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

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 dif- ference 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 oscilla- tions 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. Tropi- cal TCO shows high concentration during the westerly phase and low concentration during the easterly phase of the equatorial stratospheric quasi-biennial oscillation.
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Assessing the impact of clouds on ground-based UV–visible total column ozone measurements in the high Arctic

Assessing the impact of clouds on ground-based UV–visible total column ozone measurements in the high Arctic

Abstract. Zenith-Sky scattered light Differential Optical Ab- sorption Spectroscopy (ZS-DOAS) has been used widely to retrieve total column ozone (TCO). ZS-DOAS measure- ments have the advantage of being less sensitive to clouds than direct-sun measurements. However, the presence of clouds still affects the quality of ZS-DOAS TCO. Clouds are thought to be the largest contributor to random uncertainty in ZS-DOAS TCO, but their impact on data quality still needs to be quantified. This study has two goals: (1) to investigate whether clouds have a significant impact on ZS-DOAS TCO, and (2) to develop a cloud-screening algorithm to improve ZS-DOAS measurements in the Arctic under cloudy condi- tions. To quantify the impact of weather, 8 years of measured and modelled TCO have been used, along with informa- tion about weather conditions at Eureka, Canada (80.05 ◦ N, 86.41 ◦ W). Relative to direct-sun TCO measurements by Brewer spectrophotometers and modelled TCO, a positive bias is found in ZS-DOAS TCO measured in cloudy weather, and a negative bias is found for clear conditions, with dif- ferences of up to 5 % between clear and cloudy conditions. A cloud-screening algorithm is developed for high latitudes using the colour index calculated from ZS-DOAS spectra. The quality of ZS-DOAS TCO datasets is assessed using a statistical uncertainty estimation model, which suggests a 3 %–4 % random uncertainty. The new cloud-screening al-
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Efficient prediction of total column ozone based on support vector regression algorithms, numerical models and Suomi-satellite data

Efficient prediction of total column ozone based on support vector regression algorithms, numerical models and Suomi-satellite data

The prediction of total column ozone (TCO) is a difficult problem with important environmental applications. In this paper, a novel and efficient prediction method for TCO has been proposed, which includes an excellent performance regression approach (SVR) applied to a set of predictive vari- ables from heterogeneous sources, such as satellite data (Suomi NPP polar satellite), numerical models (GFS) or direct measurements using devices such as sunphotometers. Data from satellite instruments consist of temperature and humidity profiles at different heights, and TCO measurements from the days before the prediction. The GFS model provides predictions of temperature and humidity for the day
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Effects of Sudden Stratospheric Warming Events on the Distribution of Total Column Ozone over Polar and Middle Latitude Regions

Effects of Sudden Stratospheric Warming Events on the Distribution of Total Column Ozone over Polar and Middle Latitude Regions

In this study, the variation of total ozone concentration during five SSWs cases (1998-99, 1987-88, 1984-85, 1981-82 and 1979-80) was analyzed over the polar and middle latitude regions. Warming in the polar stratos- phere occurred in the mid-winter resulted in an increase of 30 DU in the TCO mean value. On the other hand the final stratospheric warming, which occurred in the late winter (e.g. SSW 1979-80) shows grater values of TCO variation (greater than 50 DU). But in the middle latitude region the variability of TCO is about 10 DU from the mean value and this may be attributed to dynamical reasons than the chemical aspects. Total ozone concentra- tion increases over the polar region with a lag of 2 days after the reversal of the meridional temperature gradient. Total column ozone shows a positive correlation with the temperature at the polar region and a negative correla- tion over the middle latitude region. From the analysis it may be concluded that the variability in ozone concen- tration over the polar region is connected with dynamical behavior and heterogeneous photochemistry. But in middle latitude region ozone variation may be due to dynamical changes than due to other factors. The impact of SSW is very important and it alters the chemical and dynamical characteristics of the polar weather and it also modifies the low latitude weather systems through high and low latitude interactions.
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Temporal Distribution of Total Column Ozone over Cochin—A Study Based on in Situ Measurements and ECMWF Reanalysis

Temporal Distribution of Total Column Ozone over Cochin—A Study Based on in Situ Measurements and ECMWF Reanalysis

The study of temporal distribution of ozone is very important for understanding the atmospheric chemistry and thereby its impact on environment, weather and climate. The whole stratospheric chemistry is controlled by the ozone layer and it plays a key role in maintaining the earth-atmosphere radiative equilibrium. The maximum concentration of ozone is found in the stratosphere (90%), and the remaining 10% in the troposphere. Stratos- pheric ozone is essential for sustaining life on earth, whereas tropospheric ozone is a greenhouse gas [1] [2]. The net ozone production in a pure oxygen atmosphere is determined by the Chapman cycle. Tropospheric ozone is mainly produced due to the chemical reactions of pollutants and it is harmful to health. Hence the ozone which is in the stratosphere is termed as good ozone and that in the troposphere is known as bad ozone. Total column ozone at any location on the globe is found by measuring all the ozone in the atmosphere directly above that lo- cation. Total ozone present in the stratosphere and troposphere is expressed in Dobson Unit (DU). Higher values (~300 DU - 500 DU) of ozone are present in the polar stratosphere and lower values (~250 DU - 280 DU) in the tropical stratosphere. Majority of the ozone molecules are produced in the tropical upper stratospheric region where the exposure of sunlight is high. It is widely appreciated that the dynamics of the stratosphere is interre- lated to a good extent with that of the troposphere [3] [4]. Thus transport and wind motion in the stratosphere are interconnected with that of the troposphere and thus play crucial role in ozone distribution over the tropics. Even though ozone is produced in the tropical upper stratosphere, it is being transported to higher latitudes and poles by Brewer Dobson Circulation.
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OMI total column ozone: extending the long-term data record

OMI total column ozone: extending the long-term data record

Abstract. The ozone data record from the Ozone Monitor- ing Instrument (OMI) onboard the NASA Earth Observing System (EOS) Aura satellite has proven to be very stable over the 10-plus years of operation. The OMI total column ozone processed through the Total Ozone Mapping Spec- trometer (TOMS) ozone retrieval algorithm (version 8.5) has been compared with ground-based measurements and with ozone from a series of SBUV/2 (Solar Backscatter Ultravi- olet) instruments. Comparison with an ensemble of Brewer– Dobson sites shows an absolute offset of about 1.5 % and almost no relative trend. Comparison with a merged ozone data set (MOD) created by combining data from a series of SBUV/2 instruments again shows an offset, of about 1 %, and a relative trend of less than 0.5 % over 10 years. The offset is mostly due to the use of the old Bass–Paur ozone cross sections in the OMI retrievals rather than the Brion– Daumont–Malicet cross sections that are now recommended. The bias in the Southern Hemisphere is smaller than that in the Northern Hemisphere, 0.9 % vs. 1.5 %, for reasons that are not completely understood. When OMI was compared with the European realization of a multi-instrument ozone time series, the GTO (GOME type Total Ozone) data set, there was a small trend of about − 0.85 % decade −1 . Since all the comparisons of OMI relative to other ozone measuring systems show relative trends that are less than 1 % decade −1 , we conclude that the OMI total column ozone data are suffi- ciently stable that they can be used in studies of ozone trends.
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TREND ANALYSIS OF TOTAL COLUMN OZONE OVER INDIA USING TOMS DATA FROM 1979 TO 2010

TREND ANALYSIS OF TOTAL COLUMN OZONE OVER INDIA USING TOMS DATA FROM 1979 TO 2010

Figure 2 represents the percentage of total column ozone (TCO) anomaly from 1979 to 2010. The data are deseasonalized by estimating the deviation from monthly mean. TCO over all the twelve stations is found varying from 210DU to 380DU. A decreasing trend is observed for all the stations. Slopes of the trend line lie between 0.004 and 0.008 indicating a stable trend. However, high declining rate over Northern India was reported during 1997-2003 [Sahoo et al., 2005].

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

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 repre- sentative 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 Ul- traviolet 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 dis- cuss 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 observa- tions and their relative uncertainty, to calculate an improved estimate of the daily mean total column ozone. It is demon- strated that this method can increase the number of contribut- ing 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 tradi- tional direct sun vs. zenith sky average choice. To comple- ment the new calculation of a best representative value of to- tal 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.
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Intercomparison of total column ozone data from the Pandora spectrophotometer with Dobson, Brewer, and OMI measurements over Seoul, Korea

Intercomparison of total column ozone data from the Pandora spectrophotometer with Dobson, Brewer, and OMI measurements over Seoul, Korea

Abstract. Daily total column ozone (TCO) measured us- ing the Pandora spectrophotometer (no. 19) was compared with data from the Dobson (no. 124) and Brewer (no. 148) spectrophotometers, as well as from the Ozone Monitor- ing Instrument (OMI) (with two different algorithms, To- tal Ozone Mapping Spectrometer (TOMS) TOMS and dif- ferential optical absorption spectroscopy (DOAS) methods), over the 2-year period between March 2012 and March 2014 at Yonsei University, Seoul, Korea. Based on the linear- regression method, the TCO from Pandora is closely corre- lated with those from other instruments with regression coef- ficients (slopes) of 0.95 (Dobson), 1.00 (Brewer), 0.98 (OMI- TOMS), and 0.97 (OMI-DOAS), and determination coeffi- cients (R2) of 0.95 (Dobson), 0.97 (Brewer), 0.96 (OMI- TOMS), and 0.95 (OMI-DOAS). The daily averaged TCO from Pandora has within 3 % differences compared to TCO values from other instruments. For the Dobson measure- ments in particular, the difference caused by the inconsis- tency in observation times when compared with the Pandora measurements was up to 12.5 % because of diurnal variations in the TCO values. However, the comparison with Brewer after matching the observation time shows agreement with large R 2 and small biases. The TCO ratio between Brewer and Pandora shows the 0.98 ± 0.03, and the distributions for
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Ozone layer adaptive model from direct relationship between solar activity and total column ozone for the tropical equator-Andes-Colombian region

Ozone layer adaptive model from direct relationship between solar activity and total column ozone for the tropical equator-Andes-Colombian region

Due to the lack of models to predict the ozone layer even after an ample range of total column ozone (TCO) measurements around the globe, a direct relationship between solar activity by means of sunspot number obser- vations and total ozone satellite data for a tropical Andes mountains region at Bogotá-Colombia, is presented. Sunspot number data and 37 years of TCO records from satellite missions Nimbus 7, Meteor 3, Earth Probe and AURA from January 1979 through August 2016, are analyzed. Ozone annual cyclic behavior, which strongly depends on the annual cyclic Sun-Earth distance variation, as well as the dynamics of the solar activity cycles allow to derive a physical-mathematical adaptive model for predicting and reconstructing daily stratospheric ozone over the city of Bogotá, very close to the equator. Results suggest that the ozone layer as a natural indi- cator of solar activity.
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Global and Hemispherical Interannual Variation of Total Column Ozone from TOMS and OMI Data

Global and Hemispherical Interannual Variation of Total Column Ozone from TOMS and OMI Data

Daily Total Column Ozone (TCO) measurements compiled from Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instruments (OMI) were used to analyze the global and hemispherical TCO interannual varia- tions. Two periods of TCO measurements were analyzed separately covering full years. For the 1978-1994 period, the TCO showed a global decade de- crease rate of 13.45 DU (about −4.3%). For the Northern Hemisphere(NH) the decade decrease rate was of 12.96 DU (−4.0%), while in the Southern He- misphere (SH) was of 13.57 DU (−4.5%). These decreases in ozone trends, using the totality of TOMS and OMI satellite measurements, are greater than those reported in literature. The 1998-2014 period global TCO decade de- crease rate was of 1.56 DU, corresponding 0.94 DU and 0.138 DU for the NH and SH, respectively. The global TCO variations must show a double annual periodicity, the first one with maxima in March due to the Northern Hemis- phere (NH) and the second one during September due to the Southern He- misphere (SH). However, the maxima due to SH TCO interannual variations have gradually vanished. A disturbance in the SH TCO interannual variations has appeared since 1980; graphically the periodicity brakes down and trans- forms to a double peak from 1985 and on. This effect can be attributed to the hemispheric impact of the ozone hole at the South Pole. Between October 1, 2004 and December 14, 2005 TOMS and OMI have recorded this disturbance unequivocally. We conclude that the disturbance in SH TCO has an irreversi- ble character.
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A Comparative Study of Intra Seasonal Variability of Total Column Ozone Measured over the Tropical Maritime and Coastal Stations Using Microtop II Ozonometer

A Comparative Study of Intra Seasonal Variability of Total Column Ozone Measured over the Tropical Maritime and Coastal Stations Using Microtop II Ozonometer

(GAW) programme of the World Meteorological Organisation (WMO) employs various total ozone measuring instruments, among them the Dobson Spectro- meter, originally developed in the 1920s, then modern, automated Brewer Spec- trometer, available since the early 1980s have shown their reliability and accura- cy in the long-term ground measurements of total column ozone. The disadvan- tage of the spectrometer is their high price, high cost of operation and mainten- ance and large size and weight, which is adverse for field campaigns. Well trained staff requires to achieve good results and to keep the instruments well calibrated over a long time of operation. These reasons have prevented popular- ity of the spectrometer for ozone measurements especially in developing coun- tries, which cannot afford the high instrumental and personal expenses. The recent development of a small, inexpensive, hand-held filter Ozonometer such as the MICROTOPS by Solar Light Co. accelerated the total ozone measurements worldwide with less expense, accurate with WMO standard [29]. The Compara- tive study of TCO measurements using Microtop II Ozonometer with other ground-based spectrometer measurements and satellite observations are already available for the reference [30] [31]. The present paper is based only on the in-situ measurements of TCO using Microtop II Ozonometer and the compari- son with satellite and reanalysis TCO were already discussed in the previous study [28].
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Trend of total column ozone over Mexico from TOMS and OMI data (1978-2013)

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 surpris- ingly 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.
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Climate warming and decreasing total column ozone over the Tibetan Plateau during winter and spring

Climate warming and decreasing total column ozone over the Tibetan Plateau during winter and spring

The asymmetric responses of the northern and southern stratosphere to SST meridional gradient changes and dif- ferent stratospheric temperature and zonal wind responses among the three runs may also have been related to dif- ferent wave properties and wave propagation. Limpasuvan and Hartmann (2000) pointed out that high frequency tran- sient waves contribute to the majority of total eddy forcing in the SH, while stationary waves control the eddy momentum fluxes in the NH. It is known that stationary waves are due to asymmetries at the Earth’s surface, i.e., mountains, contrast- ing land–sea distributions, and SST asymmetries (e.g., Huang and Gambo, 1982). Therefore, it can be expected that SST in- creases of any type, as depicted in Fig. 1, will cause changes in the strength of stationary waves in the NH due to changes in land–sea surface temperature contrasts. Therefore, it is likely that the NH polar vortex is more sensitive to SST in- creases than the SH polar vortex, as can also be supported by Fig. 2, which shows that the northern polar stratosphere was warmed in all the three runs. In the SH, where the land–sea contrast is not dominant, the wave strength is expected to be more sensitive to magnitudes of SST changes. Note that the magnitude of SST increases was the largest in E2 and small- est in E4; therefore, the temperature response in the southern polar stratosphere was the largest and most significant in E2 (see Fig. 2). To provide more information on the effects of different SST changes on wave activities, Fig. 7 shows the differences in eddy heat flux (v T ) between different runs. The eddy heat flux is proportional to the vertical flux of wave activity via the EP flux (Dunkerton et al., 1981, Weber et al., 2003). Figure 7 indicates enhancements in planetary wave activities in the high-latitude troposphere in E2, E3 and E4. A slight enhancement of wave flux in the tropical and sub- tropical troposphere was also evident. The result here is con- sistent with Shepherd and McLandress (2011), who showed that the strengthening of the upper flanks of the subtropical jets allows more waves to penetrate into the subtropical LS. The eddy heat flux changes in the NH caused by the SST increases were overall larger than in the SH. As mentioned earlier, the wave strength is expected to be more sensitive to magnitudes of SST changes in the SH. Figure 7 indeed shows that a global uniform 1.0 K SST increase caused the largest eddy heat flux changes in the SH, while the gradient SST in- creases between 60 ◦ N–60 ◦ S caused relatively smaller eddy heat flux changes.
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On the compatibility of Brewer total column ozone measurements in two adjacent valleys (Arosa and Davos) in the Swiss Alps

On the compatibility of Brewer total column ozone measurements in two adjacent valleys (Arosa and Davos) in the Swiss Alps

sured ozone column (Scarnato et al., 2009; Petropavlovskikh et al., 2011; Christodoulakis et al., 2015). This effect partic- ularly concerns Dobson and single-monochromator Brewer instruments located at high latitude and it varies from in- strument to instrument (Karppinen et al., 2015). To reduce these interferences in this study, the observations were lim- ited to air mass values µ ≤ 4, which corresponds to a SC of ∼ 1200 DU for the typical ∼ 300 DU ozone column of Arosa. To further analyze the stray-light potential influence, the seasonality of the SC distribution averaged over the pe- riod 2011–2017 was calculated as illustrated in Fig. 7. From April to October the SC was below 800 for 90 % of the data, which were essentially free of the stray-light effect as is the case for most of the Brewer instruments. Contrarily, mea- surements in December and January showed SC values above 800 which may potentially have induced a low ozone column bias for the two single-monochromator instruments, B 040 and
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SPECTRAL ANALYSIS AND FORECAST OF OZONE OVER EGYPT

SPECTRAL ANALYSIS AND FORECAST OF OZONE OVER EGYPT

In this paper the relationships between total ozone amount and meteorological variables have been deduced for eight stations of Egypt. Residual method has been applied to estimate total column ozone (TCO) values using the meteorological variables. Empirical equations relating TCO with these variables have been deduced for the eight stations. Very good correlation coefficient between the actual and estimated values of ozone has been found. The obtained good relations make us able to estimate and forecast ozone amount whether there are meteorological stations or not, by using numerical weather prediction models outputs. Spectral analysis of the daily, monthly and annual values of TCO data of the eight stations has been examined. It is found that the annual wave is the dominant wave in all stations. This wave simply represents the seasonal variation caused due to meridional circulation. There are five significant dominant waves appear in the annual time series of the most stations, the wave length of these waves are 2.8, 2.6, 4.5, 18 and 9 year respectively. The first and second waves are qualitatively matches the quasi-biennial oscillation. The last wave which has a period of approximately 9 years clearly matches the solar sunspot cycle period, while the wave 4.5 year cycle seem to be associated with the El- Nino Southern Oscillation.
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Total ozone mass calculation to assess the global ozone behavior

Total ozone mass calculation to assess the global ozone behavior

Ozone trends have been analyzed by diverse methods in many local and regional studies over various time peri- ods. Few studies have moved beyond the total column ozone (TCO) analysis to quantify the total amount of ozone in the atmosphere, and analyzing its seasonal variations and interannual trends. Dave and Mateer (1967) conducted a preliminary study of the feasi- bility of determining total atmospheric ozone from satellite measurements. Bodeker et al. (2001) noted that global ozone mass levels were aproximately 3 × 10 12 kg.
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Estimates of Ozone Return Dates from Chemistry-Climate Model Initiative Simulations

Estimates of Ozone Return Dates from Chemistry-Climate Model Initiative Simulations

Figure S8. Estimated MMM1S return dates (red triangles) of total column ozone from the SEN-C2-fGHG, SEN-C2-fN2O, SEN-C2-fCH4 and SEN-C2-CH4RCP85 simulations for different latitude bands. The estimated 1-σ uncertainties are shown with vertical black lines. Estimates for individual models are shown with coloured dots. Some individual models do not predict a return of column ozone in the tropics. Return dates from REF-C2 (see Figure 4 in main paper) are shown with grey triangles.

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Single Scattering Albedo’s Spectral Dependence Effect on UV Irradiance

Single Scattering Albedo’s Spectral Dependence Effect on UV Irradiance

in the UV-B part (290-315 nm) of the spectrum at 0.5 nm intervals. For total column ozone measurements, the instrument is designed to take direct sun measurements at five nominal wavelengths 306.3, 310.1, 313.5, 316.8 and 320.0 nm which are used with the standard algorithm to retrieve columnar ozone measurements from Brewer spectrophotometers [41]. Brewer ozone data for Athens have been analysed in recent studies [42,43]. In addition, the instrument was used to derive AOD in the visible part of the solar spectrum [44]. In this study, we analyse for the first time spectral UV irradiance measurements at 324 nm from the Athens Brewer instrument, for the period January 2009 to December 2014. The Brewer spectroradiometer is calibrated regularly by means of a standard radiometer of the same type. The last three calibrations were performed at the Academy of Athens in July 2007, October 2010 and October 2013 by the travelling standard Brewer #017 (International Ozone Services Inc., Mr. Ken Lamb and Dr. Volodya Savastiouk).
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Trend quality ozone from NPP OMPS: the version 2 processing

Trend quality ozone from NPP OMPS: the version 2 processing

Abstract. A version 2 processing of data from two ozone monitoring instruments on Suomi NPP, the OMPS nadir ozone mapper and the OMPS nadir ozone profiler, has now been completed. The previously released data were useful for many purposes but were not suitable for use in ozone trend analysis. In this processing, instrument artifacts have been identified and corrected, an improved scattered light correc- tion and wavelength registration have been applied, and soft calibration techniques were implemented to produce a cali- bration consistent with data from the series of SBUV/2 in- struments. The result is a high-quality ozone time series suit- able for trend analysis. Total column ozone data from the OMPS nadir mapper now agree with data from the SBUV/2 instrument on NOAA 19 with a zonal average bias of −0.2 % over the 60 ◦ S to 60 ◦ N latitude zone. Differences are some-
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