Total Column Ozone Trends Research Articles

Total column ozone trends from the NASA Merged Ozone time series 1979 to 2021 showing latitude-dependent ozone recovery dates (1994 to 1998)

Abstract. Monthly averaged total column ozone data (ΩMOD(t,θ)) from the NASA Merged Ozone Data Set (MOD) were examined to show that the latitude-dependent (θ) ozone depletion turnaround dates (TA(θ)) range from 1994 to 1998. TA(θ) is defined as the approximate date when the zonally averaged ozone ceased decreasing. ΩMOD data used in this study were created by combining data from Solar Backscattered Ultraviolet instruments (SBUV/SBUV-2) and the Ozone Mapping and Profiler Suite (OMPS-NP) from 1979 to 2021. The newly calculated systematic latitude-dependent hemispherically asymmetric TA(θ) shape currently does not appear in the suite of chemistry–climate models that are part of the Chemistry–Climate Model Validation Activity (CCMVal), which combines the effects of photochemistry, volcanic eruptions, and dynamics in their estimate of ozone recovery. Trends of zonally averaged total column ozone in percent per decade were computed before and after TA(θ) using two different trend estimate methods that closely agree, Fourier series multivariate linear regression and linear regression on annual averages. During the period 1979 to TA(θ), the most dramatic rates of Southern Hemisphere (SH) ozone loss were PD=-10.9±3 % per decade at 77.5∘ S and -8.0±1.1 % per decade at 65∘ S, which is about double the Northern Hemisphere (NH) rate of loss of PD=-5.6±4 % per decade at 77.5∘ N and 4.4±1 % per decade at 65∘ N for the period 1979 to TA(θ). After TA(θ), there was an increase at 65∘ S of PD=1.6±1.4 % per decade with smaller increases from 55 to 25∘ S and a small decrease at 35∘ N of -0.4±0.3 % per decade. Except for the Antarctic region, there only has been a small recovery in the SH toward 1979 ozone values and almost none in the NH.

Trends and variability of total column ozone in the Third Pole

The Hindu Kush Himalaya and Tien Shan Mountain regions together are called the Third Pole (TP) of Earth, which encompasses ecologically fragile regions of 12 Asian countries. It is the highest mountain chain with the largest reserve of fresh ice mass on the planet outside the northern and southern polar regions. The TP region is experiencing high rate of glacier melting due to climate change for the past few decades, and is a great concern for water security of South Asia. Since changes in ozone concentrations in the atmosphere affect public health, ecosystem dynamics and climate, it is imperative to monitor its temporal evolution in an ecologically sensitive region such as TP. Here, the spatiotemporal characteristics of total column ozone (TCO) in TP and 20 selected cities in and around TP are investigated using a combined long-term data made from the satellite measurements of Ozone Monitoring Instrument (OMI) and Global Ozone Monitoring Experiment (GOME)-2B for the period 2005–2020. The spatial trends in TCO over TP are mostly negative in summer and autumn (from −0.2 DU/yr to −0.6 DU/yr), but positive in winter (up to +0.2 DU/yr). Among the selected 20 urban regions, the highest annual trend −0.42 ± 0.3 DU/yr and the lowest −0.01 ± 0.2 DU/yr are estimated in Xining and Chittagong, respectively. Analysis using a multiple regression model reveals that the ozone variability in TP is mostly driven by tropopause height with a contribution of 24.92%, Quasi-Biennial Oscillation (23.42%), aerosols (16.12%) and solar flux (15.34%). Our study suggests that the observed negative trend is mainly associated with human activities and climate change in TP, which would likely to enhance the surface temperature and thus, melting of glaciers in the region.

Spatiotemporal Variation, Driving Mechanism and Predictive Study of Total Column Ozone: A Case Study in the Yangtze River Delta Urban Agglomerations

Total column ozone (TCO) describes the amount of ozone in the entire atmosphere. Many scholars have used the lower resolution data to study TCO in different regions, but new phenomena can be discovered using high-precision and high-resolution TCO data. This paper used the long time, high accuracy, and high-resolution MSR2 dataset (2000–2019) to analyze the spatial and temporal variation characteristics of TCO over the Yangtze River Delta Urban Agglomeration to explore the relationship between the TCO and meteorological and socio-economic factors. The correlations between the TCO and climatic factors and the driving forces of meteorological and socio-economic factors on the spatial and temporal variability of TCO were also analyzed, and different mathematical models were constructed to fit the TCO for the past 20 years and predict the future trend of the TCO. The results show the following. (1) The TCO over the study area exhibited a quasi-latitudinal distribution, following a slight downtrend during 2000–2019 (0.01 ± 0.18 DU per year) and achieved its maximum in 2010 and minimum in 2019; throughout the year, an inverted V-shaped cycle characterizes the monthly variability of TCO; TCO was significantly higher in spring than in summer and autumn than winter. (2) Precipitation and the absorbed aerosol index (AAI) had critical effects on the spatial distribution of TCO, but meteorological factors were weakly correlated with the annual variation of TCO subject to the game interactions between different external driving factors. The monthly changes in the TCO were not in synergy with that of other meteorological factors, but with a significant hysteresis effect by 3–5 months. Socio-economic factors had a significant influence on TCO over the study area. (3) The Fourier function model can well describe the history and future trend of the annual TCO over the study area. The TCO over the study area shows a fluctuating upward trend (0.27 ± 1.35 DU per year) over the next 11 years. This study enriches the theoretical and technical system of ozone research, and its results can provide the necessary theoretical basis for ozone simulation and forecasting.

Response and periodic variation of total atmospheric ozone to solar activity over Mountain Waliguan

Modern-Era Retrospective Analysis for Research and Applications, Version-2 (MERRA-2) total column ozone (TCO) data from 1980 to 2018 and ground based TCO data were used to investigate its responses to periodic variations concerning stratospheric dynamics such as tropopause heights and Quasi-Biennial Oscillations (QBO), and solar activity signatures of Magnesium II core-to-wing ratio (Mg II) and F10.7 cm solar radio flux (F10.7) observed over Mountain (Mt.) Waliguan (36.17°N, 100.53°E), China. Cross-correlation and wavelet analyses were used for carrying out the investigation. The MgII and F10.7 show a periodicity of around an 11-year solar cycle (SC) while the TCO trend is though periodic and it does not exhibit one to one correspondence with the 11-year SC. The highest value in TCO is 355.7 DU noted in February (1982) whereas, the lowest value of TCO is 256.02 DU in October (1988) during the entire study period. The average value in TCO is 291.17 ± 0.94 DU with an amplitude of variation of 99.68 DU (~28%). The trend of TCO depicts a persistent distinct seasonal pattern with maxima in winter/spring (December through April) and minima in summer/autumn (August through November). The long-term variability shows a notable decreasing trend in TCO by ~30%, 13%, and 5% per decade for SCs 21–23, where SC 24 represents an increasing trend of ~1% per decade. Hence, this illustrates the significant recovery of TCO over Mt. Waliguan, China which is as a result of the reduction of the ozone depletion agents arising as a positive outcome of the implementation of the Montreal regulatory policy. From wavelet analysis, the F10.7, MgII, tropopause height, QBO and TCO show a significant dominant periodicity of 10–12 months. It is concluded that the variations in mean TCO are strongly correlated with variations of the F10.7 cm and Mg-II solar indices, and the mean TCO responds rapidly to solar activity variations.

Impact of solar and geomagnetic activities on total column ozone in China

Dynamic impacts on sunspot number (SSN), solar radio flux at 10.7 cm (F10.7) and amplitude antipodal (aa) index influencing long-term trends of total column ozone (TCO) obtained from three stations; Xianghe (39.975°N, 116.37°E), Linan (30.3°N, 119.73°E), and Kunming (25.03°N, 102.683°E) over China have been studied. Descriptive, regression and neural network training techniques are used from 1980 to 2018. The annual mean TCO concentrations are 333.61 ± 1.15 DU, 280.87 ± 0.58 DU, and 260.33 ± 0.49 DU at Xianghe, Linan, and Kunming stations, respectively. The mean monthly peak TCO values are ~417.13 DU (March), 316.79 DU (April), and 291.03 DU (April) at Xianghe, Linan, and Kunming, respectively. Irrespective of the decreasing seasonal trend during spring at Xianghe, the springtime TCO amount is greater than the TCO values in other seasons at all stations. Our analyses show direct forcing of SSN, F10.7, and aa on TCO changes throughout the different periods considered. At Xianghe, the value of r ranges between 0.09 and 0.48 and the p-value < 0.05 whereas the most contributing factor is aa index (about 40 %) to ozone enhancement. There is a dramatic improvement of the impact of the quasi-biennial oscillation (QBO)-modulated (70 hPa and 50 hPa) SSN, F10.7, and aa on TCO during winter in all the stations particularly the aa, which appreciated from ~40 % to 66 %. Ozone is affected negatively during descending and low solar cycle (SC) phases whereas it enhances during ascending and high SC phases with 30 hPa QBO as the most active force of enhancement. Our finding is a profitable tool for atmospheric model development, which could be used to predict future phenomena.

Supplementary material for 'Reevaluation of total-column ozone trends and of the Effective Radiative Forcing of ozone-depleting substances'

Supplementary material for 'Reevaluation of total-column ozone trends and of the Effective Radiative Forcing of ozone-depleting substances'

CCMI-1 모형에서의 동아시아 전량오존 및 대류권오존 평가

We assess Total Column Ozone (TCO) and Tropospheric Ozone (TRO) reproduced by the Chemistry Climate Model Initiative phase 1 (CCMI-1) project using ground-based observations and reanalysis datasets from 2003 to 2010 for East Asia. Five models, CESM1-WACCM, CESM1-CAM4Chem, HadGEM3-ES, MRI-CGCM3, and GEOSCCM, are evaluated. The multi-model mean of the five models reproduces a spatial distribution and seasonal cycle of TCO similar to the observation and reanalysis results. CCMI-1 models present a relative bias of TCO in the range of -4.22 to 0.47% against the observation data. Contrary to TCO, TRO shows a comparatively large inter-model spread in spatial pattern and seasonality. Indeed, the relative bias of TRO from the models is from -8.37 to 13.71% compared to the observation data. While CESM1-CAM4Chem and MRI-ESM1r1 produce reasonable spatial and temporal variability of TCO and TRO, HadGEM3-ES and GEOSCCM exhibit a bias with substantially lower and higher TRO in most seasons, respectively. Long-term trends in TCO and TRO are not significant in either reanalysis or CCMI models. These results suggest that TCO and TRO reproduction from CCMI-1 models requires caution and further evaluation, particularly for regional analysis.

Analysis of Long Term Variation of the Total Column and Tropospheric Ozone over the Indian Region

Ozone plays a significant part in regulating climate change and the chemical characteristics of the atmosphere. Changes in atmospheric ozone can be studied in more detail using ground-based and satellite-based instruments. Studies on the long-term global changes in total column ozone have begun more than three-decade ago using satellite data. The main objective of this work is to analyze the Total Column Ozone (TCO) variations, and tropo-spheric ozone variations over different twenty locations in the Indian sub-continent by using Total Ozone Mapping Spectrometer (TOMS) and AURA OMI/MLS data. The long-term analysis of total column ozone is divided into two phases (1979-1994 and 2005-2018), and tropospheric ozone for one phase (2005-2018) in order to detect changes in the ozone trend pattern. The results of linear regression analysis show a declining trend of total column ozone, and an increasing trend of tropospheric ozone over the selected locations. The impact of wind pattern on the variation of ozone has been analyzed by using NCEP reanalysis data, and found that wind patterns played a prominent role in spatial and temporal changes in total and tropospheric ozone distribution over the subcontinent. Latitudinal variation of total column ozone from Nagarcoil to Anantanag has also been studied for the years 1979, 1994, 2005, and 2018, which indicates an increase in ozone concentration with latitude.

Variability of Total Column Ozone with Solar Activity Features at Northern and Eastern Regions of India

A statistical study of Total Column Ozone (TCO) with Different solar activity features (DSAF), viz. sunspot number, solar flare, solar active prominences for a Northern station Shimla (31°10'N, 77°17'E) and an Eastern station Imphal (24°82'N, 93°94'E) of India is presented using 11 years (2004-2016) of data. In this study we have compared the trends in TCO with DSAF annually as well as for seasonal months. Our study shows a negative correlation between TCO and DSAF. A negative correlation suggests that there is decrease in Ozone concentration during the given time period with solar activity.

Monitoring and Long-term Trend of Total Column Ozone from Dobson Spectrophotometer in Seoul (1985~2017)

Monitoring and Long-term Trend of Total Column Ozone from Dobson Spectrophotometer in Seoul (1985~2017)

Statistical analysis of total column ozone during three recent solar cycles over India

Total column ozone (TCO) distribution and its variation over the Indian region at different stations for the period of about 30 years from 1986 to 2015 are studied. TCO data is taken from the merged ozone data set (MOD) overpass data for 15 different stations over India. The average correlation between TCO and solar proxies such as sunspot number and F10.7 cm solar flux is more than 0.5. We further divided the time series of TCO according to solar cycle as 22nd solar cycle (September 1986 to July 1996), 23rd solar cycle (August 1996 to November 2008) and 24th solar cycle (December 2008 to December 2015) (on going cycle) for a period of 1986–2015. Herein, for the long term trend analysis of TCO, we have removed the seasonal effect by the deseasonalization process, the effects of solar activities, stratospheric waves (quasi-biennial-oscillation-QBO and El Niño–Southern Oscillation-ENSO) by the multifunction linear regression method (MLR). We have compared both the linear trends in TCO which are calculated by the simple linear regression (SLR) and deseasonalised multifunction linear regression (DMLR) analysis. It is found that the direction of the trend in 22nd and the 23rd solar cycle is similar while, it is opposite in the 24th solar cycle. We observed a more negative trend in the 22nd solar cycle and less negative trend in the 23rd solar cycle while the trend is positive in the 24th solar cycle. The results indicate that after the DMLR process, the trend values are decreased by a large factor. Therefore, it is found that the role of natural variability is more than that of the ozone depleting substances (ODS) on long term variability in TCO over India. This statistical analysis provides better analysis of trend variation in TCO series over India. The main objective of this work is to analyze the variations in trend in the TCO with respect to the recent three solar cycles.

Zonally asymmetric trends of winter total column ozone in the northern middle latitudes

Using various satellite-based observations, a linear ozone transport model (LOTM), a chemistry-climate model (WACCM3) and an offline chemical transport model (SLIMCAT), zonally asymmetric trends of the total column ozone (TCO) in the northern middle latitudes during winter for the period 1979–2015 are analyzed and factors responsible for the trends are diagnosed. The results reveal that there are significant negative TCO trends over the North Pacific and positive TCO trends over the northwestern North America. The zonally asymmetric TCO trends are mainly contributed by the trends in partial column ozone in the upper troposphere and lower stratosphere (UTLS) which are closely related to the long-term changes of geopotential height in the troposphere. Furthermore, the trends of geopontential height in the UTLS are mainly modulated by pattern changes in the Arctic Oscillation (AO), the Cold Ocean–Warm Land (COWL) and the North Pacific (NP) index. Accordingly, the zonally asymmetric TCO trends can be largely reconstructed by the trends of the above three teleconnection patterns. Sea surface temperature (SST) changes over the Pacific Ocean and the Atlantic Ocean can also exert a significant contribution to the zonally asymmetric TCO trends through their influence on the COWL and NP patterns. In addition, chemical ozone loss partially offsets the positive trends in zonal TCO anomalies over Central Siberia and enhances the positive TCO trends over northwestern North America. However, the contribution of chemical processes to the zonally asymmetric TCO trends is relatively smaller than that of dynamical transport effects. Interpreting the zonally asymmetric TCO trends and their responsible factors would be helpful for accurately predicting the stratospheric ozone return date in the northern middle latitudes.

On ozone trend detection: using coupled chemistry–climate simulations to investigate early signs of total column ozone recovery

Abstract. Total column ozone values from an ensemble of UM-UKCA model simulations are examined to investigate different definitions of progress on the road to ozone recovery. The impacts of modelled internal atmospheric variability are accounted for by applying a multiple linear regression model to modelled total column ozone values, and ozone trend analysis is performed on the resulting ozone residuals. Three definitions of recovery are investigated: (i) a slowed rate of decline and the date of minimum column ozone, (ii) the identification of significant positive trends and (iii) a return to historic values. A return to past thresholds is the last state to be achieved. Minimum column ozone values, averaged from 60° S to 60° N, occur between 1990 and 1995 for each ensemble member, driven in part by the solar minimum conditions during the 1990s. When natural cycles are accounted for, identification of the year of minimum ozone in the resulting ozone residuals is uncertain, with minimum values for each ensemble member occurring at different times between 1992 and 2000. As a result of this large variability, identification of the date of minimum ozone constitutes a poor measure of ozone recovery. Trends for the 2000–2017 period are positive at most latitudes and are statistically significant in the mid-latitudes in both hemispheres when natural cycles are accounted for. This significance results largely from the large sample size of the multi-member ensemble. Significant trends cannot be identified by 2017 at the highest latitudes, due to the large interannual variability in the data, nor in the tropics, due to the small trend magnitude, although it is projected that significant trends may be identified in these regions soon thereafter. While significant positive trends in total column ozone could be identified at all latitudes by ∼ 2030, column ozone values which are lower than the 1980 annual mean can occur in the mid-latitudes until ∼ 2050, and in the tropics and high latitudes deep into the second half of the 21st century.

Assessment of total columnar ozone climatological trends over the Indian sub-continent

ABSTRACTIn the present study, long term satellite and Dobson spectrophotometer Total Column Ozone (TCO) data have been used to study the interannual variability and also to assess climatological trends in TCO over different geographical locations of Indian sub-continent. TCO data were analyzed for the period 1957 to 2015 over New Delhi (28.63° N, 77.18° E), Varanasi (25.30° N, 83.02° E), Pune (18.53° N, 73.84° E) and Kodaikanal (10.0° N, 77.47° E). An extensive validation was performed for Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) retrieved TCO data independently with Dobson Spectrophotometer TCO measurements over New Delhi, Varanasi, Pune and Kodaikanal. The results of this exercise showed good correlation coefficient (r) of 0.87 (0.88), 0.84 (0.82), 0.91 (0.80) and 0.84 (Data not available) respectively. Climatological mean TCO over New Delhi, Varanasi, Pune and Kodaikanal are 275.02 ± 6.44 DU, 269.03 ± 7.34 DU, 260.78 ± 5.07 DU and 258.71 ± 6.36 DU respectively for the period 1957 to 2015. An increasing trend over New Delhi (0.20 DU year–1), Pune (0.18 DU year–1), Kodaikanal (0.14 DU year–1) and decreasing trend over Varanasi (0.01 DU year–1) were observed. High significance of TCO trend was found at New Delhi (p-value < 0.0001), Pune (p-value = 0.002) and Kodaikanal (p-value = 0.003) with negligible trend over Varanasi with p-value of 0.84. The TCO variations at different geographical locations associated with upper atmospheric meteorological parameters such as lower Stratospheric Temperature (ST) at 65 hPa and Tropopause Height (TH) were also addressed. Annual lower stratospheric temperature shows positive relationship with TCO and Stratospheric ozone over the study sites. Further, decadal variability in TCO with respect to solar activity at New Delhi was also analyzed.

A more representative “best representative value” for daily total column ozone reporting

Abstract. Long-term trends of total column ozone (TCO), assessments of stratospheric ozone recovery, and satellite validation are underpinned by a reliance on daily best representative values from Brewer spectrophotometers and other ground-based ozone instruments. In turn reporting of these daily total column ozone values to the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) has traditionally been predicated upon a simple choice between direct sun (DS) and zenith sky (ZS) observations. For mid- and high-latitude monitoring sites impacted by cloud cover we discuss the potential deficiencies of this approach in terms of its rejection of otherwise valid observations and capability to evenly sample throughout the day. A new methodology is proposed that makes full use of all valid direct sun and zenith sky observations, accounting for unevenly spaced observations and their relative uncertainty, to calculate an improved estimate of the daily mean total column ozone. It is demonstrated that this method can increase the number of contributing observations by a factor of 2.5, increases the sampled time span, and reduces the spread of the representative time by half. The largest improvements in the daily mean estimate are seen on days with the smallest number of contributing direct sun observations. No effect on longer-term trends is detected, though for the sample data analysed we observe a mean increase of 2.8 DU (0.82 %) with respect to the traditional direct sun vs. zenith sky average choice. To complement the new calculation of a best representative value of total column ozone and separate its uncertainty from the spread of observations, we also propose reporting its standard error rather than the standard deviation, together with measures of the full range of values observed.

Statistical bias correction for creating coherent total ozone record from OMI and OMPS observations

Abstract A long-term coherent total column ozone (TCO) record is essential to ozone layer variability assessment, especially the detection of early signs of ozone recovery after years of depletion. Because of differences in satellite platforms and instruments design, calibration, and retrieval algorithms, however, significant cross-mission biases are observed between multiple sensor TCO observations in the common time–space domain. To attain a coherent TCO record, observed cross-mission biases should be accurately addressed prior to the data-merging scheme. In this study, a modified statistical bias correction method was proposed based on the quantile-quantile adjustment to remove apparent cross-mission TCO biases between the Ozone Monitoring Instrument (OMI) and Ozone Mapping and Profiler Suite (OMPS). To evaluate the effectiveness of this modified algorithm, the overall inconsistency (OI), a unique time-series similarity measure, was proposed to quantify the improvements of consistency (or similarity) between cross-mission TCO time series data before and after bias correction. Common observations during the overlapped time period of 2012–2015 were used to characterize the systematic bias between OMPS and OMI through the modified bias correction method. TCO observations from OMI during 2004–2015 were then projected to the OMPS level by removing associated cross-mission biases. This modified bias correction scheme significantly improved the overall consistency, with an average improvement of 90% during the overlapped time period at the global scale. In addition to the evaluation of consistency improvements before and after bias correction, impacts of cross-mission biases on long-term trend estimations were also investigated. Comparisons of derived trends from the merged TCO time series before and after bias correction across 38 ground-based stations indicate that cross-mission biases not only affect magnitudes of estimated trends, but also result in different phases of trends. Further comparisons of estimated seasonal TCO trends before and after bias correction at the global scale suggest that trends derived from the bias-corrected time series are more accurate than those without bias correction. Overall, the bias correction scheme developed in this study is essential for preparing an accurate long-term TCO record representative of trend analysis to support future assessment of ozone recovery at the global scale.

Total Column Ozone Variability and Trends over Kenya using Combined Multiple Satellite-Based Instruments

We investigate the trends and variability in Total Column Ozone (TCO) over three Kenyan cities; Nairobi (1.17o S; 36.46o E), Kisumu (0.03o S; 34.45o E) and Mombasa (4.02o S; 39.43o E) from 1985 – 2011 using TCO data from combined multiple satellite-based instruments to create a single near-global daily time series. Monthly, annual and seasonal means are calculated based on the measures of TCO daily values. A visual depiction of the trends and variability in TCO is provided by means of the time series. Annual, monthly and seasonal trends in TCO are calculated from straight line fits whereby the net ozone changes over the 27 years analysis can be determined. Quantification of the observed changes in TCO percentage variability is also calculated. Annual means and standard deviations of TCO estimated at Nairobi, Kisumu and Mombasa are 254.75 ± 5.17 DU, 253.92 ± 5.20 DU and 257.07 ± 4.70 DU respectively. Over the period 1985 – 2011 a decreasing trend of 0.031% year -1 is observed at Nairobi, 0.026% year -1 at Kisumu and 0.031% year 1 at Mombasa equating to losses of 2.158 DU at Nairobi, 1.759 DU at Kisumu and 2.164 at Mombasa. TCO annual variability ranges between 1% and 6%, while the seasonal variability ranges between 2% and 4%. The slope of the line of fit exhibit a negative sign showing a statistically decreasing trend over time in all the three locations under study, hence, temporal variability of TCO in all the three cities is declining.

Trend of total column ozone over Mexico from TOMS and OMI data (1978-2013)

Using satellite measurements from the Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) version 8, this work presents the total column ozone (TCO) trends over Mexico and, in particular, over the state of Zacatecas. Interannual variations and their statistical dispersion show a surprisingly systematic behavior. Yearly low values occur during December and January, while high values between April and May. A significant depletion of about 2.5% in TCO between 1978 and 1994 is derived from their statistical analysis, which also shows stabilization from 1996 to 2013. Although the depletion is merely significant, it is a sign that the studied regions, crossed by the Tropic of Cancer, have not escaped to the depletion of the ozone layer. The characterization described herein is important in terms of the correlation of TCO and ultraviolet radiation levels.

Ozone trends derived from the total column and vertical profiles at a northern mid-latitude station

Abstract. The trends and variability of ozone are assessed over a northern mid-latitude station, Haute-Provence Observatory (OHP: 43.93° N, 5.71° E), using total column ozone observations from the Dobson and Système d'Analyse par Observation Zénithale spectrometers, and stratospheric ozone profile measurements from light detection and ranging (lidar), ozonesondes, Stratospheric Aerosol and Gas Experiment (SAGE) II, Halogen Occultation Experiment (HALOE) and Aura Microwave Limb Sounder (MLS). A multivariate regression model with quasi-biennial oscillation (QBO), solar flux, aerosol optical thickness, heat flux, North Atlantic Oscillation (NAO) and a piecewise linear trend (PWLT) or equivalent effective stratospheric chlorine (EESC) functions is applied to the ozone anomalies. The maximum variability of ozone in winter/spring is explained by QBO and heat flux in the ranges 15–45 km and 15–24 km, respectively. The NAO shows maximum influence in the lower stratosphere during winter, while the solar flux influence is largest in the lower and middle stratosphere in summer. The total column ozone trends estimated from the PWLT and EESC functions are of −1.47 ± 0.27 and −1.40 ± 0.25 DU yr−1, respectively, over the period 1984–1996 and about 0.55 ± 0.30 and 0.42 ± 0.08 DU yr−1, respectively, over the period 1997–2010. The ozone profiles yield similar and significant EESC-based and PWLT trends for 1984–1996, and are about −0.5 and −0.8% yr−1 in the lower and upper stratosphere, respectively. For 1997–2010, the EESC-based and PWLT estimates are of the order of 0.3 and 0.1% yr−1, respectively, in the 18–28 km range, and at 40–45 km, EESC provides significant ozone trends larger than the insignificant PWLT results. Furthermore, very similar vertical trends for the respective time periods are also deduced from another long-term satellite-based data set (GOZCARDS–Global OZone Chemistry And Related trace gas Data records for the Stratosphere) sampled at northern mid-latitudes. Therefore, this analysis unveils ozone recovery signals from total column ozone and profile measurements at OHP, and hence in the northern mid-latitudes.

Interannual variability and temporal variations of total column ozone in Visakhapatnam from ground based observations

Total column ozone (TCO) measured by the portable, handheld, multichannel Sun photometer (ozonometer-Microtops-II) at Visakhapatnam (17.43°N, 83.14°E; 51 m above mean sea level), India, which is a tropical urban station has been analysed in this study. The results showed the estimate of the annual and seasonal trends of TCO from the period February 2005 to December 2008. The linear regression technique was applied in Microtops II data to study the trend of TCO during 2005–2008. It also provides statistics of mean and variability on temporal scale. The results showed increasing trend at Visakhapatnam an average of 1.88 DU per year (or 0.61% per year). However the maximum deviation in diurnal variability of TCO were 28 DU (9.19%) while the minimum deviation were −36 DU (−11.8%) respectively, which is one of the unique result of this study. The range of the seasonal change represents 9.2% of the mean TCO value with maximum/minimum during March/December.