Variability Of Total Column Ozone Research Articles

Spatial and Temporal Variability of Total Column Ozone over the Indian Subcontinent: A Study Based on Nimbus-7 TOMS Satellite

The distribution and variability of ozone is very important to the atmospheric thermal structures, and it can exert their greater influence on climate. Present study is based on Nimbus-7 TOMS overpass column ozone for a period of 14 years (1979-1992) over twelve selected Indian stations from south to north latitude and it explores the spatial and temporal variability of Total Column Ozone (TCO). For this investigation an advanced statistical methods such as Factor Analysis and Morlet wavelet transform are employed. Total column ozone variability over these stations is grouped into two clusters (Eigen value greater than 1) by the Multivariate Factor analysis. It is found that the Group I stations shows the same nature of variability mainly due the first factor as the primarily loading and whereas as the Group II stations shows the same nature of variability due to second factor as the primary loading. The correlation value of TCO decreases from 0.9 to 0.32 as we move from south to north stations (lower latitude to higher latitude). The total column ozone over tropical stations is maximum during monsoon season with peak in the month of June and that for the higher latitude stations is during the pre-monsoon season. Annual average of TCO for tropical stations is about 265 DU and that for subtropical stations is about 280 DU and a difference of 15 DU is noted in the annual average of TCO between tropical and subtropical stations. A large reduction in TCO is noted over the Indian subcontinent in the year 1985, the same year in which the ozone hole over Antarctica was discovered. It is also found that two prominent oscillations are present in total column ozone one with a periodicity of 16 to18 months and other with 28 to 32 months (QBO periodicity) apart from the annual oscillations. These oscillations are found to be significant at above 95% level of confidence when tested with Power Spectrum method. Tropical TCO shows high concentration during the westerly phase and low concentration during the easterly phase of the equatorial stratospheric quasi-biennial oscillation.

Analysis of temporal and spatial variability of total column ozone over West Africa using daily TOMS measurements

The aim of this study was to examine the temporal and spatial total column ozone distribution in West Africa using Total Ozone Mapping spectrometer (TOMS) daily data for five years between 2001 and 2005 in fifteen locations. In this study, certain significant observations emerged: weather activity particularly the rainfall producing mechanism (dynamic of the wind systems) was responsible for about 62% ozone distribution in the region. Ozone maximum and minimum concentrations over all the stations were 305 DU and 232 DU respectively producing an average range of 73 DU (only about 27.03% of the mean value). Ozone has a seasonal distribution with minimum occurring during the dry season and maximum occurring during the wet season. A decreasing rate of about –0.6 DU/year was found for the region. Interannual ozone characteristics revealed an oscillating feature similar to Quasi – biennial Oscillation (QBO) footprints which indicated the importance of stratosphere – troposphere exchange to ozone distribution in the region. Furthermore, lag of about one or two months occurs between south (lower latitude) and north (higher latitude) monthly ozone maximums.

Contribution of some ozone depleting substances (ODS) and greenhouse gases (GHGs) on total column ozone growth at Srinagar (34°N, 74.8°E), India

A critical analysis has been made on the contribution of CFC-11, CFC-12, CFC-113, CH3Cl, CH3Br, CCl4, CH3CCl3, HCFCs, halons, WMO (World Meteorological Organization) minor constituents, CH4, N2O and water vapour to the variation of total column ozone (TCO) concentration at the station in Srinagar (34°N, 74.8°E), India from 1992 to 2003. With the implementation of Montreal Protocol, though the concentrations of CFC-11, CFC-113, CH3Cl, CH3Br, CCl4 and CH3CCl3 had decreased, the concentrations of CFC-12, HCFCs, halons, WMO minor constituents, CH4, N2O and water vapour had increased, as a result of which TCO had risen from 1992 to 2003 at the above station. The nature of yearly variations of concentrations of the above ozone depleting substances and GHGs as well as ozone has been presented. Possible explanations for build-up of TCO have also been offered.

Ozone Variations over Central Tien-Shan in Central Asia and Implications for Regional Emissions Reduction Strategies

The variability of total column ozone (TCO) and tropospheric column ozone (TrCO) was examined in Central Asia. Measurements were conducted at the Lidar Station Teplokluchenka in eastern Kyrgyzstan for one year, July 2008–July 2009. TCO was obtained using a handheld Microtops II Ozonometer (TCO-MII) and from the Aura OMI (TCO-OMI) satellite. Nitrogen dioxide (NO2) and formaldehyde concentrations also were obtained from the OMI satellite. Formaldehyde was used as a surrogate for volatile organic compounds. TrCO was estimated by the difference between TCO-OMI and stratospheric column ozone retrieved from the MLS satellite. Comparison of the ground-based TCO-MII with TCO-OMI showed good agreement (r 2 = 0.93), and linear regression between these was used to estimate missing values in the TCO-MII dataset. The contribution of TrCO to TCO varied from 15% in summertime to 5% in winter. High values of TrCO were observed during summer (July: 45 DU) and low values during winter (December: 15 DU), as is typically observed. The average values of TrCO for summer, autumn, winter, and spring were equal to 42, 27, 20, and 30 DU, respectively. Seasonal variability of TrCO corresponded to solar intensity, indicating that TrCO is likely to form through photochemical means rather than stratospheric intrusion. The spatial distribution of NO2 and VOC were examined to better understand the regional sources of these ozone precursors. Transport from highly populated areas of the Ferghana Valley and Tashkent in Uzbekistan contributed to the TrCO concentrations observed in this work. The HCHO/NO2 ratio, an indicator of the ozone production rate, suggested that reducing NO2 would be more effective in reducing TrCO during most of the year, except summer, when reductions of both would likely be needed.

Factors affecting O3 and NO2photolysis frequencies measured in the eastern Mediterranean during the five‐year period 2002–2006

The photolysis frequencies of ozone (O3; to singlet oxygen, JO1D) and nitrogen dioxide (NO2; JNO2) were recorded at the remote coastal site Finokalia (35°20′N, 25°40′E), on the island of Crete, Greece, during the period 2002–2006. We present a study of their main climatological aspects and a quantification of the effect of aerosol and total ozone column on these frequencies. The 5‐yr mean Aerosol Optical Depth (AOD) at 380 nm in the area is equal to 0.27 ± 0.13 and reduces JNO2by 5%–14% at a solar zenith angle (sza) of 60°, compared to an aerosol‐free atmosphere. It also leads to a similar reduction of JO1D by 5%–15% at the 60° sza, for an average total ozone column (300–320 Dobson units (DU)). The effect of regional background AOD (∼0.1) is a reduction of JNO2 and JO1D by up to 6% for sza in the range 15° to75°, respectively. During high aerosol loads (AOD 0.5–0.7) the percentage reduction of Js was found to be as much as 30%–40% at high sza. The day‐to‐day variability of total ozone column over the area, of the order of 20 DU, was found to result in a 12% change in JO1D at 60° sza as compared with zero AOD conditions. A reduction of Js corresponding to a 24% decrease in the local noon JO1D value and a 5% decrease in local noon JNO2 were found to result in a 12% reduction in the 24 h mean net chemical production of O3, using a chemical box model.

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.

Evidence for the influence of the North Atlantic Oscillation on the total ozone column at northern low latitudes and midlatitudes during winter and summer seasons

[1] The strong influence of the winter North Atlantic Oscillation (NAO) on the total ozone column (TOC) in the Northern Hemisphere has been reported in a number of previous studies. In this study we show that this influence is not restricted to the winter season but is also significant in summer. Especially interesting effects of the summer NAO (SNAO) on the TOC are observed over the eastern Mediterranean region, where a strongly positive SNAO index is related to the creation of a geopotential height-negative anomaly over Greece with maximum amplitude at 200 hPa. Another anomaly was observed west of the Iberian Peninsula with similar effects on the TOC. Analyzing 26 years of Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) data from the equator to midlatitudes (60°) in the Northern Hemisphere, we demonstrate that the SNAO accounts for up to 30% of the TOC variability with a strong latitudinal and longitudinal dependence. Additionally, we obtain significant correlations between the NAO index and the thermal tropopause pressure and also with the geopotential heights at 200 and 500 hPa. Finally, some indirect connections between NAO and the TOC through teleconnections are also discussed.

Role of the rate of change of Total Column Ozone during different seasons on the prediction of Indian summer monsoon rainfall over Gangetic West Bengal, India

A critical analysis of Total Column Ozone (TCO) over Dum Dum, West Bengal, India is done during different seasons for the period of 1997 to 2005. It is confirmed that pre-monsoon rate of change of TCO over Dum Dum is highly correlated with Gangetic West Bengal, India monsoon rainfall of same year and that of TCO during other seasons are independent of monsoon rainfall over Gangetic West Bengal. It is also concluded that pre-monsoon rate of change of TCO may play an important role to forecast monsoon rainfall of a particular year over Gangetic West Bengal. It is also showed that other parameters affecting monsoon rainfall are insignificant w.r.t. TCO variations. A possible explanation based on chemical kinetics of O3 are also presented.

Temporal and spatial variability of total ozone column using TOMS satellite observations and comparison with measurements from the Dobson network

This article presents a detailed analysis of seasonal and interannual variability of total ozone content (TOC) at 16 different stations in Africa using Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) data for a period of 14 years (January 1979–December 1992). The analysis provides not only an estimate of the long-term annual and seasonal trends but also statistics of means and variability of ozone on temporal and spatial scales. For example, high negative deviations were observed for stations in Northern Africa in spring (March–May), with as much as –20 DU in Alexandria. A comparison of total ozone column data retrieved from the TOMS satellite with measurements obtained from the Dobson ground-based network is further presented for Cairo, Irene, Nairobi and Springbok. Estimates of the percentage seasonal difference between TOMS satellite and Dobson ground-based measurements reveal that the ground measurements were higher in magnitude at all stations with the exception of Nairobi. To verify the level of correlation between the ground-based and satellite observations, rank correlation coefficients were determined for all stations using daily and monthly observations. The results show that there is good correlation between the compared data sets, with daily coefficient of determination (r 2) values of 0.87, 0.76, 0.58 and 0.87 for Cairo, Irene, Nairobi and Springbok, respectively.

Variation of total column ozone along the monsoon trough region over north India

This study examined the total column ozone (TCO) variations over New Delhi (28.65° N, 77.217° E) and Varanasi (25.32° N, 83.03° E), which lie along the monsoon trough region, and over the tropical station Kodaikanal (10.23° N, 77.46° E), which lies outside the monsoon trough. Monthly, seasonal and annual TCO variations were determined using data from ground-based Dobson spectrophotometers during 2000–2008, Brewer spectrophotometers during 2000–2005 and the satellite-based Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) during 2002–2008. We found that Dobson, Brewer and SCIAMACHY TCO variations showed negative trends, indicating a decreasing tendency during the period studied at all three stations. Over Varanasi, the trend decreased further by about 3 DU year−1. Quasi-Biennial Oscillation (QBO) influences were seen in the time series of TCO over New Delhi and Varanasi, and weaker QBO signals over Kodaikanal. Comparisons were made between ground-based Dobson and Brewer spectrophotometer and SCIAMACHY satellite monthly mean TCO values. The differences between SCIAMACHY and Dobson TCO were 0.4–4.2% for New Delhi and 2.3–6.2% for Varanasi. The differences between SCIAMACHY and Brewer TCO values were 2.0–6.4% for Kodaikanal. In the peak monsoon months (July and August), decreases in TCO values over New Delhi and Varanasi (the monsoon trough region) may be due to the deep convection present during the monsoon season. During the monsoon season, several intense cyclonic systems appear over the monsoon trough region and may cause lowering of the TCO. Kodaikanal shows opposite features, with high values being observed during the peak monsoon months. TCO values over New Delhi were found to be higher than those over Varanasi and Kodaikanal, and TCO values over Varanasi were higher than over Kodaikanal. It was concluded that TCO values increase with increasing latitude.

Diurnal variability of total ozone column over Madrid (Spain)

In recent years, research on ozone variability has mainly focused on the analysis of its trend. Additionally some studies have analyzed the annual, seasonal and day-to-day ozone variations. However, intra-diurnal total ozone variations are notably less explored. Thus, the main objective of this paper is to analyze the diurnal variability of total ozone column (TOC) as recorded by a Brewer spectrophotometer in Madrid (Spain). The results show that about 90% of days present non-negligible diurnal variability, indicating that, in general, it should not be assumed that TOC remains constant throughout a particular day in urban areas. In addition, this variability has a notable seasonal behavior which should be considered (the spring and summer months show higher diurnal TOC variations than autumn and winter months). This pattern is likely caused by the diurnal photochemical processes in the lower troposphere related to the formation of tropospheric ozone near the earth’s surface at populated urban locations. Thus, these diurnal fluctuations in tropospheric ozone could explain part of diurnal TOC variations (between 20% and 70% depending on the mixing layer height).

A new ENSO index derived from satellite measurements of column ozone

Abstract. Column Ozone measured in tropical latitudes from Nimbus 7 total ozone mapping spectrometer (TOMS), Earth Probe TOMS, solar backscatter ultraviolet (SBUV), and Aura ozone monitoring instrument (OMI) are used to derive an El Nino-Southern Oscillation (ENSO) index. This index, which covers a time period from 1979 to the present, is defined as the "Ozone ENSO Index" (OEI) and is the first developed from atmospheric trace gas measurements. The OEI is constructed by first averaging monthly mean column ozone over two broad regions in the western and eastern Pacific and then taking their difference. This differencing yields a self-calibrating ENSO index which is independent of individual instrument calibration offsets and drifts in measurements over the long record. The combined Aura OMI and MLS ozone data confirm that zonal variability in total column ozone in the tropics caused by ENSO events lies almost entirely in the troposphere. As a result, the OEI can be derived directly from total column ozone instead of tropospheric column ozone. For clear-sky ozone measurements a +1 K change in Nino 3.4 index corresponds to +2.9 Dobson Unit (DU) change in the OEI, while a +1 hPa change in SOI coincides with a −1.7 DU change in the OEI. For ozone measurements under all cloud conditions these numbers are +2.4 DU and −1.4 DU, respectively. As an ENSO index based upon ozone, it is potentially useful in evaluating climate models predicting long term changes in ozone and other trace gases.

Total ozone column from direct and diffuse spectral solar irradiance in the southwest of the Iberian Peninsula

Daily total ozone column (TOC) measurements from the Brewer spectroradiometer located at El Arenosillo (Spain) and the Spectrometer for Atmospheric TRAcers Monitoring (SPATRAM) located at Évora (Portugal) are analyzed for the period 2006–2008. The main goal of this study is to compare TOC estimates retrieved with the passive differential optical absorption spectroscopy (DOAS) methodology from zenith‐sky observations by the SPATRAM spectrometer with highly accurate TOC estimates retrieved from direct‐sun recordings by a well‐calibrated Brewer instrument. On average, SPATRAM TOC estimates are (1.69 ± 0.18)% smaller than collocated Brewer TOC estimates. Significant relative differences between SPATRAM and Brewer total ozone data are detected in some periods caused by the influence of high aerosol load episodes over the SPATRAM data. Satellite data recorded by the ozone monitoring instrument (OMI)‐DOAS algorithm aboard the NASA EOS‐Aura satellite have been used to quantify the natural spatial variability of TOC over the region of interest as a potential source of uncertainty in the SPATRAM‐Brewer comparison. Our results show that the differences observed between both systems is not associated with the natural spatial variability of TOC. In addition, the OMI‐DOAS total ozone data have been compared to the ground‐based spectroradiometer data showing an excellent agreement for the Brewer spectroradiometer (R2 ∼ 0.95) and a fairly good agreement for the SPATRAM instrument (R2 ∼ 0.89).

Influence of the relative optical air mass on ultraviolet erythemal irradiance

The main objective of this article is to analyze the relationship between the transmissivity for ultraviolet erythemal irradiance (UVER) and the relative optical air mass at Badajoz (Southwestern Spain). Thus, a power expression between both variables is developed, which analyses in detail how atmospheric transmission is influenced by the total ozone column (TOC) and the atmospheric clearness. The period of analysis extends from 2001 to 2005. The experimental results indicate that clearness conditions play an important role in the relationship between UVER transmissivity and the relative optical air mass, while the effect of TOC is much smaller for this data set. In addition, the results show that UVER transmissivity is more sensitive to changes in atmospheric clearness than to TOC variability. Changes in TOC values higher than 15% cause UVER trasnmissivity to vary between 14% and 22%, while changes between cloud-free and overcast conditions produce variations in UVER transmissivity between 68% and 74% depending on the relative optical air mass.

Stratospheric variability and tropospheric ozone

Changes in the stratosphere‐troposphere exchange (STE) of ozone over the last few decades have altered the tropospheric ozone abundance and are likely to continue doing so in the coming century as climate changes. Combining an updated linearized stratospheric ozone chemistry (Linoz v2) with parameterized polar stratospheric clouds (PSCs) chemistry, a 5‐year (2001–2005) sequence of the European Centre for Medium‐Range Weather Forecasts (ECMWF) meteorology data, and the University of California, Irvine (UCI) chemistry transport model (CTM), we examined variations in STE O3 flux and how it perturbs tropospheric O3. Our estimate for the current STE ozone flux is 290 Tg/a in the Northern Hemisphere (NH) and 225 Tg/a in the Southern Hemisphere (SH). The 2001–2005 interannual root‐mean‐square (RMS) variability is 25 Tg/a for the NH and 30 Tg/a for the SH. STE drives a seasonal peak‐to‐peak NH variability in tropospheric ozone of about 7–8 Dobson unit (DU). Of the interannual STE variance, 20% and 45% can be explained by the quasi‐biennial oscillation (QBO) in the NH and SH, respectively. The CTM matches the observed QBO variations in total column ozone, and the STE O3 flux shows negative anomalies over the midlatitudes during the easterly phases of the QBO. When the observed column ozone depletion from 1979 to 2004 is modeled with Linoz v2, we predicted STE reductions of at most 10% in the NH, corresponding to a mean decrease of 1 ppb in tropospheric O3.

Sensitivity of UV Erythemally Effective Irradiance and Daily Dose to Spatial Variability in Total Ozone

The total ozone column (TOC) is the most significant quantity for estimating the erythemally effective UV radiation under clear sky conditions. Uncertainties in TOC measurements and a limited spatial and temporal resolution therefore influence the quality of calculated erythemally effective radiation. The UV Index, the internationally accepted measure of the erythemally effective radiation, is used in public and the media to inform about current levels of UV radiation and builds the base for sun protection. Thus, the accuracy of the promoted values is essential. While in a preceding study we estimated the influence of measurement uncertainties, in this study we analyze the influence of spatial gaps and variability of TOC to the erythemally effective irradiance at noon and to the daily dose. The results allow defining the necessary spatial resolution of TOC values when a certain accuracy for the UV Index or for the purpose of sun protection is required. In case of the erythemally effective irradiance this study reveals that spatial gaps in TOC or the assumption of spatial invariability causes similar uncertainties independent of the geographic location. At higher latitudes the higher spatial variability of TOC counteracts the lower level of irradiance. For the daily dose gaps in TOC have an even higher impact at higher latitudes.

Aerosol Optical Depth, Ozone and Water Vapor Measurements over Gadanki, A Tropical Station in Peninsular India

This paper reports the results of a study related to the optical and physical characteristics of columnar aerosols and variation in total column ozone (TCO) and precipitable water content (PWC) over Gadanki (13.45°N, 79.18°E), a tropical station in peninsular India, for the first time, using MICROTOPS-II (Microprocessor-based Total Ozone Portable Spectrometer), comprising of both sun photometer and ozonometer. Results show wavelength dependence of AOD, having mean value of ~0.4 (±0.09) at 500 nm optical channel. Daily mean aerosol size spectra shows, most of the time, power-law distribution. However, its diurnal variations show significant changes in aerosol size spectra modulated by a combination of both power-law and bi-modal distributions. To characterize AOD, the Angstrom parameters (i.e., α and β) were used. The day-to-day variations in TCO were found to be in fair agreement with that derived from TOMS satellite data for all the experimental days, having mean observed value of ~253 (±8) DU over the station. Interestingly, an inverse relationship between TCO and AOD or PWC was observed over the station, on some times of the day, which could be attributed to the mixing of significant fraction of ozone with aerosol and water vapor-rich air mass. However, a significant positive correlation was observed between AOD and PWC.

Spatial variation of total column ozone on a global scale

The spatial dependence of total column ozone varies strongly with latitude, so that homogeneous models (invariant to all rotations) are clearly unsuitable. However, an assumption of axial symmetry, which means that the process model is invariant to rotations about the Earth's axis, is much more plausible and considerably simplifies the modeling. Using TOMS (Total Ozone Mapping Spectrometer) measurements of total column ozone over a six-day period, this work investigates the modeling of axially symmetric processes on the sphere using expansions in spherical harmonics. It turns out that one can capture many of the large scale features of the spatial covariance structure using a relatively small number of terms in such an expansion, but the resulting fitted model provides a horrible fit to the data when evaluated via its likelihood because of its inability to describe accurately the process's local behavior. Thus, there remains the challenge of developing computationally tractable models that capture both the large and small scale structure of these data.

Seasonal variations in the spatial‐temporal dependence of total column ozone

AbstractThe Total Ozone Mapping Spectrometer (TOMS) is a satellite‐based instrument that measures total column ozone on a daily basis over a fairly dense spatial grid with near global coverage. Statistical models for the spatial‐temporal variations in total column ozone provide insights into ozone dynamics, are valuable for obtaining inferences on long‐term trends in ozone levels, and can be used to predict ozone levels at unobserved points in space‐time. However, developing such a model is complicated by the seasonally varying nature of the space‐time dependence and the partial confounding of spatial and temporal variation caused by the sun‐synchronous orbit of the satellite. This work considers methods for describing, modeling and estimating the seasonal patterns in the dependence structure for measurements at a single latitude. Applying one of these models to the synoptic prediction of total column ozone at a latitude shows that there is at least the potential for substantially improved predictions by exploiting the high spatial density of observations TOMS provides. Copyright © 2006 John Wiley & Sons, Ltd.

Eddy meridional ozone transport in Antarctica in August–October 1998 and 2002

A strong zonal circulation, with a well‐isolated polar vortex that resulted in one of the largest recorded ozone holes, characterized the austral winter–spring of 1998. In contrast, in 2002 intensive vacillation of the zonal circulation, a disturbed and weakened polar vortex and record high planetary wave activity followed by major stratospheric warming in late September led to splitting of the polar vortex and to the smallest ozone hole observed over the past 20 years or more. Variability of total ozone column in the southern extratropics during August–October 1998 and 2002 and eddy meridional ozone transport induced by planetary waves activity were investigated. Unprecedented high activity of planetary waves caused significantly stronger poleward eddy ozone transport in 2002, with a maximum in the middle stratosphere at the time of major stratospheric warming. The role of poleward ozone transport in the observed shallow ozone hole in 2002 is discussed.