave Limb Sounder (MLS) satellite measurements and backward trajectory calculations. Trajectories with kinematic and diabatic vertical velocities were calculated using the Chemical Lagrangian Model of the Stratosphere (CLaMS) trajectory module driven by both ERA-Interim and ERA5 reanalysis data. All trajectory calculations show that air parcels with low ozone and low water vapour values in the UTLS over Kunming measured by balloon-borne instruments originate from the western Pacific boundary layer. Deep convection associated with tropical cyclones over the western Pacific transports ozone-poor air from the marine boundary layer to the cold tropopause region. Subsequently, these air parcels are mixed into the strong easterlies on the southern side of the Asian summer monsoon anticyclone. Air parcels are dehydrated when passing the lowest temperature region (< 190 K) at the convective outflow of tropical cyclones. However, trajectory calculations show different vertical transport via deep convection depending on the employed reanalysis data (ERA-Interim, ERA5) and vertical velocities (diabatic, kinematic). Both the kinematic and the diabatic trajectory calculations using ERA5 data show much faster and stronger vertical transport than ERA-Interim primarily because of ERA5's better spatial and temporal resolution, which likely resolves convective events more accurately. Our findings show that the interplay between the ASM anticyclone and tropical cyclones has a significant impact on the chemical composition of the UTLS during summer.

A data ensemble approach for real-time air quality forecasting using extremely randomized trees and deep neural networks

Six generalized machine learning (ML) ensemble models were developed to predict the real-time hourly ozone concentration of the following day. These models were used to forecast hourly ozone concentrations of the following day for all of 2017 in the city of Seoul, South Korea. To prepare the training dataset, it was referred to observed meteorology and air pollution parameters of the 2014–2016 period. The ensemble models fuse two regression models: a low-ozone peak model and a high-ozone model. For both, extremely randomized trees and deep neural networks were used. A regularization approach was also adopted that adjusts the model toward capturing higher ozone peaks by resampling the training dataset based on the peaks. Adopting the proposed ML ensemble forecasting method over single-model ML techniques as a part of mainstream practice for air quality forecasting will be beneficial for several reasons. For one, the proposed method, which captures daily maximum ozone concentrations during the high-ozone season (April–September), reduces the ozone peak prediction error by 5 to 30 ppb. In addition, compared to station-specific (independent) ML models with more frequent low-ozone values, models are trained with a uniformly distributed dataset, so they are more generalizable in nature. As a result, unlike station-specific models, they retain their accuracy (yearly IOA = 0.84–0.89) in all stations with an IOA increment. Proposed models also make predictions several times faster, requiring only one-time training for predicting an entire station network. Based on a categorical analysis of the training dataset, an algorithm was proposed for selecting the most suitable model for each month. The “best” model further improves the accuracy of both the ML ensemble and individual models by up to 2.4%. This study shows that the ML ensemble modeling approach is a fast, reliable, and robust technique that can benefit environmental decision-makers in urban regions.

Total Ozone over Vernadsky Antarctic Station: Ground-based and Satellite Measurements

Objective. Provide an analysis of the total ozone variations over Vernadsky Antarctic station (Faraday Base until 1996) from long-term ground-based and satellite series. Study the discrepancies between the data of different instruments. Methods. Data visualization followed by analysis, statistical treatment of the Vernadsky Dobson spectrophotometer observations and satellite total ozone series. Results. Satellite and ground-based measurements of total ozone over Vernadsky station have confirmed the stabilization in the ozone layer in the stratosphere over Antarctica from the early 2000s. British Faraday Base observations have retrieved an ozone spring maximum during the 1950s–1970s with a sharp decrease in the August–October values in the 1980s–1990s. That changed substantially total ozone seasonal cycle. Satellite overpasses and model data based on satellite measurements have been analyzed. It is shown that typical discrepancies between the Ozone Monitoring Instrument (OMI) model and the Vernadsky Dobson daily means are mainly in the range of 20 DU. Larger deviations are rare and are observed predominantly on the beginning and at the end of the observational season. Seasonal means and standard deviations for the model–Dobson differences were calculated that demonstrates worse correspondence of the OMI model with Vernadsky Dobson data during separate years, in particular 2009–2010. Conclusions. Both Dobson and satellite ozone data over Faraday/Vernadsky station have shown the total ozone decrease during the 1980s–1990s (mainly in spring) with a following stabilization since year 2000. Comparison between the ground-based data and models calculated from satellite measurements indicates better correspondence of the Dobson and GOME2 results relatively the OMI ones. There are evidences that individual Dobson measurements underestimate to some degree total ozone on the beginning of observational season at high solar zenith angles and the low total ozone values.

Temporal Variations in the Vertical Distribution of Stratospheric Ozone over Obninsk from Lidar Data

The results of lidar measurements of ozone profiles over Obninsk in the altitude range of 12–35 km in 2012–2016 are presented. Temporal variations in total ozone in the above altitude range and seasonal variations in the vertical distribution of ozone are considered. Basic attention is paid to the analysis of ozone profile variations on the daily and weekly scales. The backtrajectory analysis demonstrated that in most cases the formation of layers with low or high ozone values is explained by the direction of meridional advection. Cross-correlation coefficients for the variations in ozone and temperature relative to the current monthly mean variations are calculated. Rather high values of correlation coefficients (~0.4–0.6) are obtained for summer in the low stratosphere (100 and 160 hPa) and for winter in the upper troposphere (50 and 20 hPa). In general, variations in ozone profiles are consistent with available climatologic data.

Low modeled ozone production suggests underestimation of precursor emissions (especially NO<sub><i>x</i></sub>) in Europe

Abstract. High surface ozone concentrations, which usually occur when photochemical ozone production takes place, pose a great risk to human health and vegetation. Air quality models are often used by policy makers as tools for the development of ozone mitigation strategies. However, the modeled ozone production is often not or not enough evaluated in many ozone modeling studies. The focus of this work is to evaluate the modeled ozone production in Europe indirectly, with the use of the ozone–temperature correlation for the summer of 2010 and to analyze its sensitivity to precursor emissions and meteorology by using the regional air quality model, the Comprehensive Air Quality Model with Extensions (CAMx). The results show that the model significantly underestimates the observed high afternoon surface ozone mixing ratios (≥ 60 ppb) by 10–20 ppb and overestimates the lower ones (< 40 ppb) by 5–15 ppb, resulting in a misleading good agreement with the observations for average ozone. The model also underestimates the ozone–temperature regression slope by about a factor of 2 for most of the measurement stations. To investigate the impact of emissions, four scenarios were tested: (i) increased volatile organic compound (VOC) emissions by a factor of 1.5 and 2 for the anthropogenic and biogenic VOC emissions, respectively, (ii) increased nitrogen oxide (NOx) emissions by a factor of 2, (iii) a combination of the first two scenarios and (iv) increased traffic-only NOx emissions by a factor of 4. For southern, eastern, and central (except the Benelux area) Europe, doubling NOx emissions seems to be the most efficient scenario to reduce the underestimation of the observed high ozone mixing ratios without significant degradation of the model performance for the lower ozone mixing ratios. The model performance for ozone–temperature correlation is also better when NOx emissions are doubled. In the Benelux area, however, the third scenario (where both NOx and VOC emissions are increased) leads to a better model performance. Although increasing only the traffic NOx emissions by a factor of 4 gave very similar results to the doubling of all NOx emissions, the first scenario is more consistent with the uncertainties reported by other studies than the latter, suggesting that high uncertainties in NOx emissions might originate mainly from the road-transport sector rather than from other sectors. The impact of meteorology was examined with three sensitivity tests: (i) increased surface temperature by 4 ∘C, (ii) reduced wind speed by 50 % and (iii) doubled wind speed. The first two scenarios led to a consistent increase in all surface ozone mixing ratios, thus improving the model performance for the high ozone values but significantly degrading it for the low ozone values, while the third scenario had exactly the opposite effects. Overall, the modeled ozone is predicted to be more sensitive to its precursor emissions (especially traffic NOx) and therefore their uncertainties, which seem to be responsible for the model underestimation of the observed high ozone mixing ratios and ozone production.

Cross tropopause flux observed at sub-daily scales over the south Indian monsoon regions

The effect of deep convection on the thermal structure and dynamics of the tropical tropopause at sub daily scales is investigated using data from radiosondes launched over two sites in the Indian Monsoon region (Gadanki (13.5°N, 79.2°E) and Trivandrum (8.5°N, 76.9°E)) conducted between December 2010 and March 2014. The data from these soundings are classified into 5 convective categories based on the past, present and future cloudiness over the launching region after the radiosonde has reached tropopause altitude. They are denoted as category 1 (no convection), category 2 (convection may occur in any of the next 3h), category 3 (convection occurred prior 3h), category 4 (convection terminated within 3h of launching) and category 5 (convection persistent throughout the considered period). The anomalies from the background in temperature, relative humidity and wind speed are grouped into the aforementioned five different convective categories for both the stations. Cooling and moisture anomalies are found during the active convection (category 5). The horizontal wind speed showed a strong anomaly indicating the presence of synoptic scale features. Vertical wind obtained simultaneously from the MST radar over Gadanki clearly showed strong updraft during the active convection. The ozone profiles from ozonesondes launched during the same period are also segregated according to the above convective categories. During the active convection, high and low ozone values are found in the upper troposphere and the lower troposphere, respectively. The cross tropopause ozone mass flux and vertical wind at the tropopause and convective outflow level estimated from the ozonesonde, and MST radar/ERA-Interim data showed positive values indicating the transport of ozone between troposphere and stratosphere during deep convection. Similarly, the total mass flux crossing the cold point tropopause over Gadanki showed upward flux during the active convection. The variability of the cross tropopause mass flux is found to be higher over Gadanki compared to Trivandrum.

Impact of typhoons on the composition of the upper troposphere within the Asian summer monsoon anticyclone: the SWOP campaign in Lhasa 2013

Abstract. In the frame of the SWOP (sounding water vapour, ozone, and particle) campaign during the Asian summer monsoon (ASM), ozone and water vapour profiles were measured by balloon-borne sensors launched from Lhasa (29.66° N, 91.14° E, elevation 3650 m), China, in August 2013. In total, 24 soundings were launched, nearly half of which show strong variations in the relationship between ozone and water vapour in the tracer–tracer correlation in the upper troposphere and lower stratosphere (UTLS). For each sounding, 20-day backward trajectories were calculated using the trajectory module of the Chemical Lagrangian Model of the Stratosphere (CLaMS) to analyse these variations. The trajectory calculations demonstrate that three tropical cyclones (tropical storm Jebi, typhoons Utor and Trami), which occurred over the western Pacific Ocean during August 2013, had a considerable impact on the vertical distribution of ozone and water vapour by uplifting marine air masses to altitudes of the ASM anticyclone. Air parcels subsequently arrived at the observation site via two primary pathways: firstly via direct horizontal transport from the location of the typhoon to the station within approximately 3 days, and secondly via transport following the clockwise wind flow of the ASM within a timescale of 1 week. Furthermore, the interplay between the spatial position of the ASM anticyclone and tropical cyclones plays a key role in controlling the transport pathways of air parcels from the boundary layer of the western Pacific to Lhasa in horizontal and vertical transport. Moreover, the statistical analysis shows that the strongest impact by typhoons is found at altitudes between 14.5 and 17 km (365–375 K). Low ozone values (50–80 ppbv) were observed between 370 and 380 K due to the strong vertical transport within tropical cyclones.

Extremely low total ozone values over the northern Ural and Siberia in the end of January 2016

Extremely low total ozone values over the northern Ural and Siberia in the end of January 2016

Transport effects on the vertical distribution of tropospheric ozone over western India

AbstractIn situ tropospheric ozone measurements by balloon‐borne electrochemical concentration cell (ECC) sensors above Ahmedabad in western India from May 2003 to July 2007 are presented, along with an analysis of the transport processes responsible for the observed vertical ozone distribution. This analysis is supported by 12 day back trajectory calculations using the FLEXPART Lagrangian particle dispersion model. Lowest ozone (~20 ppbv) is observed near the surface during September at the end of the Asian summer monsoon season. Average midtropospheric (5–10 km above sea level) ozone is greatest (70–75 ppbv) during April–June and lowest (40–50 ppbv) during winter. Ozone variability is greatest in the upper troposphere with higher ozone during March–May. The FLEXPART retroplume results show that the free tropospheric vertical ozone distribution above this location is affected by long‐range transport from the direction of North Africa and North America. Ozone levels are also affected by transport from the stratosphere particularly during March–April. The lower tropospheric (<3 km) ozone distribution during the Asian summer monsoon is affected by transport from the Indian Ocean via the east coast of Africa and the Arabian Sea. Influence from deep convection in the upper troposphere confined over central Asia has been simulated by FLEXPART. Lower ozone levels are observed during August–November than in any other season at 10–14 km above sea level. These in situ observations are in contrast to other studies based on satellite data which show that the lowest ozone values at these altitudes occur during the Asian summer monsoon.

Fundamental differences between Arctic and Antarctic ozone depletion.

Antarctic ozone depletion is associated with enhanced chlorine from anthropogenic chlorofluorocarbons and heterogeneous chemistry under cold conditions. The deep Antarctic "hole" contrasts with the generally weaker depletions observed in the warmer Arctic. An unusually cold Arctic stratospheric season occurred in 2011, raising the question of how the Arctic ozone chemistry in that year compares with others. We show that the averaged depletions near 20 km across the cold part of each pole are deeper in Antarctica than in the Arctic for all years, although 2011 Arctic values do rival those seen in less-depleted years in Antarctica. We focus not only on averages but also on extremes, to address whether or not Arctic ozone depletion can be as extreme as that observed in the Antarctic. This information provides unique insights into the contrasts between Arctic and Antarctic ozone chemistry. We show that extreme Antarctic ozone minima fall to or below 0.1 parts per million by volume (ppmv) at 18 and 20 km (about 70 and 50 mbar) whereas the lowest Arctic ozone values are about 0.5 ppmv at these altitudes. At a higher altitude of 24 km (30-mbar level), no Arctic data below about 2 ppmv have been observed, including in 2011, in contrast to values more than an order of magnitude lower in Antarctica. The data show that the lowest ozone values are associated with temperatures below -80 °C to -85 °C depending upon altitude, and are closely associated with reduced gaseous nitric acid concentrations due to uptake and/or sedimentation in polar stratospheric cloud particles.

Observed atmospheric total column ozone distribution from SCIAMACHY over Peninsular Malaysia

The increase in atmospheric ozone has received great attention because it degrades air quality and brings hazard to human health and ecosystems. The aim of this study was to assess the seasonal variations of ozone concentrations in Peninsular Malaysia from January 2003 to December 2009 using Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY). Level-2 data of total column ozone WFMD version 1.0 with spatial resolution 1° × 1.25° were acquired through SCIAMACHY. Analysis for trend of five selected sites exhibit strong seasonal variation in atmospheric ozone concentrations, where there is a significant difference between northeast monsoon and southwest monsoon. The highest ozone values occurred over industrial and congested urban zones (280.97 DU) on August at Bayan Lepas. The lowest ozone values were observed during northeast monsoon on December at Subang (233.08 DU). In addition, the local meteorological factors also bring an impact on the atmospheric ozone. During northeast monsoon, with the higher rate of precipitation, higher relative humidity, low temperature, and less sunlight hours let to the lowest ozone concentrations. Inversely, the highest ozone concentrations observed during southwest monsoon, with the low precipitation rate, lower relative humidity, higher temperature, and more sunlight hours. Back trajectories analysis is carried out, in order to trace the path of the air parcels with high ozone concentration event, suggesting cluster of trajectory (from southwest of the study area) caused by the anthropogenic sources associated with biogenic emissions from large tropical forests, which can make important contribution to regional and global pollution.

HCl and ClO profiles inside the Antarctic vortex as observed by SMILES in November 2009: comparisons with MLS and ACE-FTS instruments

Abstract. We present vertical profiles of hydrogen chloride (HCl) and chlorine monoxide (ClO) as observed by the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station (ISS) inside the Antarctic vortex on 19–24 November 2009. The SMILES HCl value reveals 2.8–3.1 ppbv between 450 K and 500 K levels in potential temperature (PT). The high value of HCl is highlighted since it is suggested that HCl is a main component of the total inorganic chlorine (Cly), defined as Cly ≃ HCl + ClO + chlorine nitrate (ClONO2), inside the Antarctic vortex in spring, owing to low ozone values. To confirm the quality of two SMILES level 2 (L2) data products provided by the Japan Aerospace Exploration Agency (JAXA) and Japan's National Institute of Information and Communications Technology (NICT), vis-à-vis the partitioning of Cly, comparisons are made using other satellite data from the Aura Microwave Limb Sounder (MLS) and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). HCl values from the SMILES NICT L2 product agree to within 10% (0.3 ppbv) with the MLS HCl data between 450 and 575 K levels in PT and with the ACE-FTS HCl data between 425 and 575 K. The SMILES JAXA L2 product is 10 to 20% (0.2–0.5 ppbv) lower than that from MLS between 400 and 700 K and from ACE-FTS between 500 and 700 K. For ClO in daytime, the difference between SMILES (JAXA and NICT) and MLS is less than ±0.05 ppbv (100 %) between 500 K and 650 K with the ClO values less than 0.2 ppbv. ClONO2 values as measured by ACE-FTS also reveal 0.2 ppbv at 475–500 K level, resulting in the HCl / Cly ratios of 0.91–0.95. The HCl / Cly ratios derived from each retrieval agree to within −5 to 8 % with regard to their averages. The high HCl values and HCl / Cly ratios observed by the three instruments in the lower stratospheric Antarctic vortex are consistent with previous observations in late Austral spring.

Extreme ozone loss over the Northern Hemisphere high latitudes in the early 2011

ABSTRACTThe satellite ozone data comprising The New Zealand National Institute of Water and Atmospheric Research (NIWA) total ozone database version 2.7, total ozone by the Ozone Monitoring Instrument (OMI) spectrophotometer on the Aura platform, and the ozone mixing ratios by SBUV/2 measurements on The National Oceanic and Atmospheric Administration (NOAA) platforms are analysed for ozone variability over the sunlit part of the Northern Hemisphere polar region. An extended area, with unusually low ozone values, is observed in a two-month period beginning in mid February 2011. The total area with extremely depleted total ozone reached the maximum at the end of March 2011, equal to ~11×106 km2. The area is even larger in the lower/mid stratosphere. A multiple regression model is proposed to attribute the polar total ozone variability to various chemical and dynamical ozone forcings. The model reproduces the ozone loss in early 2011 and the overall picture of the ozone long-term changes. The extreme ozone decline in 2011 could be attributed to the long-lasting period with low stratospheric temperature (<195 K), weaker than the normal Brewer-Dobson circulation, and the Arctic Oscillation in a strong positive phase. A deficit of total ozone in the following summer months (June–July–August), after the total ozone decline in March, was predicted and supported by later OMI observations.