Search

Ozone is one of the key atmospheric trace gases that protects life on Earth from harmful solar ultraviolet radiation. The importance of ozone and its influence on various atmospheric processes led ...

Using satellite data and reanalysis data, the characteristics and mechanisms of the formation of an ozone “mini-hole” in the atmosphere over Siberia in the winter of 2015–2016 have been investigated. The relationship between the regional negative anomaly of the total ozone content (TOC), reaching –140 Dobson units, with atmospheric blocking was established. The TOC anomaly was mainly due to a decrease in the ozone content in the lower stratosphere, reaching 50% near the 70 hPa level. With the key contribution of atmospheric dynamic processes to the formation of the ozone “mini-hole,” the possibility of the contribution of ozone destruction in heterogeneous reactions on the surface of polar stratospheric clouds, due to a strong decrease in temperature in the stratosphere above the blocking region, was noted.

The review is compiled on the basis of the results of operation of the total ozone (TO) monitoring system in the CIS and Baltic countries functioning in the operational mode at the Central Aerological Observatory (CAO). The monitoring system uses data from the national network equipped with M-124 filter ozonometers being under the methodological supervision of the Main Geophysical Observatory. The quality of the functioning of the entire system is operationally controlled in CAO based on the OMI satellite equipment observations (NASA, USA). Basic TO observation data are generalized for each month of the first quarter of 2021 and for the first quarter. Data of routine observations of surface ozone values in the Moscow region are also presented.

This article aims to realize the combined application of satellite remote sensing data and Lidar data fusion of atmospheric ozone in the ozone distribution prediction in western China. Firstly, the ozone remote sensing data and Lidar vertical monitoring data detected by ozone monitoring instruments are collected from various provinces in western China; the recurrent neural network (RNN) model based on the gated recurrent unit and the convolutional neural network (CNN) model based on time series are constructed and integrated to obtain the RNN–CNN model for ozone concentration prediction, and the prediction performance is compared with that of the RNN and CNN model. Satellite remote sensing data show that the total ozone concentration in western China has obvious spatial distribution characteristics, and can be elevated with the increase in latitude; the ozone concentration in the north is higher and the ozone concentration in the south is lower in different seasons in western China, and it in autumn and summer is lower than that in spring and winter generally. The hour-by-hour change of ozone concentration shows that the ozone concentration in different seasons reaches a trough around 9–10 o’clock, and reaches a peak around 16–17 o’clock. When the RNN–CNN model is applied to predict the hourly change of ozone concentration within a day, it can achieve the best root-mean-squared error (18.13), mean absolute error (11.64), and index of agreement (0.973). The monitoring results of Lidar data at a certain site are compared and analyzed, and the results show that the fitness is the best between the predicted value of ozone concentration obtained by the RNN–CNN model and the actually measured value. This research provides the possibility for the intelligent prediction of atmospheric ozone concentration distribution and has reliable theoretical value and practical significance.

Summer and winter campaigns for the chemical compositions and sources of nonmethane hydrocarbons (NMHCs) and oxygenated volatile organic compounds (OVOCs) were conducted in Xi’an. Data from 57 photochemical assessment monitoring stations for NMHCs and 20 OVOC species were analyzed. Significant seasonal differences were noted for total VOC (TVOC, NMHCs and OVOCs) concentrations and compositions. The campaign-average TVOC concentrations in winter (85.3 ± 60.6 ppbv) were almost twice those in summer (47.2 ± 31.6 ppbv). Alkanes and OVOCs were the most abundant category in winter and summer, respectively. NMHCs, but not OVOCs, had significantly higher levels on weekends than on weekdays. Total ozone formation potential was higher in summer than in winter (by 50%) because of the high concentrations of alkenes (particularly isoprene), high temperature, and high solar radiation levels in summer. The Hybrid Environmental Receptor Model (HERM) was used to conduct source apportionment for atmospheric TVOCs in winter and summer, with excellent accuracy. HERM demonstrated its suitability in a situation where only partial source profile data were available. The HERM results indicated significantly different seasonal source contributions to TVOCs in Xi’an. In particular, coal and biomass burning had contributions greater than half in winter (53.4%), whereas traffic sources were prevalent in summer (53.1%). This study’s results highlight the need for targeted and adjustable VOC control measures that account for seasonal differences in Xi’an; such measures should target not only the severe problem with VOC pollution but also the problem of consequent secondary pollution (e.g., from ozone and secondary organic aerosols).

The review is based on the results of the operation of the total ozone (TO) monitoring over the CIS and Baltic countries that functions in the operational mode at the Central Aerological Observatory (CAO). The monitoring system uses data from the national network equipped with M-124 filter ozonometers, which is under the methodological supervision of the Main Geophysical Observatory. The quality of the functioning of the entire system is operationally controlled at CAO by the comparison with the OMI satellite equipment observations (NASA, USA). Basic TO observation data are generalized for each month of the second quarter of 2020 and for the second quarter. Data of routine observations of surface ozone values in the Moscow region are also considered.

The present study endeavors to explore the association between total column ozone (TCO) and surface temperature (ST) over Kolkata, India, during September–November through time series approach. A spectral analysis approach is adopted to investigate the existence of any common cycle in TCO and ST time series. The spectra have been computed, and it has been observed that there exist common spectra of period 24 in both the time series explored in daily scale. The existence of common spectra among TOC and ST during the transition period from monsoon to post-monsoon has been interpreted as a proof of the similarity in fluctuation pattern of TCO and ST. Details of the dependence of the variability of TCO on ST have been discussed.

The results of microwave radiometry studies of the ozone-content dynamics in the middle atmosphere above Peterhof during stratospheric warmings of two winters, 2015–2016 and 2016–2017, are presented. Ground-based observations employed mobile microwave ozone-measuring instrument (operating frequency is 110.8 GHz). The vertical ozone distribution in the altitude range of 22–60 km is estimated. The results are compared to satellite-borne data on the total ozone content, to vertical profiles of the ozone and temperature in the middle atmosphere, and to data from an ozone-measuring sounder. In the middle atmosphere above Peterhof, there have been significant variations (by several times) in the ozone content at heights of 40–60 km due to minor stratospheric warming.

© 2020, Geographical Institute "Jovan Cviji" of the Serbian Academy of Sciences and Arts. All rights reserved. Solar ultraviolet (UV) radiation is a significant health hazard in the warm part of the year. In order to assess the level of hazard and the effects of UV radiation on the living world, long-term measured or estimated data are needed. In Novi Sad, the measurement of UV radiation has been performed since 2003, while ozone measurements have been made since 2007. However, those data sets are too short for assessing long-term biological effects. Therefore, several techniques for reconstruction of UV radiation doses have been developed. Reconstruction techniques are based on using available ground-based measurements of the meteorological data and satellite measurements of the total ozone column. It is shown that techniques that use ozone data show better performance than those that use only ground-based meteorological measurements. However, the difference between the performances of the methods is smaller when it comes to the monthly values, indicating that the techniques which use only ground-based meteorological measurements are roughly as good as the ozone-based techniques for assessing long-term changes in the surface UV radiation. The statistically significant increasing long term-trend of annual mean erythemal UV doses (ERY) and the decreasing trend in the total ozone column in Novi Sad since 1981 have been noticed. An increase in ERY has been noticed in all the seasons except in autumn and it is the highest in winter. The analysis showed that the increase in the ERY in the period 1981–1996 was mainly caused by the total ozone column, while the increase after 1996 is largely caused by cloudiness.

Previous research on atmospheric chemistry in the forest environment has shown that the total reactivity by biogenic volatile organic compound (BVOC) emission is not well considered in for-est chemistry models. One possible explanation for this discrepancy is the unawareness and ne-glect of reactive biogenic emission that have eluded common monitoring methods. This ques-tion motivated the development of a total ozone reactivity monitor (TORM) for the direct de-termination of the reactivity of foliage emissions. Emissions samples drawn from a vegetation branch enclosure experiment are mixed with a known and controlled amount of ozone (e.g. re-sulting in 100 ppb of ozone) and directed through a temperature-controlled glass flow reactor to allow reactive biogenic emissions to react with ozone during the approximately 2-minute residence time in the reactor. The ozone reactivity is determined from the difference in the ozone mole fraction before and after the reaction vessel. An inherent challenge of the experi-ment is the influence of changing water vapor in the sample air on the ozone signal. A com-mercial UV absorption ozone monitor was modified to directly determine the ozone differential with one instrument and sample air was drawn through Nafion dryer membrane tubing. These two modifications significantly reduced errors associated with the determination of the reacted ozone compared to determining the difference from two individual measurements and errors from interferences from water vapor, resulting in a much improved and sensitive determina-tion of the ozone reactivity. This paper provides a detailed description of the measurement de-sign, the instrument apparatus, and its characterization. Examples and results from field de-ployments demonstrate the applicability and usefulness of the TORM.

The occurrence of the tropospheric ozone depletion events (ODEs) in the Antarctic can be influenced by the change in Total Ozone Column (TOC). In this study, we combined the observational data obtained from ground observation stations with two numerical models (TUV and KINAL), to figure out the relationship between the TOC change and the occurrence of ODEs in the Antarctic. A sensitivity analysis was also performed on the change in ozone and major bromine species (BrO, HOBr and HBr) to find out key photolysis reactions determining the impact on the occurrence of tropospheric ODEs brought by the change in TOC. From the analysis of the observational data and the numerical results, we suggested that the occurrence frequency of ODEs in the Antarctic seems negatively correlated with the variation of TOC. Moreover, major ODE accelerating reactions (i.e. photolysis of ozone, H2O2 and HCHO) and decelerating reactions (i.e. photolysis of BrO and HOBr), which heavily control the start of ODEs, were also identified. It was found that when TOC varies, the major ODE accelerating reactions speed up significantly, while major ODE decelerating reactions are only slightly affected, thus leading to the negative dependence of the ODE occurrence on the change in TOC.

Discrete wavelength radiance measurements from the Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) allows derivation of global synoptic maps of total and tropospheric ozone columns every hour during Northern Hemisphere (NH) Summer or 2 hours during Northern Hemisphere winter. In this study, we present version 3 retrieval of Earth Polychromatic Imaging Camera ozone that covers the period from June 2015 to the present with improved geolocation, calibration, and algorithmic updates. The accuracy of total and tropospheric ozone measurements from EPIC have been evaluated using correlative satellite and ground-based total and tropospheric ozone measurements at time scales from daily averages to monthly means. The comparisons show good agreement with increased differences at high latitudes. The agreement improves if we only accept retrievals derived from the EPIC 317 nm triplet and limit solar zenith and satellite looking angles to 70°. With such filtering in place, the comparisons of EPIC total column ozone retrievals with correlative satellite and ground-based data show mean differences within ±5-7 Dobson Units (or 1.5–2.5%). The biases with other satellite instruments tend to be mostly negative in the Southern Hemisphere while there are no clear latitudinal patterns in ground-based comparisons. Evaluation of the EPIC ozone time series at different ground-based stations with the correlative ground-based and satellite instruments and ozonesondes demonstrated good consistency in capturing ozone variations at daily, weekly and monthly scales with a persistently high correlation (r2 > 0.9) for total and tropospheric columns. We examined EPIC tropospheric ozone columns by comparing with ozonesondes at 12 stations and found that differences in tropospheric column ozone are within ±2.5 DU (or ∼±10%) after removing a constant 3 DU offset at all stations between EPIC and sondes. The analysis of the time series of zonally averaged EPIC tropospheric ozone revealed a statistically significant drop of ∼2–4 DU (∼5–10%) over the entire NH in spring and summer of 2020. This drop in tropospheric ozone is partially related to the unprecedented Arctic stratospheric ozone losses in winter-spring 2019/2020 and reductions in ozone precursor pollutants due to the COVID-19 pandemic.

Sixteen years (July 2003–July 2019) of ground-based measurements of total ozone in the urban environment of Athens, Greece, are analyzed in this work. Measurements were acquired with a single Brewer monochromator operating on the roof of the Biomedical Research Foundation of the Academy of Athens since July 2003. We estimate a 16-year climatological mean of total ozone in Athens of about 322 DU, with no significant change since 2003. Ozone data from the Brewer spectrophotometer were compared with TOMS, OMI, and GOME-2A satellite retrievals. The results reveal excellent correlations between the ground-based and satellite ozone measurements greater than 0.9. The variability of total ozone over Athens related to the seasonal cycle, the quasi biennial oscillation (QBO), the El Nino Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), the 11-year solar cycle, and tropopause pressure variability is presented.

The ozone concentration in the atmosphere has been recovering with the reduction in atmospheric ozone-depleting substances (ODS). However, ODS remain in the atmosphere for long periods, slowing recovery. Furthermore, greenhouse gas-induced climate change complicates ozone recovery. East Asia is a significant contributor to global climate change due to the increase in industrialization and the presence of complex climate conditions. We investigated ozone variations in East Asia using total column ozone data based on satellite and ground observations and compared the results and trends derived from a multi-linear regression (MLR) model. We found that the MLR model has relatively poor explanatory power for recent extraterrestrial and dynamical proxies, but the uncertainty can be reduced using monthly data and atmospheric proxies. The ozone trend in East Asia had the greatest increase in the vicinity of the Korean Peninsula and Manchuria from 1997 to 2017 (~1% per decade). Similarly, the trend derived from Brewer spectrophotometer data was 1.02 ± 1.45% per decade in Pohang and 1.27 ± 0.85% per decade in Seoul. When the analysis period was extended to 2020, the impact of atmospheric variability was greater, suggesting that recent climate change can increasingly contribute to total ozone variability.

The review is based on the results of the operation of the system of total ozone (TO) monitoring over Russia and neighboring territories that functions in the operational mode at the Ceniral Aerological Observatory (CAO). The monitoring system uses data from the national network equipped with M-124 filter ozonometers being under the methodological supervision of the Main Geophysical Observatory. The quality of the entire system functioning is operationally controlled by the comparison with the observations obtained from the OMI satellite equipment (NASA, USA). Basic TO observation data are generalized for each month of the second quarter of 2019 and for the second quarter. Data of routine observations of surface ozone values in the Moscow region and Crimea are also considered.

In this work, the impact of various factors on the total ozone column and erythemal UV radiation (Qery) in the territory of Northern Eurasia for the period from 1979 to 2059 based on the calculations of the chemical-climate model INM-RHSU is analyzed. The sensitivity of ozone recovery to the setting of different input data on sea surface temperature (SST) is estimated. Depending on the SST datasets, there are significant differences in ozone trends. A possible mechanism that explains the reasons for these differences is examined. The numerical experiment with the only change in ozone depleting substances according to Montreal protocol showed the ozone recovery and, as a result, Qery reduction, but this recovery is not linear. During the 2016-2020 period we estimated the 2-5% increase in Qery values relative to the baseline period (1979-1983) with about 6% maximum over Russian polar region. During the 2035-2039 period the Qery change against 1979-1983 period is about zero, during the 2055-2059 period we obtained the decrease of about 4-6% over Northern Asia and 6-8% over Northern Europe These changes corresponded to the noticeable boundary location shift of UV resources, which determine UV radiation impact on human health. The most significant changes will be observed in spring and summer: the UV deficiency zone will be expanded in the north and the UV excess zone over northern seas will be reduced in the south.

The review is compiled of the results of the total ozone (TO) monitoring in the CIS and Baltic countries that functions in the operational mode at the Central Aerological Observatory (CAO). The monitoring system uses data from the national net work equipped with M-124 filter ozonometers op er at -ing under the methodological supervision of the Main Geophysical Observatory. The quality of the functioning of the entire system is operation ally con trolled in CAO by the comparison with the observations obtained from the OMI satellite equipment (NASA, USA). Basic TO observation data are generalized for each month of the first quarter of 2019 and for the first quarter. Data of routine observations of surface ozone values in the Moscow region and Crimea are also considered.

A continuous online observation of ozone and its precursors (NOx, VOCs) was carried out in central urban Wuhan from September 2016 to August 2017. The concentration levels of ozone, NOx, VOCs and their variations in urban Wuhan were analyzed, as well as effects of VOCs on ozone photochemical generation and the main controlling factors for ozone production. During the observation period, the average concentrations of ozone and NOx in Wuhan was 22.63 and 30.14 ppbv, respectively, and the average concentration of VOCs was 32.61 ppbv (42.3% alkanes, 13.0% alkenes, 10.0% aromatics, 7.3% acetylene, 9.9% OVOCs, and 10.5% halohydrocarbons). Ozone concentration was higher in spring and summer as compared with autumn and winter, wheras VOCs and NOx concentratios were lower in spring and summer but higher in autumn and winter. Aromatics and alkenes, two of VOCs species, showed the highest contributions to ozone formation potential in Wuhan (35.7% alkenes, 35.4 aromatics, 17.5% alkanes, 8.6% OVOCs, 1.6% halogenated hydrocarbons, and 1.4% acetylene). Among all VOCs species, those with the highest contribution were ethylene, m-xylene, toluene, propylene and o-xylene. The contribution of these five compounds to the total ozone formation potential concentration was 43.90%. Ozone-controlling factors in Wuhan changed within one day; during the early morning hours (6:00–9:00), VOCs/NOx was low, and ozone generation followed a VOCs-limited regime. However, during the peak time of ozone concentration (12:00–16:00), the ratio of VOCs/NOx was relatively high, suggesting that ozone generation followed a NOx-limited regime.

The global ozone layer has been continuously depleted in the last few decades due to the anthropogenic emissions of the ozone depleting substances (ODSs). This has created major concern for the ecosystem as well as mankind. This points to the need to examine the influence of each individual ODS in order to estimate how this burden can change in the future. To that end, we have analysed 52 years (1965–2017) data of the ozone depleting substances using the Box-Jenkins model, and have predicted the future trend of the ODSs until the year 2030. On the basis of the relationship between the trend in variations of the ozone depleting substances and the total ozone column, we have established that how much of the recent ozone increment is attributable to the concentration of the ozone depleting substances. By using the above mentioned model, we have estimated that the present atmospheric abundance of chlorine and bromine is about 3325 and 14.3 parts per trillion (ppt) respectively and have calculated that the atmospheric abundance of these substances will reduce to values of 3217 ppt (∼3.2%) and 13.1 ppt (∼8.3%) respectively. We have also inferred that if the decreasing trend of ODSs continues with the same rate in the coming decades, the ozone column will increase by 9–10% and the ozone level will return to its pre-1980 level by the year 2030.

Dobson and Brewer spectrophotometers are the primary, standard instruments for ground-based ozone measurements under the World Meteorological Organization's (WMO) Global Atmosphere Watch program. The accuracy of the data retrieval for both instruments depends on a knowledge of the ozone absorption coefficients and some assumptions underlying the data analysis. Instrumental stray light causes nonlinearity in the response of both the Brewer and Dobson to ozone at large ozone slant paths. In addition, it affects the effective ozone absorption coefficients and extraterrestrial constants that are both instrument-dependent. This effect has not been taken into account in the calculation of ozone absorption coefficients that are currently recommended by WMO for the Dobson network. The ozone absorption coefficients are calculated for each Brewer instrument individually, but in the current procedure the effect of stray light is not considered. This study documents the error caused by the effect of stray light in the Brewer and Dobson total ozone measurements using a physical model for each instrument. For the first time, new ozone absorption coefficients are calculated for the Brewer and Dobson instruments, taking into account the stray light effect. The analyses show that the differences detected between the total ozone amounts deduced from Dobson AD and CD pair wavelengths are related to the level of stray light within the instrument. The discrepancy introduced by the assumption of a fixed height for the ozone layer for ozone measurements at high latitude sites is also evaluated. The ozone data collected by two Dobson instruments during the period of December 2008 to December 2014 are compared with ozone data from a collocated double monochromator Brewer spectrophotometer (Mark III). The results illustrate the dependence of Dobson AD and CD pair measurements on stray light.

The variability of Arctic total ozone in the winter of 2015/2016 is studied using the data of the national network equipped with M-124 filter ozonometers and satellite monitoring. The first ozone mini-hole that emerged in the first half-year over the whole history of observations (developed at the end of January 2016) is analyzed. The reasons for the total ozone variability over Russia in the first quarter of 2016 are analyzed, and the comparison with the significant Arctic ozone anomalies in 1996/1997 and 2010/2011 is presented.

This study analyses the variations of aerosol optical depth, total column ozone and water vapour, measured by a Microtops-II (MICRO-processor based Total Ozone Portable Spectrometer) ozonometer/sunphotometer over a coastal station in southwest peninsular India, Kochi. Observations of ozone and aerosols are analysed for a period, May 2012 to May 2013. Satellite data sets available over the region are also analysed, and a comparison is made with the in situ data. Sunphotometer measured 1020 nm aerosol optical depth (AOD) shows a temporal variability with an increase in AOD during the summer (high value of 0.35 in May 2012) and fewer values near 0.2 during the winter and the post-monsoon seasons. Satellite observations also show a similar pattern of variability with high AOD during the summer. Water vapour is maximum (near 3.5 cm) during the pre-monsoon and the summer monsoon and minimum (below 2 cm in January 2013) during the winter. Ozone shows seasonal variability with a minimum concentration during the winter (230 Dobson Unit (DU) in January 2013) and maximum (280 DU in May 2012) during the summer. OMI (Ozone measuring Instrument) onboard Aura satellite overestimates the column ozone by 10 DU in comparison with the Microtops ozonometer. However, the sunphotometer and satellite observations show a similar pattern of temporal variability with a small difference in magnitude during certain months. The zonal ozone distribution shows a seasonal variability with a reverse gradient between the summer and the winter.

In the present study, 3-D chemical transport model, MOZART-4 (Model for Ozone and Related chemical Tracers-Version-4) has been used to study the seasonal and spatial distribution of surface ozone (O3) over India. To illustrate the capabilities of model, the simulations are compared with the ground-based observations. The model reproduces the principal features present in ground-based observations. However, model is unable to simulate very low concentration of O3 during monsoon months. The model simulations are used to quantify the contribution of background ozone and Indian anthropogenic emissions to the variability of surface O3. The spatial distribution of total O3 (TO) shows maximum over Indo-Gangetic plains (IGP) and Eastern India while minimum over southern Indian region. The seasonal cycle of TO vary from 34.2 ± 7.6 to 51.9 ± 4.9 ppbv over the Indian landmass region due to changes in its topography and ozone lifetime. Annual mean total background O3 (TBO) over India shows highest during spring (29.3 ± 5.0 ppbv) and lowest during monsoon (19.6 ± 3.4 ppbv). Both Natural background O3 (NBO) and pollution background O3 (PBO) shows a minimum in summer which are essentially following the seasonal changes of total ozone. Significant variation of India pollution O3 (IPO) is found over India and the spatial variation of IPO follows the spatial variation of TO as well as spatial variation of emission of ozone precursors.

Episodes of extremely low ozone columns were observed over the territory of Russia in the Arctic winter of 2015/2016 and the beginning of spring 2016. We compare total ozone columns (TOC) obtained using different remote sensing techniques (satellite and ground-based observations) and results of numerical modelling over the territory of the Urals and Siberia for the above period. We demonstrate that the provided monitoring systems (including new Russian Fourier- spectrometer IKFS-2) and modern 3-dimensional models are able to capture the observed TOC anomalies. However, the results of observations and modelling show discrepancies of up to 20–30 % in TOC measurements. Analysis of the role of chemical and dynamical processes demonstrates that it is unlikely that observed short-term TOC variability may be a result of local photochemical destruction initiated by heterogeneous halogen activation on particles of polar stratospheric clouds that formed under low temperatures in the mid-winter.

In this paper we investigate response of the total ozone column to energetic electron precipitation (EEP) observed by bremsstrahlung effect. The list of EEP events was prepared by members of the balloon experiments of the Lebedev Physical Institute. Here we used superposed epoch analysis and the days with EEP events are registered during winter (November–February) and summer (June–August) months from 1970 to 2012 were chosen as key dates. This period corresponds approximately to three solar cycles. Data of the total ozone column were collected by single coherent total ozone dataset, called the Multi Sensor Reanalysis (MSR). A long series of data of the total ozone column is allowed us to study the response of ozone content to 90 winter and 103 summer EEP events. The obtained ozone sensitivity to the events of energetic electron precipitation is clearly pronounced during local winters in the high latitudes of the Northern and Southern Hemispheres (60–80 NH and 60–80 SH). In the high latitudes of the Northern Hemisphere, during winter months, the total ozone content can be reduced by up to 10 DU after energetic electron precipitation with minimum observed on the first day after EEP events. Response of the total ozone, over high latitudes of the Northern Hemisphere, to EEP events can be opposite during summer months.

The ground-based ozone observation instrument, Brewer spectrophotometer (Brewer), was used to evaluate the quality of the total ozone column (TOC) produced by multiple polar-orbit satellite measurements at three stations in Antarctica (King Sejong, Jang Bogo, and Zhongshan stations). While all satellite TOCs showed high correlations with Brewer TOCs (R = ~0.8 to 0.9), there are some TOC differences among satellite data in austral spring, which is mainly attributed to the bias of Atmospheric Infrared Sounder (AIRS) TOC. The quality of satellite TOCs is consistent between Level 2 and 3 data, implying that “which satellite TOC is used” can induce larger uncertainty than “which spatial resolution is used” for the investigation of the Antarctic TOC pattern. Additionally, the quality of satellite TOC is regionally different (e.g., OMI TOC is a little higher at the King Sejong station, but lower at the Zhongshan station than the Brewer TOC). Thus, it seems necessary to consider the difference of multiple satellite data for better assessing the spatiotemporal pattern of Antarctic TOC.

Weather forecast based on extrapolation methods is gathering a lot of attention due to the advance of artificial intelligence. Recent works on deep neural networks (CNN, RNN, LSTM, etc.) are enabling the development of spatiotemporal prediction models based on the analysis of historical time-series, images, and satellite data. In this paper, we focus on the use of deep learning for the forecast of stratospheric Ozone ( $$O_3$$ ), especially in the cases of exchanges between the polar vortex and mid-latitudes known as Ozone Secondary Events (OSE). Secondary effects of the Antarctic Ozone Hole are regularly observed above populated zones on South America, south of Africa, and New Zealand, resulting in abrupt reductions in the total ozone column of more than 10% and a consequent increase in UV radiation in densely populated areas. We study different OSE events from the literature, comparing real data with predictions from our model. We obtained interesting results and insights that may lead to accurate and fast prediction models to forecast stratospheric Ozone and the occurrence of OSE.

The total ozone column (TOC) is retrieved using multiple optical satellite instrumentation (including TOMS, OMI, TROPOMI, GOME, GOME-2, and SCIAMACHY, to name a few). The spatial resolution of total ozone satellite measurements is quite low (e.g., 7x3.5km for TROPOMI, 13x24km for OMI, and 30x60km for SCIAMACHY). In some cases (say, close to the ozone hole boundary) it is of importance to have information on the total ozone at a higher spatial resolution. In this work we propose the use of multiple optical instruments performing the measurements in the ozone Chappuis ozone bands (400-650nm) for the total ozone column determination. This makes it possible to extend the number of instruments, which can be used for the total ozone determination (say, also using current/historic measurements by MODIS/Aqua&Terra, S-GLI/SCOM-C, VIIRS/Suomi-NPP, MSI/S-2, OLCI/S-3, MERIS/ENVISAT). In particular, MERIS and SCIAMACHY have been operated from the same satellite platform and had similar swaths (960km for SCIAMACHY and 1150km for MERIS). This means the method of total ozone retrieval based on combination of SCIAMACHY (30x60km) and MERIS (0.3x0.3km) observations over highly reflective ground (say, in Antarctica, where the ozone hole is located) is of value. The total ozone retrievals using Chappuis ozone bands is based on the fact that the top-of-atmosphere reflectance observed over a highly reflective ground (say, snow) has a minimum in the visible located around 600nm. This feature is due to due to the absorption of light by the atmospheric ozone (Gorshelev et al., 2014). The contribution of both ground and atmospheric light scattering to the top-of-atmosphere (TOA) does not have extrema in the vicinity of 600nm. Therefore, there is a possibility to remove both atmospheric and ground light scattering effects to the TOA reflectance over highly reflective underlying surface and derive the atmospheric transmittance due to the ozone absorption effects, which can be used for the TOC determination. Such a method has been explored using MERIS/ENVISAT (Jolivet et al., 2016) and OLCI/S-3 (Kokhanovsky et al., 2020) in the past. This paper is aimed at further improvement of the technique as applied to OLCI/S-3A,B. We have performed intercomparisons of OLCI TOC retrievals with TOC derived from ground and other satellite (e.g., OMI, TROPOMI, GOME-2) measurements. The TOC retrievals using OLCI have been performed over entire Antarctica allowing the generation of TOC at various spatial resolutions including standard 1x1 degree resolution.Gorshelev, V., et al., 2014: High spectral resolution ozone absorption cross-sections – Part 1: Measurements, data analysis and comparison with previous measurements around 293 K, Atmos. Meas. Tech., 7, 609–624, https://doi.org/10.5194/amt-7-609-2014.Jolivet D., et al., 2016: TORMS : total ozone retrieval from MERIS in view of application to Sentinel-3, Living Planet Symposium, Proceedings of the conference held 9-13 May 2016 in Prague, Czech Republic. Edited by L. Ouwehand. ESA-SP Volume 740, ISBN: 978-92-9221-305-3, p.358Kokhanovsky, A. A., et al., 2020: Retrieval of total ozone over Antarctica using Sentinel -3 Ocean and Land Colour Instrument, JQSRT, 2020, 251, https://doi.org/10.1016/j.jqsrt.2020.107045.

10 pags., 4 figs., Many Chemistry-Climate Models (CCMs) include a simplified treatment of brominated very short-lived (VSL) species by assuming CHBr as a surrogate for VSL. However, neglecting a comprehensive treatment of VSL in CCMs may yield an unrealistic representation of the associated impacts. Here, we use the Community Atmospheric Model with Chemistry (CAM-Chem) CCM to quantify the tropospheric and stratospheric changes between various VSL chemical approaches with increasing degrees of complexity (i.e., surrogate, explicit, and full). Our CAM-Chem results highlight the improved accuracy achieved by considering a detailed treatment of VSL photochemistry, including sea-salt aerosol dehalogenation and heterogeneous recycling on ice-crystals. Differences between the full and surrogate schemes maximize in the lowermost stratosphere and midlatitude free troposphere, resulting in a latitudinally dependent reduction of ∼1–7 DU in total ozone column and a ∼5%–15% decrease of the OH/HO ratio. We encourage all CCMs to include a complete chemical treatment of VSL in the troposphere and stratosphere., This study has been funded by the European Union's Horizon 2020 Re-search and Innovation program (Project ‘ERC-2016-COG 726349 CLIMAHAL’), and supported by the Consejo Superior de Investigaciones Científicas of Spain. Computing resources and support are provided by the Computational and Information System Laboratory (CISL,2017). R. P. Fernandez would like to thank financial support from CONICET, ANPCyT (PICT 2015-0714), UNCuyo (SeCTyP M032/3853) and UTN (PID 4920-194/2018). NCAR is sponsored by NSF under grant number 1852977. R. J. Salawitch appreciates support from the NASA (grant ACMP 80NSSC19K0983). The authors thank two anonymous reviewers for their constructive comments

An accurate characterization of spatial-temporal emission patterns and speciation of volatile organic compounds (VOCs) for multiple chemical mechanisms is important to improving the air quality ensemble modeling. In this study, we developed a 2017-based high-resolution (3 km × 3 km) model-ready emission inventory for Guangdong Province (GD) by updating estimation methods, emission factors, activity data, and allocation profiles. In particular, a full-localized speciation profile dataset mapped to five chemical mechanisms was developed to promote the determination of VOC speciation, and two dynamic approaches based on big data were used to improve the estimation of ship emissions and open fire biomass burning (OFBB). Compared with previous emissions, more VOC emissions were classified as oxygenated volatile organic compound (OVOC) species, and their contributions to the total ozone formation potential (OFP) in the Pearl River Delta (PRD) region increased by 17%. Formaldehyde became the largest OFP species in GD, accounting for 11.6% of the total OFP, indicating that the model-ready emission inventory developed in this study is more reactive. The high spatial-temporal variability of ship sources and OFBB, which were previously underestimated, was also captured by using big data. Ship emissions during typhoon days and holidays decreased by 23–55%. 95% of OFBB emissions were concentrated in 9% of the GD area and 31% of the days in 2017, demonstrating their strong spatial-temporal variability. In addition, this study revealed that GD emissions have changed rapidly in recent years due to the leap-forward control measures implemented, and thus, they needed to be updated regularly. All of these updates led to a 5–17% decrease in the emission uncertainty for most pollutants. The results of this study provide a reference for how to reduce uncertainties in developing model-ready emission inventories.

Characteristics of atmospheric VOCs (volatile organic compounds) have been extensively studied in megacities in China, however, they are scarcely investigated in medium/small-sized cities in North China Plain (NCP). A comprehensive research on possible sources of VOCs was conducted in a medium-sized city of NCP, from May to September 2019. A total of 143 canister samples of 8 sites in Xuchang city were collected, and 57 VOC species were detected. The average VOC concentrations were 42.6 ± 31.6 μg/m3, with 53.7 ± 31.0 μg/m3 and 32.1 ± 27. 8 μg/m3, in the morning and afternoon, respectively. Alkenes and aromatics contributed 80% of the total ozone formation potential (OFP). Aromatics accounted for more than 95% of secondary organic aerosol potential (SOAP). VOCs were dominated by the local emission with significant transport from the southeast direction. PMF analysis extracted 6 sources, which were combustion (33.1%), LPG usage (19.3%), vehicular exhaust & fuel evaporation (15.8%), solvent usage (15.2%), industrial (9.11%) and biogenic (7.51%), respectively and they contributed 33.4%, 17.6%, 12.9%, 18.6%, 9.28% and 8.22% to the OFP, respectively. Combustion and LPG usage were the dominant VOC sources; and combustion, solvent usage and LPG usage were the main sources of OFP in Xuchang city, which were different to megacities in China with a high contribution from vehicular exhaust, solvent usage and industry, suggesting specific control strategies on VOCs need to be implemented in medium-sized city such as Xuchang city.

The success of the Montreal Protocol in curbing increases in harmful solar ultraviolet (UV) radiation at the Earth&rsquo, s surface has recently been demonstrated. This study also provided evidence that the UV Index (UVI) measured by SUV-100 spectroradiometers at three Antarctic sites (South Pole, Arrival Heights, and Palmer Station) is now decreasing. For example, a significant (95% confidence level) downward trend of &minus, 5.5% per decade was reported at Arrival Heights for summer (December through February). However, it was also noted that these measurements are potentially affected by long-term drifts in calibrations of approximately 1% per decade. To address this issue, we have reviewed the chain of calibrations implemented at the three sites between 1996 and 2018 and applied corrections for changes in the scales of spectral irradiance (SoSI) that have occurred over this period (Method 1). This analysis resulted in an upward correction of UVI data measured after 2012 by 1.7% to 1.8%, plus smaller adjustments for several shorter periods. In addition, we have compared measurements during clear skies with model calculations to identify and correct anomalies in the measurements (Method 2). Corrections from both methods reduced decadal trends in UVI on average by 1.7% at the South Pole, 2.1% at Arrival Heights, and 1.6% at Palmer Station. Trends in UVI calculated from the corrected dataset are consistent with concomitant trends in ozone. The decadal trend in UVI calculated from the corrected dataset for summer at Arrival Heights is &minus, 3.3% and is significant at the 90% level. Analysis of spectral irradiance measurements at 340 nm suggests that this trend is partially caused by changes in sea ice cover adjacent to the station. For the South Pole, a significant (95% level) trend in UVI of &minus, 3.9% per decade was derived for January. This trend can partly be explained by a significant positive trend in total ozone of about 3% per decade, which was calculated from SUV-100 and Dobson measurements. Our study provides further evidence that UVIs are now decreasing in Antarctica during summer months. Reductions have not yet emerged during spring when the ozone hole leads to large UVI variability.

International audience; We analyze the 2019 sudden stratospheric warming event that occurred in the Southern Hemisphere through its impact on the Antarctic ozone. Using temperature, ozone, and nitric acid data from the Infrared Atmospheric Sounding Interferometer (IASI), our results show that the average increase in stratospheric temperature reached a maximum of 34.4° on September 20th in the [60‐90]°S latitude range when compared to the past three years. Dynamical parameters suggest a locally‐reversed and weakened zonal winds and a shift in the location of the polar jet vortex. This led to air masses mixing, to a reduced polar stratospheric clouds formation detected at a ground station, and as such to lower ozone and nitric acid depletion. 2019 total ozone columns for the months of September, October, and November, were on average higher by 29%, 28%, and 26% respectively when compared to the 11‐year average of the same months.

Combining information from several channels of the Norwegian Institute for Air Research (NILU-UV) irradiance meter, one may determine the total ozone column (TOC) amount. A NILU-UV instrument has been deployed and operated on two locations at Troll research station in Jutulsessen, Queen Maud Land, Antarctica, for several years. The method used to determine the TOC amount is presented, and the derived TOC values are compared with those obtained from the Ozone Monitoring Instrument (OMI) located on NASA’s AURA satellite. The findings show that the NILU-UV TOC amounts correlate well with the results of the OMI and that the NILU-UV instruments are suitable for monitoring the long-term change and development of the ozone hole. Because of the large footprint of OMI, NILU-UV is a more suitable instrument for local measurements. © 2020 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved

A regional climate change, as a long-term repeated weather regime typical for a specific area, has become one of the main themes in Climate Change (CC) research. Forecasting the possible climate changes requires knowledge of the variations of natural and anthropogenic climate-forming factors, understanding of the mechanisms that determine the response of the Earth’s climate system to these impacts. One of the factors influencing the regional climate is the total ozone content in the atmosphere. The aim of this article is to establish a correlation links between the total ozone content and the short-term regional climatic events. Presented analysis is based on data from orbital observations of the movement of ozone anomalies, data from different databases and researches of the National Ozone Monitoring Research and Education Center.

Producción Científica, Ultraviolet (UV) radiation plays a key role in different planetary mechanisms, thus necessitating a worldwide analysis of this solar spectrum interval. This study offers a worldwide and long-term analysis of ozone radiative forcing (ORF) in the UV-B range between 1979 and 2014. The method uses monthly total ozone column (TOC) values obtained from the ERA-Interim reanalysis data collection and radiative transfer simulations. A global mean ORF of 0.011 Wm−2 is obtained, with marked differences between mid-latitude and tropical areas. The mid-latitude belts in the Northern and Southern Hemispheres exhibit the following statistically significant ORF trends between 1982 and 2014 with respect to pre-1980 values: 0.007 Wm−2 per decade in the 60–45°S belt and around 0.004 Wm−2 per decade in the 45–30°S and 45–60°N belts. The increase observed in the net UV-B radiation levels at the troposphere might have relevant photochemical effects that impact climate change., Ministerio de Ciencia, Innovación y Universidades (grant RTI2018-097864-B-I00)

After successful implementation of the Montreal Protocol, total ozone column (TOC) has considerably increased since the mid 1990s. However, the recovery is weak and statistically non-significant particularly at low-latitudes as the healing encounters many obstacles during the process. Decline trend of TOC over high-altitude (3000 m–5000 m amls) entire region in Ladakh (32N - 35N, 77E - 80E), India located in the western trans-Himalayan region which extends upto Tibetan Plateau (TP) in mid-latitude, is approaching in an alarming rate of ∼ -1.30 DU/year from the last few decades. The present work intends to examine whether the ozone recovery is already started or yet to start over the region using TOMS-OMI and SBUV-merged data during 1970–2017. During the TOC depletion, the estimated trends are deepening and statistically significant with −1.27 to −1.32 DU per year over the region. However, recovery of TOC has noticed over the region in the recent years and healing is still slow and statistically non-significant with 0.14–0.23 DU per year. Such non-significant trends are associated with variabilities from natural cycles, such as Brewer-Dobson circulation (BDC), Quasi-Biennial Oscillation (QBO), 11 year solar cycle, etc., and these effects can be removed using multiple linear regression (MLR) model. Solar maxima during the last four cycles (21–24) are nearly followed by the TOC maxima. Upward transport of air by BDC can move ozone poor air into the lower stratosphere as noticed by elevated vertical pressure velocity which may offset the ozone recovery over the region. With relevant to the TOC recovery, the surface temperature over Ladakh region is warming at a rate of 0.3–0.4 K per year during 1980–2016. Further, the study noticed recovery of TOC at both the hemispheres with maximum of 0.23–0.50 DU per year at high-latitudes (45–60) using the MRL model. However, results of the TOC recovery at low-latitudes (15–30) in both the hemispheres are weak with 0.03–0.10 DU per year.

We present the annual variations in the total ozone (TO) content over Tomsk in the period of 1994-2017, obtained using М-124 ozonometer, and in the integrated aerosol backscattering coefficient in the period of 2000-2016. Their analysis made it possible to formulate the notion of seasonal behavior of these constituents and to compare their variations with the processes in “charging”/“discharging” capacitor.

Volatile organic compounds (VOCs) are the main precursors of tropospheric ozone and secondary aerosol generation, posing a threat to human health and affecting the environmental climate. A large quantity of VOCs can be produced in the initial decomposition stage of municipal solid waste (MSW). In this study, the atmosphere in an MSW transfer station was monitored for one year. The emission characteristics of VOCs in different seasons and working hours were analyzed, and the ozone-formation potential of VOCs was calculated through the maximum incremental reaction method, and health risks posed by the VOCs in the MSW transfer station were assessed. The results showed that the highest concentration of VOCs appeared in spring and summer, accounting for 70.6% and 26.6% of total VOCs (TVOCs) in peak working periods, respectively. Oxygenated compounds and terpenes contributed most to ozone formation, accounting for 41.0% and 50.6% of total ozone formation, respectively. The carcinogenic risks were above the safe threshold, labeled "probable risks". Tetrachloroethylene and 1,2-dichloroethane were the main contributors to carcinogenic risks. The mean non-carcinogenic risks were within the safe threshold in the MSW transfer station. From the perspective of protecting human health and ecological environmental safety, VOC control needs to be further strengthened in the transfer station.

China is facing a severe ozone problem, but the origin of its ozone remains unclear. Here we use a GEOS-Chem based global–regional two-way coupled model system to quantify the individual contributions of eight emission source regions worldwide to springtime ozone in 2008 over China. The model reproduces the observed ozone from 31 ground sites and various aircraft and ozonesonde measurements in China and nearby countries, with a mean bias of 10 %–15 % both near the surface and in the troposphere. We then combine zero-out simulations, tagged ozone simulations, and a linear weighting approach to account for the effect of nonlinear chemistry on ozone source attribution. We find considerable contributions of total foreign anthropogenic emissions to surface ozone over China (2–11 ppb). For ozone of anthropogenic origin averaged over China, foreign regions together contribute 40 %–60 % below the height of 2 km and 85 % in the upper troposphere. For total ozone contributed by foreign anthropogenic emissions over China at various heights, the portion of transboundary ozone produced within foreign emission source regions is less than 50 %, with the rest produced by precursors transported out of those source regions. Japan and Korea contribute 0.6–2.1 ppb of surface ozone over the east coastal regions. Southeast Asia contributes 1–5 ppb over much of southern China and South Asia contributes up to 5–10 ppb of surface ozone over the border of southwestern China; and their contributions increase with height due to strong upwelling over the source regions. The European contribution reaches 2.1–3.0 ppb for surface ozone over the northern border of China and 1.5 ppb in the lower troposphere averaged over China. North America contributes 0.9–2.7 ppb of surface ozone over most of China (1.5–2.1 ppb over the North China Plain), with a China average at 1.5–2.5 ppb at different heights below 8 km, due to its large anthropogenic emissions and the transport-favorable midlatitude westerly wind. In addition to domestic emission control, global emission reduction is critical for China's ozone mitigation.

This work presents an assessment of the global and hemispheric total ozone mass and its interannual variations, using the total number of daily satellite measurements from the Total Ozone Mapping Spectrometer (TOMS) version 8 and Ozone Monitoring Instrument (OMI) level 3. The mean total ozone mass was 3.1283 ± 0.1337 × 10 12 kg from November 1978 to November 1979, and 2.9979 ± 0.0917 × 10 12 kg from November 2004 to November 2005. The difference (1.3033 ± 0.3221 × 10 11 kg) represents a 4.2 ± 0.3% decrease in 26 yrs (1.615 ± 0.113% per decade), around 3% corresponding to the Northern Hemisphere and 5% corresponding to the Southern Hemisphere; 1.2 and 2.0% per decade, respectively. Differences in total ozone mass trends between Northern and Southern hemispheres indicate a change in geographic ozone distribution in the Southern Hemisphere. A linear fit between November 1978 and November 1991 shows a global ozone decrease of 4.72 × 10 9 kg per year, representing a loss of 1.5% per decade. Additionally, we found a net interannual variation of 16% of the total quantity existing during the equinoxes, when the maximum annual total ozone mass is reached.

The instrumental temperature corrections to be applied to the ozone measurements by the Brewer spectrophotometers are derived from the irradiance measurements of internal halogen lamps in the instruments. These characterizations of the Brewer spectrophotometers can be carried out within a thermal chamber, varying the temperature from -5 to +45ºC, or during field measurements, making use of the natural change in ambient temperature. However, the internal light source used to determine the thermal sensitivity of the instrument could be affected in both methods by the temperature variations as well, which may affect the determination of the temperature coefficients. In order to validate the standard procedures for determining Brewer’s temperature coefficients, two independent experiments using both external light sources and the internal halogen lamps have been performed within the ATMOZ Project. The results clearly show that the traditional methodology based on the internal halogen lamps is not sensitive to the temperature-caused changes in the spectrum of the internal light source. The three methodologies yielded equivalents results, with differences in total ozone column below 0.08% for a mean diurnal temperature variation of 10ºC. This work has been supported by the European Metrology Research Programme (EMRP) within the joint research project ENV59 “Traceability for atmospheric total column ozone” (ATMOZ).

This study employs a mass balance technique-box model to calculate the biogenic isoprene emissions based on the ground-level measurements between October 2009 and September 2010 in Beijing. The annual magnitude, monthly variations and diurnal patterns of isoprene emissions are estimated. The annual emissions of isoprene were estimated to be 23.2Gg with an uncertainty of 120%. This falls within the range of previous emission inventories (EI; 3.8Gg to 36.3Gg between 1990 and 2010). Strong isoprene emissions were observed between May and September. The biggest difference was the isoprene emissions in May, with contributions of 23.3% to total annual emissions using box model estimates compared with 3.7% in EI. The diurnal profiles of isoprene emissions estimated in this study were generally similar to those in the EI, with the highest emissions occurring during mid-day (11:00-13:00). However, obvious differences were found for the growth rates and decreasing rates of isoprene emissions in the morning and afternoon respectively. Compared to anthropogenic volatile organic compounds (VOCs), the isoprene emissions contributed half (49.5%) of the total ozone formation potential (OFP) at 13:00 in August, which highlights the importance of isoprene in ozone formation. This study helps bound the isoprene emissions estimated by EI despite the inherent large uncertainty.

The review is based on the operation results of the system for total ozone (TO) monitoring in the CIS and Baltic countries functioning in the operational regime at the Central Aerological Observatory (CAO). The monitoring system uses data from the national network equipped with M-124 filter ozonometers being under the methodological supervision of the Main Geophysical Observatory. The quality of the entire system functioning is operationally controlled in CAO through the comparison with the observations obtained from the OMI satellite equipment (NASA, USA). Basic TO observation data are generalized for each month of the fourth quarter of 2017, for the whole fourth quarter, and for the whole year. The data of routine observations of surface ozone values in the Moscow region and Crimea are also considered.

The main objective of the study is development a method for forecasting the state of ozone above the Ukrainian Antarctic Akademik Vernadsky station since 1972 are presented in the article.The result of study of the state of ozone above Vernadsky station from 1972 is given in the article. An analogue to the state of ozone 2016/2017 is found using the similarity criteria from the observations archive of the station. The proposed model of the change in large-scale atmospheric circulation for the Southern Hemisphere is used to predict the state of the ozone over the Vernadsky station in the next decade. Main conclusion from this study is that in the next decade should expect an increase in the total ozone above the station.

In this research, the climatological characteristics of total column ozone (ToZ) over Irene, South Africa (25.5o S, 28.1o E), are studied using both ground-based and satellite observations. Satellite data from the Total Ozone Mapping Spectrometer (TOMS) from November 1978 to May 1993; the Global Ozone Monitoring Experiment-1 (GOME-1) from August 1995 to June 2003; the Earth Probe Total Ozone Monitoring Spectrometer (EP-TOMS) from January 1997 to December 2005; the Microwave Limb Sounder from October 2004 to April 2013; the Ozone Monitoring Interferometer (OMI) from October 2004 to December 2013; the Global Ozone Monitoring Experiment-2 (GOME-2) from January 2007 to December 2013; and the Infrared Atmospheric Sounding Interferometer (IASI) from June 2008 to December 2011, were used in this study together with ground-based measurement from a Dobson instrument (August 1989 to December 2011). The seven satellite and ground-based instruments used for this study were selected as they provide long term ozone monitoring data. Satellite observations were collected when they overpass Irene and showed that ToZ replicated the expected behavior of spring maximum and autumn minimum. When compared with other satellite data sets, TOMS ToZ data displayed values approximately 8 DU higher overall but showed good general agreement with measurements from the ground-based Dobson instrument. The OMI instrument had the best agreement with the Dobson instrument as the measurements are within 5 DU for all seasons. The result of trend trend analysis of ozone over Irene shows a significant decrease of ~8 DU in total ozone from 1978 to 1993 with a gradual recovery and increase of ~2 DU in total ozone from 1995 to 2005 as measured by both GOME-1 and EPTOMS. An increase of approximately 7-9 DU is observed in measurements from OMI and IASI thereby illustrating the gradual recovery of the ozone layer. EPTOMS also showed good agreement with the Dobson instrument. GOME-1 and GOME-2 reveal underestimation of ozone while IASI overestimated ozone for the first half of the year. Between 1995 and 2005, both EPTOMS and GOME-1 data showed a gradual increase in column ozone of approximately 2 DU which has increased to approximately 7 DU in the last decade as measured by OMI, GOME-2 and IASI satellites. The result obtained showed a very strong correlation (~97%) between the variation in OMI-Dobson and GOME-2-Dobson and (~85%) between the variation in EPTOMS-Dobson and GOME-1-Dobson.

Based on the measurements of precipitable water vapor (PWV) and total column ozone (TCO) from the MODIS satellite instruments (Aqua/Terra platforms), the connections between the North Atlantic Oscillation (NAO) and the anomalies in PWV and TCO over European Russia (ER) in summer 2010 are analyzed. It is found that the PWV (TCO) anomalies over the northern ER in summer 2010 positively (negatively) correlated with the NAO, and the local correlations reached 0.68 (–0.55). The physical mechanisms of the correlations are discussed. A comparative analysis of the relationships between the NAO and the regional PWV and TCO anomalies over ER during the summer seasons of 2000–2015 is carried out.

This paper reports investigation data on the temporal variability of total ozone content (TOC) in the Central Asian and Tibet Plateau mountain regions obtained by conventional methods, as well as by spectral, cross-wavelet, and composite analyses. The data of ground-based observation stations located at Huang He, Kunming, and Lake Issyk-Kul, along with the satellite data obtained at SBUV/SBUV2 (SBUV merged total and profile ozone data, Version 8.6) for 1980–2013 and OMI (Ozone Monitoring Instrument) and TOU (Total Ozone Unit) for 2009–2013 have been used. The average relative deviation from the SBUV/SBUV2 data is less than 1% in Kunming and Issyk-Kul for the period of 1980–2013, while the Huang He Station is characterized by an excess of the satellite data over the ground-based information at an average deviation of 2%. According to the Fourier analysis results, the distribution of amplitudes and the periods of TOC oscillations within a range of over 14 months is similar for all series analyzed. Meanwhile, according to the cross-wavelet and composite analyses results, the phase relationships between the series may considerably differ, especially in the periods of 5–7 years. The phase of quasi-decennial oscillations in the Kunming Station is close to the 11-year oscillations of the solar cycle, while in the Huang He and Issyk-Kul stations the TOC variations go ahead of the solar cycle.

Considering the potential importance of the concentration of ozone in the atmosphere and threat to its depletion in Pakistan’s environment, AQUA-AIRS Level-3 Daily Global satellite data is used to monitor the Total Column Ozone (TCO) over the entire region of the country. During 2003–2011 with spatial resolution of 1ox 1o lat/long grid, inter-annual analysis of TCO over the area (62°-76°E and 23°-37°N) showed that overall average distribution of TCO alterations are dependent on latitude and varied from 275 to 278 DU in the regions of Sindh and Baluchistan province with 297–300 DU in the northern and KPK province regions. Seasonal variations have shown that in the region 23°-29°N, highest concentration of ozone is recorded in summer season (JJA) and lowest in winter season (DJF) with mixed trend in both spring (MAM) and autumn (SON) seasons whereas in the region between 30°-37°N, maximum is recorded in winter (DJF) and spring (MAM) seasons with minimum in summer (JJA) and autumn (SON) seasons respectively. Statistical analysis revealed that linear relationship exists between year to year TCO and solar activity.

The Arosa site is well known in the ozone community for its continuous total ozone column observations that have been recorded since 1926. Originally based on Dobson sun spectrophotometers, the site has been gradually complemented by three automatic Brewer instruments, in operation since 1998. To secure the long-term ozone monitoring in this Alpine region and to benefit from synergies with the World Radiation Center, the feasibility of moving this activity to the nearby site at Davos (aerial distance of 13 km) has been explored. Concerns about a possible rupture of the 90-year-long record has motivated a careful comparison of the two sites, since great attention to the data continuity and quality has always been central to the operations of the observatory at Arosa. To this end, one element of the Arosa Brewer triad has been set up at the Davos site since November 2011 to realize a campaign of parallel measurements and to study the deviations between the three Brewer instruments. The analysis of the coincident measurement shows that the differences between Arosa and Davos remain within the range of the long-term stability of the Brewer instruments. A nonsignificant seasonal cycle is observed, which could possibly be induced by a stray-light bias and the altitude difference between the two sites. These differences are shown to be lower than the short-term variability of the time series and the overall uncertainty from individual Brewer instruments and therefore are not statistically significant. It is therefore concluded that the world's longest time series of the total ozone column obtained at Arosa site could be safely extended and continued with measurements taken from instruments located at the nearby Davos site without introducing a bias to this unique record.