scholarly journals Validation of the Aura Ozone Monitoring Instrument total column ozone product

2008 ◽  
Vol 113 (D15) ◽  
Author(s):  
R. McPeters ◽  
M. Kroon ◽  
G. Labow ◽  
E. Brinksma ◽  
D. Balis ◽  
...  
Keyword(s):  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
Monitoring Instrument ◽  
Ozone Monitoring ◽  
Column Ozone ◽  
Total Column

scholarly journals Monitoring and assimilation tests with TROPOMI data in the CAMS system: near-real-time total column ozone

2019 ◽  
Vol 19 (6) ◽  
pp. 3939-3962 ◽  
Author(s):  
Antje Inness ◽  
Johannes Flemming ◽  
Klaus-Peter Heue ◽  
Christophe Lerot ◽  
Diego Loyola ◽  
...  
Keyword(s):  
Real Time ◽  
Positive Impact ◽  
Atmospheric Composition ◽  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
Monitoring Instrument ◽  
Ozone Monitoring ◽  
Column Ozone ◽  
The Impact ◽  
Total Column

Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel-5 Precursor (S5P) satellite launched in October 2017 yields a wealth of atmospheric composition data, including retrievals of total column ozone (TCO3) that are provided in near-real-time (NRT) and off-line. The NRT TCO3 retrievals (v1.0.0–v1.1.2) have been included in the data assimilation system of the Copernicus Atmosphere Monitoring Service (CAMS), and tests to monitor the data and to carry out first assimilation experiments with them have been performed for the period 26 November 2017 to 30 November 2018. The TROPOMI TCO3 data agree to within 2 % with the CAMS analysis over large parts of the globe between 60∘ N and 60∘ S and also with TCO3 retrievals from the Ozone Monitoring Instrument (OMI) and the Global Ozone Monitoring Experiment-2 (GOME-2) that are routinely assimilated by CAMS. However, the TCO3 NRT data from TROPOMI show some retrieval anomalies at high latitudes, at low solar elevations and over snow/ice (e.g. Antarctica and snow-covered land areas in the Northern Hemisphere), where the differences with the CAMS analysis and the other data sets are larger. These differences are particularly pronounced over land in the NH during winter and spring (when they can reach up to 40 DU) and come mainly from the surface albedo climatology that is used in the NRT TROPOMI TCO3 retrieval. This climatology has a coarser horizontal resolution than the TROPOMI TCO3 data, which leads to problems in areas where there are large changes in reflectivity from pixel to pixel, e.g. pixels covered by snow/ice or not. The differences between TROPOMI and the CAMS analysis also show some dependency on scan position. The assimilation of TROPOMI TCO3 has been tested in the CAMS system for data between 60∘ N and 60∘ S and for solar elevations greater than 10∘ and is found to have a small positive impact on the ozone analysis compared to Brewer TCO3 data and an improved fit to ozone sondes in the tropical troposphere and to IAGOS aircraft profiles at West African airports. The impact of the TROPOMI data is relatively small because the CAMS analysis is already well constrained by several other ozone retrievals that are routinely assimilated. When averaged over the periods February–April and September–October 2018, differences between experiments with and without assimilation of TROPOMI data are less than 2 % for TCO3 and less than 3 % in the vertical for seasonal mean zonal mean O3 mixing ratios, with the largest relative differences found in the troposphere.

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

2016 ◽  
Author(s):  
Jiyoung Kim ◽  
Jhoon Kim ◽  
Hi-Ku Cho ◽  
Jay Herman ◽  
Sang Seo Park ◽  
...  
Keyword(s):  
Optical Absorption Spectroscopy ◽  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
Monitoring Instrument ◽  
Ozone Monitoring ◽  
The Difference ◽  
Column Ozone ◽  
Observation Times ◽  
Total Column ◽  
Daily Total

Abstract. Daily total column ozone (TCO) measured using the Pandora spectrophotometer (#19) was intercompared with data from the Dobson (#124) and Brewer (#148) spectrophotometers, as well as from the Ozone Monitoring Instrument (OMI), over the 2-year period between March 2012 and March 2014 at Yonsei University, Seoul, Korea. The Pandora TCO measurements are closely correlated with those from the Dobson, Brewer, and OMI instruments with regression coefficients (slopes) of 0.95, 1.00, 0.98 (OMI-TOMS), and 0.97 (OMI-DOAS), respectively, and determination coefficients (R2) of 0.95, 0.97, 0.96 (OMI-TOMS), and 0.95 (OMI-DOAS), respectively. In particular, they show a close agreement with the Brewer TCO measurements, with slope and R2 values of 1.00 and 0.97, respectively. The difference between the Pandora and Dobson data can be explained by smaller amount of Dobson data available to calculate the daily averages, observation times, solar zenith angles, SO2 effect, temperature, and humidity between the two datasets. The difference in the results obtained from the Pandora instrument and Ozone Monitoring Instrument-Differential Optical Absorption Spectroscopy (OMI-DOAS algorithm) can be explained by the dependence on seasonal variations of about ± 2 % and solar zenith angle leading to overestimation by 5 % of OMI-DOAS measurements. For the Dobson measurements in particular, the difference caused by the inconsistency in observation times when compared with the Pandora measurements was up to 12.5 % on 22 June 2013 because of diurnal variations in the TCO values. However, despite these various differences and discrepancies, the daily TCO values measured by the four instruments during the 2-year study period are accurate and closely correlated.

scholarly journals Comparison of UV irradiances from Aura/Ozone Monitoring Instrument (OMI) with Brewer measurements at El Arenosillo (Spain) – Part 1: Analysis of parameter influence

2010 ◽  
Vol 10 (3) ◽  
pp. 6797-6827 ◽  
Author(s):  
M. Antón ◽  
V. E. Cachorro ◽  
J. M. Vilaplana ◽  
C. Toledano ◽  
N. A. Krotkov ◽  
...  
Keyword(s):  
Companion Paper ◽  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
Monitoring Instrument ◽  
Solar Elevation ◽  
Uv Irradiance ◽  
Ozone Monitoring ◽  
Absorbing Aerosols ◽  
Column Ozone ◽  
Sky Conditions

Abstract. The main objective of this study is to compare the erythemal UV irradiance (UVER) and spectral UV irradiances (at 305, 310 and 324 nm) from Ozone Monitoring Instrument (OMI) onboard NASA EOS/Aura polar sun-synchronous satellite (launched in July 2004, local equator crossing time 01:45 p.m.) with ground-based measurements from the Brewer spectroradiometer #150 located at El Arenosillo (South of Spain). The analyzed period comprises more than four years, from October 2004 to December 2008. The effects of several factors (clouds, aerosols, ozone and the solar elevation) on OMI-Brewer comparisons were analyzed. The proxies used for each factor were: OMI Lambertian Equivalent Reflectivity (LER) at 360 nm (clouds), the Aerosol Optical Depth (AOD) at 440 nm measured from the ground-based Cimel sun-photometer (http://aeronet.gsfc.nasa.gov), OMI total column ozone, and solar elevation at OMI overpass time. The comparison for all sky conditions reveals positive biases (OMI higher than Brewer) 12.3% for UVER, 14.2% for UV irradiance at 305 nm, 10.6% for 310 nm and 8.7% for 324 nm. The OMI-Brewer Root Mean Square Error (RMSE) is reduced when cloudy cases are removed from the analysis, (e.g., RMSE ~20% for all sky conditions and RMSE smaller than 10% for cloud-free conditions). However, the biases remain and even become more significant for the cloud-free cases with respect to all sky conditions. The mentioned overestimation is clearly documented as due to aerosol extinction influence. The differences OMI-Brewer typically decrease with increasing the Solar Zenith Angle (SZA). The seasonal dependence of the OMI-Brewer difference for cloud-free conditions is driven by aerosol climatology. To account for the aerosol effect, a first evaluation in order to compare with previous TOMS results (Anton et al., 2007) was performed. This comparison shows that the OMI bias is between +14% and +19% for UVER and spectral UV irradiances for moderately-high aerosol load (AOD>0.25). The OMI bias is decreased by a factor of 2 (the typical bias varies from +8% to +12%) under cloud-free and low aerosol load conditions (AOD<0.1). More detailed analysis of absorbing aerosols influence on OMI bias at our station is presented in a companion paper (Cachorro et al., 2010).

scholarly journals An assessment of Ozone Mini-holes Representation in Reanalyses Over the Northern Hemisphere

2017 ◽  
Author(s):  
Luis Millan ◽  
Gloria Manney
Keyword(s):  
Seasonal Variability ◽  
Synoptic Scale ◽  
Hole Formation ◽  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
Ozone Profile ◽  
Ozone Monitoring ◽  
Column Ozone ◽  
Hole Number ◽  
Total Column

Abstract. An ozone mini-hole is a synoptic-scale region with strongly decreased total column ozone resulting from dynamical processes. Using total column measurements from the Ozone Monitoring Instrument and ozone profile measurements from the Microwave Limb Sounder, we evaluate the accuracy of mini-hole representation in five reanalyses. This study provides a metric of the reanalyses’ ability to capture dynamically-driven ozone variability. The reanalyses and the measurements show similar seasonal variability and geographical distributions of mini-holes; however, all of the reanalyses underestimate the number of mini-holes, their area, and in many reanalyses their location displays an eastward bias. The reanalyses’ underestimation of mini-hole number ranges from about 34 % to about 83 %. The mini-hole vertical representation in the reanalyses agrees well with that in the MLS measurements and, furthermore, is consistent with previously reported mechanisms for mini-hole formation. The skill of the reanalyses is not closely tied to the ozone fields assimilated, suggesting that the dynamics of the reanalysis models are more important than the assimilated ozone fields to reproducing ozone mini-holes.

scholarly journals An assessment of ozone mini-hole representation in reanalyses over the Northern Hemisphere

2017 ◽  
Vol 17 (15) ◽  
pp. 9277-9289 ◽  
Author(s):  
Luis F. Millán ◽  
Gloria L. Manney
Keyword(s):  
Seasonal Variability ◽  
Synoptic Scale ◽  
Hole Formation ◽  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
Ozone Profile ◽  
Ozone Monitoring ◽  
Column Ozone ◽  
Hole Number ◽  
Total Column

Abstract. An ozone mini-hole is a synoptic-scale region with strongly decreased total column ozone resulting from dynamical processes. Using total column measurements from the Ozone Monitoring Instrument and ozone profile measurements from the Microwave Limb Sounder, we evaluate the accuracy of mini-hole representation in five reanalyses. This study provides a metric of the reanalyses' ability to capture dynamically driven ozone variability. The reanalyses and the measurements show similar seasonal variability and geographical distributions of mini-holes; however, all of the reanalyses underestimate the number of mini-holes and their area, and in many reanalyses their location displays an eastward bias. The reanalyses' underestimation of mini-hole number ranges from about 34 to about 83 %. The mini-hole vertical representation in the reanalyses agrees well with that in the MLS measurements and, furthermore, is consistent with previously reported mechanisms for mini-hole formation. The skill of the reanalyses is not closely tied to the ozone fields assimilated, suggesting that the dynamics of the reanalysis models are more important than the assimilated ozone fields to reproducing ozone mini-holes.

scholarly journals Monitoring and assimilation tests with TROPOMI data in the CAMS system. Part 1: Near-real time total column ozone

2018 ◽  
Author(s):  
Antje Inness ◽  
Johannes Flemming ◽  
Klaus-Peter Heue ◽  
Christophe Lerot ◽  
Diego Loyola ◽  
...  
Keyword(s):  
Real Time ◽  
Early Stage ◽  
The Other ◽  
Atmospheric Composition ◽  
Observation System ◽  
Total Column Ozone ◽  
Monitoring Instrument ◽  
Ozone Monitoring ◽  
Column Ozone ◽  
Total Column

Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel 5 Precursor (S5P) satellite launched in October 2017 yields a wealth of atmospheric composition data, including retrievals of total column ozone (TCO3) that are provided in near-real time (NRT) and off-line. These NRT TCO3 retrievals (V1.0.0) have been included in the data assimilation system of the Copernicus Atmosphere Monitoring Service (CAMS), and tests to monitor the data and to carry out first assimilation experiments with them have been performed for the period 26 November 2017 to 3 May 2018. TROPOMI was still in its commissioning phase until 24 April 2018. Nevertheless, the results show that, even at this early stage, the TROPOMI TCO3 data generally agree well with the CAMS analysis over large parts of the Globe and also with TCO3 retrievals from the Ozone Monitoring Instrument (OMI) and the Global Ozone Monitoring Experiment-2 (GOME-2) that are routinely assimilated by CAMS. However, the TCO3 NRT data from TROPOMI show some retrieval anomalies at high latitudes, at low solar elevations and over snow/ice (e.g. Antarctica) where the differences with the CAMS analysis and the other datasets are larger. These differences come mainly from the surface albedo climatology that is used in the NRT TROPOMI TCO3 retrieval. This climatology has a coarser horizontal resolution than the TROPOMI TCO3 data which leads to problems in areas where there are large changes in reflectivity from pixel to pixel, e.g. pixels covered by snow/ice or not. The assimilation of TROPOMI TCO3 has been tested in the CAMS system for data between 60° N and 60° S and for solar elevations less than 10° and is found to have only little impact on the ozone analysis, because the CAMS analysis is already well constrained by several other ozone retrievals that are routinely assimilated. Variational bias correction is applied to the TROPOMI NRT TCO3 data and successfully corrects for the biases seen in the data. Averaged over the period 26 November 2017 to 3 May 2018, difference between experiments with and without assimilation of TROPOMI data are less than 2 % for TCO3 and less than 1 % in the vertical for averaged zonal mean O3 mixing ratios. Compared to independent observation (Brewer spectrometers, ozone sondes, IAGOS ozone profiles and GAW surface measurements) the differences between the assimilation run and a run without TROPOMI assimilation are also small. The only noteworthy differences between the experiment with and without assimilation of TROPOMI data are seen compared to IAGOS profiles at West African airports where the assimilation of TROPOMI improves the fit of the CAMS analysis to the independent data. Despite the small impact of TROPOMI TCO3 in the CAMS analysis it will be beneficial to include the TROPOMI TCO3 NRT data actively in the operational NRT CAMS analysis after more tests. This will add some redundancy and resilience in the system and will allow us to use a more robust observation system in case some of the other older instruments, whose retrievals are currently assimilated by CAMS, stop working.

scholarly journals The world Brewer reference triad – updated performance assessment and new double triad

2021 ◽  
Vol 14 (3) ◽  
pp. 2261-2283
Author(s):  
Xiaoyi Zhao ◽  
Vitali Fioletov ◽  
Michael Brohart ◽  
Volodya Savastiouk ◽  
Ihab Abboud ◽  
...  
Keyword(s):  
Stratospheric Ozone ◽  
Stray Light ◽  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
Monitoring Instrument ◽  
Long Term Stability ◽  
The World ◽  
Column Ozone ◽  
Modern Era

Abstract. The Brewer ozone spectrophotometer (the Brewer) was designed at Environment and Climate Change Canada (ECCC) in the 1970s to make accurate automated total ozone column measurements. Since the 1980s, the Brewer instrument has become a World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) standard ozone monitoring instrument. Now, more than 230 Brewers have been produced. To assure the quality of the Brewer measurements, a calibration chain is maintained, i.e., first, the reference instruments are independently absolutely calibrated, and then the calibration is transferred from the reference instrument to the travelling standard, and subsequently from the travelling standard to field instruments. ECCC has maintained the world Brewer reference instruments since the 1980s to provide transferable calibration to field instruments at monitoring sites. Three single-monochromator (Mark II) type instruments (serial numbers 008, 014, and 015) formed this world Brewer reference triad (BrT) and started their service in Toronto, Canada, in 1984. In the 1990s, the Mark III type Brewer (known as the double Brewer) was developed, which has two monochromators to reduce the internal instrumental stray light. The double-Brewer world reference triad (BrT-D) was formed in 2013 (serial numbers 145, 187 and 191), co-located with the BrT. The first assessment of the BrT's performance was made in 2005, covering the period between 1984 and 2004 (Fioletov et al., 2005). The current work provides an updated assessment of the BrT's performance (from 1999 to 2019) and the first comprehensive assessment of the BrT-D. The random uncertainties of individual reference instruments are within the WMO/GAW requirement of 1 % (WMO, 2001): 0.49 % and 0.42 % for BrT and BrT-D, respectively, as estimated in this study. The long-term stability of the reference instruments is also evaluated in terms of uncertainties of the key instrument characteristics: the extraterrestrial calibration constant (ETC) and effective ozone absorption coefficients (both having an effect of less than 2 % on total column ozone). Measurements from a ground-based instrument (Pandora spectrometer), satellites (11 datasets, including the most recent high-resolution satellite, TROPOspheric Monitoring Instrument), and reanalysis model (the second Modern-Era Retrospective analysis for Research and Applications, MERRA-2) are used to further assess the performance of world Brewer reference instruments and to provide a context for the requirements of stratospheric ozone observations during the last two decades.

scholarly journals Comparison of total column ozone obtained by the IASI-MetOp satellite with ground-based and OMI satellite observations in the southern tropics and subtropics

2015 ◽  
Vol 33 (9) ◽  
pp. 1135-1146 ◽  
Author(s):  
A. M. Toihir ◽  
H. Bencherif ◽  
V. Sivakumar ◽  
L. El Amraoui ◽  
T. Portafaix ◽  
...  
Keyword(s):  
The Other ◽  
Retrieval Algorithm ◽  
Bias Error ◽  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
European Organization ◽  
Comparison Results ◽  
Column Ozone ◽  
Meteorological Satellite ◽  
Total Column

Abstract. This paper presents comparison results of the total column ozone (TCO) data product over 13 southern tropical and subtropical sites recorded from the Infrared Atmospheric Sounder Interferometer (IASI) onboard the EUMETSAT (European organization for the exploitation of METeorological SATellite) MetOp (Meteorological Operational satellite program) satellite. TCO monthly averages obtained from IASI between June 2008 and December 2012 are compared with collocated TCO measurements from the Ozone Monitoring Instrument (OMI) on the OMI/Aura satellite and the Dobson and SAOZ (Système d'Analyse par Observation Zénithale) ground-based instruments. The results show that IASI displays a positive bias with an average less than 2 % with respect to OMI and Dobson observations, but exhibits a negative bias compared to SAOZ over Bauru with a bias around 2.63 %. There is a good agreement between IASI and the other instruments, especially from 15° S southward where a correlation coefficient higher than 0.87 is found. IASI exhibits a seasonal dependence, with an upward trend in autumn and a downward trend during spring, especially before September 2010. After September 2010, the autumn seasonal bias is considerably reduced due to changes made to the retrieval algorithm of the IASI level 2 (L2) product. The L2 product released after August (L2 O3 version 5 (v5)) matches TCO from the other instruments better compared to version 4 (v4), which was released between June 2008 and August 2010. IASI bias error recorded from September 2010 is estimated to be at 1.5 % with respect to OMI and less than ±1 % with respect to the other ground-based instruments. Thus, the improvement made by O3 L2 version 5 (v5) product compared with version 4 (v4), allows IASI TCO products to be used with confidence to study the distribution and interannual variability of total ozone in the southern tropics and subtropics.

scholarly journals A study on harmonizing total ozone assimilation with multiple sensors

2018 ◽  
Author(s):  
Yves J. Rochon ◽  
Michael Sitwell ◽  
Young-Min Cho
Keyword(s):  
Bias Correction ◽  
Vertical Structure ◽  
Correlation Coefficients ◽  
Short Term ◽  
Total Column Ozone ◽  
Ozone Monitoring ◽  
Mean Differences ◽  
Column Ozone ◽  
The Impact ◽  
Total Column

Abstract. The impact of assimilating total column ozone datasets from single and multiple satellite data sources with and without bias correction has been examined with a version of the Environment and Climate Change Canada variational assimilation and forecasting system. The assimilated and evaluated data sources include the Global Ozone Monitoring Experiment-2 instruments on the MetOp-A and MetOp-B satellites (GOME-2A and GOME-2B), the total column ozone mapping instrument of the Ozone Mapping Profiler Suite (OMPS-NM) on the Suomi National Polar-orbiting Partnership (S-NPP) satellite, and the Ozone Monitoring Instrument (OMI) instrument on the Aura research satellite. Ground-based Brewer and Dobson spectrophotometers, and filter ozonometers, as well as the Solar Backscatter Ultraviolet satellite instrument (SBUV/2), served as independent validation sources for total column ozone. Regional and global mean differences of the OMI-TOMS data with measurements from the three ground-based instrument types for the three evaluated two month periods were found to be within 1 %, except for the polar regions with the largest differences from the comparatively small dataset in Antarctica exceeding 3 %. Values from SBUV/2 summed partial columns were typically larger than OMI-TOMS on average by 0.6 to 1.2 &amp;pm; 0.7 %, with smaller differences than with ground-based over Antarctica. OMI-TOMS was chosen as the reference used in the bias correction instead of the ground-based observations due to OMI’s significantly better spatial and temporal coverage and interest in near-real time assimilation. Bias corrections as a function of latitude and solar zenith angle were performed with a two-week moving window using colocation with OMI-TOMS and three variants of differences with short-term forecasts. These approaches are shown to yield residual biases of less than 1 %, with the rare exceptions associated with bins with less data. These results were compared to a time-independent bias correction estimation that used colocations as a function of ozone effective temperature and solar zenith angle which, for the time period examined, resulted in larger changes in residual biases as a function of time for some cases. Assimilation experiments for the July-August 2014 period show a reduction of global and temporal mean biases for short-term forecasts relative to ground-based Brewer and Dobson data from a maximum of about 2.3 % in the absence of bias correction to less than 0.3 % in size when bias correction is included. Both temporally averaged and time varying mean differences of forecasts with OMI-TOMS are reduced to within 1 % for nearly all cases when bias corrected observations are assimilated for the latitudes where satellite data is present. The impact of bias correction on the standard deviations and anomaly correlation coefficients of forecast differences to OMI-TOMS is noticeable but small compared to the impact of introducing any total column ozone assimilation. The assimilation of total column ozone data can result in some improvement, as well as some deterioration, in the vertical structure of forecasts when comparing to Aura-MLS and ozonesonde profiles. The most significant improvement in the vertical domain from the assimilation of total column ozone alone is seen in the anomaly correlation coefficients in the tropical lower stratosphere, which increases from a minimum of 0.1 to about 0.6. Nonetheless, it is made evident that the quality of the vertical structure is most improved when also assimilating ozone profile data, which only weakly affects the total column short-term forecasts.

scholarly journals A new ENSO index derived from satellite measurements of column ozone

2010 ◽  
Vol 10 (8) ◽  
pp. 3711-3721 ◽  
Author(s):  
J. R. Ziemke ◽  
S. Chandra ◽  
L. D. Oman ◽  
P. K. Bhartia
Keyword(s):  
Climate Models ◽  
Southern Oscillation ◽  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
Enso Events ◽  
Gas Measurements ◽  
Column Ozone ◽  
The Tropics ◽  
Total Column ◽  
Enso Index

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.

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