scholarly journals Improvement of OMI ozone profile retrievals in the upper troposphere and lower stratosphere by the use of a tropopause-based ozone profile climatology

2013 ◽  
Vol 6 (3) ◽  
pp. 4333-4369 ◽  
Author(s):  
J. Bak ◽  
X. Liu ◽  
J. C. Wei ◽  
L. L. Pan ◽  
K. Chance ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Meteorological Data ◽  
A Priori ◽  
Tropopause Height ◽  
Ozone Monitoring Instrument ◽  
Upper Troposphere ◽  
Variable Position ◽  
Ozone Profile ◽  
The Mean ◽  
Standard Deviations

Abstract. Motivated by the need of obtaining a more accurate global ozone distribution in the upper troposphere and lower stratosphere (UTLS), we have investigated the use of a tropopause-based (TB) ozone climatology in ozone profile retrieval from the Ozone Monitoring Instrument (OMI). Due to the limited vertical ozone information in the UTLS region from OMI backscattered ultraviolet radiances, better climatological a priori information is important for improving ozone profile retrievals. We present the new TB climatology and evaluate the result of retrievals against previous work. The improved TB climatology is created using ozonesonde profiles from 1983 through 2008 extended with climatological ozone data above sonde burst altitude (~35 km) with the corresponding temperature profiles used to identify the thermal tropopause. The TB climatology consists of the mean states and 1σ standard deviations every month for each 10° latitude band. Three additional processes are applied in deriving our climatology: (1) using a variable shifting offset to define the TB coordinate, (2) separating ozonesonde profiles into tropical and extratropical regimes based on a threshold of 14 km in the thermal tropopause height, and (3) merging with an existing climatology from 5–10 km above the tropopause. The first process changes the reference of profiles to variable position between local and mean tropopause heights within ±5 km at the tropopause and to the mean tropopause elsewhere. The second helps to preserve characteristics of either tropical or extratropical ozone structures depending on tropopause height, especially in the subtropical region. The third improves the climatology above ozonesonde burst altitudes and in the stratosphere by using climatology derived from many more satellite observations of ozone profiles. With aid from the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) tropopause height, the new climatology and retrieval can better represent the dynamical variability of ozone in the tropopause region. The new retrieval result demonstrates significant improvement of UTLS ozone, especially in the extratropical UTLS, when evaluated using ozonesonde measurements and the meteorological data. The use of TB climatology significantly enhances the spatial consistency and the statistically relationship between ozone and potential vorticity/tropopause height in the extratropical UTLS region. Comparisons with ozonesonde measurements show substantial improvements in both mean biases and their standard deviations over the extratropical lowermost stratosphere and UT. Overall, OMI retrievals with the TB climatology show improved ability in capturing ozone gradients across the tropopause demonstrated by tropical/extratropical ozonesonde measurements.

scholarly journals Improvement of OMI ozone profile retrievals in the upper troposphere and lower stratosphere by the use of a tropopause-based ozone profile climatology

2013 ◽  
Vol 6 (9) ◽  
pp. 2239-2254 ◽  
Author(s):  
J. Bak ◽  
X. Liu ◽  
J. C. Wei ◽  
L. L. Pan ◽  
K. Chance ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Meteorological Data ◽  
A Priori ◽  
Tropopause Height ◽  
Ozone Monitoring Instrument ◽  
Upper Troposphere ◽  
Variable Position ◽  
Ozone Profile ◽  
The Mean ◽  
Standard Deviations

Abstract. Motivated by the need of obtaining a more accurate global ozone distribution in the upper troposphere and lower stratosphere (UTLS), we have investigated the use of a tropopause-based (TB) ozone climatology in ozone profile retrieval from the Ozone Monitoring Instrument (OMI). Due to the limited vertical ozone information in the UTLS region from OMI backscattered ultraviolet radiances, better climatological a priori information is important for improving ozone profile retrievals. We present the new TB climatology and evaluate the result of retrievals against previous work. The TB climatology is created using ozonesonde profiles from 1983 through 2008 extended with climatological ozone data above sonde burst altitude (~35 km) with the corresponding temperature profiles used to identify the thermal tropopause. The TB climatology consists of the mean states and 1σ standard deviations for every month for each 10° latitude band. Compared to the previous TB climatology by Wei et al. (2010), three additional processes are applied in deriving our climatology: (1) using a variable shifting offset to define the TB coordinate, (2) separating ozonesonde profiles into tropical and extratropical regimes based on a threshold of 14 km in the thermal tropopause height, and (3) merging with an existing climatology from 5–10 km above the tropopause. The first process changes the reference of profiles to a variable position between local and mean tropopause heights within ±5 km of the tropopause and to the mean tropopause elsewhere. The second helps to preserve characteristics of either tropical or extratropical ozone structures depending on tropopause height, especially in the subtropical region. The third improves the climatology above ozonesonde burst altitudes and in the stratosphere by using climatology derived from many more satellite observations of ozone profiles. With aid from the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) tropopause height, the new climatology and retrieval can better represent the dynamical variability of ozone in the tropopause region. The new retrieval result demonstrates significant improvement of UTLS ozone, especially in the extratropical UTLS, when evaluated using ozonesonde measurements and the meteorological data. The use of TB climatology significantly enhances the spatial consistency and the statistical relationship between ozone and potential vorticity/tropopause height in the extratropical UTLS region. Comparisons with ozonesonde measurements show substantial improvements in both mean biases and their standard deviations over the extratropical lowermost stratosphere and upper troposphere. Overall, OMI retrievals with the TB climatology show improved ability in capturing ozone gradients across the tropopause found in tropical/extratropical ozonesonde measurements.

scholarly journals Evaluation of ozone profile and tropospheric ozone retrievals from GEMS and OMI spectra

2013 ◽  
Vol 6 (2) ◽  
pp. 239-249 ◽  
Author(s):  
J. Bak ◽  
J. H. Kim ◽  
X. Liu ◽  
K. Chance ◽  
J. Kim
Keyword(s):  
Spectral Resolution ◽  
Tropospheric Ozone ◽  
Stratospheric Ozone ◽  
A Priori ◽  
Ozone Monitoring Instrument ◽  
Satellite Platform ◽  
Ozone Profile ◽  
Retrieval Errors ◽  
Standard Deviations ◽  
Column Ozone

Abstract. South Korea is planning to launch the GEMS (Geostationary Environment Monitoring Spectrometer) instrument into the GeoKOMPSAT (Geostationary Korea Multi-Purpose SATellite) platform in 2018 to monitor tropospheric air pollutants on an hourly basis over East Asia. GEMS will measure backscattered UV radiances covering the 300–500 nm wavelength range with a spectral resolution of 0.6 nm. The main objective of this study is to evaluate ozone profiles and stratospheric column ozone amounts retrieved from simulated GEMS measurements. Ozone Monitoring Instrument (OMI) Level 1B radiances, which have the spectral range 270–500 nm at spectral resolution of 0.42–0.63 nm, are used to simulate the GEMS radiances. An optimal estimation-based ozone profile algorithm is used to retrieve ozone profiles from simulated GEMS radiances. Firstly, we compare the retrieval characteristics (including averaging kernels, degrees of freedom for signal, and retrieval error) derived from the 270–330 nm (OMI) and 300–330 nm (GEMS) wavelength ranges. This comparison shows that the effect of not using measurements below 300 nm on retrieval characteristics in the troposphere is insignificant. However, the stratospheric ozone information in terms of DFS decreases greatly from OMI to GEMS, by a factor of ∼2. The number of the independent pieces of information available from GEMS measurements is estimated to 3 on average in the stratosphere, with associated retrieval errors of ~1% in stratospheric column ozone. The difference between OMI and GEMS retrieval characteristics is apparent for retrieving ozone layers above ~20 km, with a reduction in the sensitivity and an increase in the retrieval errors for GEMS. We further investigate whether GEMS can resolve the stratospheric ozone variation observed from high vertical resolution Earth Observing System (EOS) Microwave Limb Sounder (MLS). The differences in stratospheric ozone profiles between GEMS and MLS are comparable to those between OMI and MLS below ~3 hPa (~40 km), except with slightly larger biases and larger standard deviations by up to 5%. At pressure altitudes above ~3 hPa, GEMS retrievals show strong influence of a priori and large differences with MLS, which, however, can be sufficiently improved by using better a priori information. The GEMS-MLS differences show negative biases of less than 4% for stratospheric column ozone, with standard deviations of 1–3%, while OMI retrievals show similar agreements with MLS except for 1% smaller biases at middle and high latitudes. Based on the comparisons, we conclude that GEMS will measure tropospheric ozone and stratospheric ozone columns with accuracy comparable to that of OMI and ozone profiles with slightly worse performance than that of OMI below ~3 hPa.

scholarly journals Evaluation of ozone profile and tropospheric ozone retrievals from GEMS and OMI spectra

2012 ◽  
Vol 5 (5) ◽  
pp. 6733-6762 ◽  
Author(s):  
J. Bak ◽  
J. H. Kim ◽  
X. Liu ◽  
K. Chance ◽  
J. Kim
Keyword(s):  
Spectral Resolution ◽  
Tropospheric Ozone ◽  
Degrees Of Freedom ◽  
Stratospheric Ozone ◽  
A Priori ◽  
Ozone Monitoring Instrument ◽  
Ozone Profile ◽  
Retrieval Errors ◽  
Standard Deviations ◽  
Column Ozone

Abstract. Korea is planning to launch the GEMS (Geostationary Environment Monitoring Spectrometer) instrument into a Geostationary (GEO) platform in 2018 to monitor tropospheric air pollutants on an hourly basis over East Asia. GEMS will measure backscattered UV radiances covering the 300–500 nm wavelength range with a spectral resolution of 0.6 nm. The main objective of this study is to evaluate ozone profiles and stratospheric column ozone amounts retrieved from simulated GEMS measurements. Ozone Monitoring Instrument (OMI) Level 1B radiances, which have the spectral range 270–500 nm at spectral resolution of 0.42–0.63 nm, are used to simulate the GEMS radiances. An optimal estimation-based ozone profile algorithm is used to retrieve ozone profiles from simulated GEMS radiances. Firstly, we compare the retrieval characteristics (including averaging kernels, degrees of freedom for signal, and retrieval error) derived from the 270–330 nm (OMI) and 300–330 nm (GEMS) wavelength ranges. This comparison shows that the effect of not using measurements below 300 nm on tropospheric ozone retrievals is insignificant. However, the stratospheric ozone information decreases greatly from OMI to GEMS, by a factor of ∼2. The number of the independent pieces of information available from GEMS measurements is estimated to 3 on average in the stratosphere, with associated retrieval errors of ∼1% in stratospheric column ozone. The difference between OMI and GEMS retrieval characteristics is apparent for retrieving ozone layers above ∼20 km, with a reduction in the sensitivity and an increase in the retrieval errors for GEMS. We further investigate whether GEMS can resolve the stratospheric ozone variation observed from high vertical resolution EOS Microwave Limb Sounder (MLS). The differences in stratospheric ozone profiles between GEMS and MLS are comparable to those between OMI and MLS above ∼3 hPa (∼40 km) except with slightly larger biases and larger standard deviations by up to 5%. At pressure altitudes above ∼3 hPa, GEMS retrievals show strong influence of a priori and large differences with MLS, which, however, can be sufficiently improved by using better a priori information. The GEMS-MLS differences show negative biases of less than 4% for stratospheric column ozone, with standard deviations of 1–3%, while OMI retrievals show similar agreements with MLS except for 1% smaller biases at mid and high latitudes. Based on the comparisons, we conclude that GEMS will measure tropospheric ozone and stratospheric ozone columns with accuracy comparable to that of OMI and ozone profiles with slightly worse performance than that of OMI below ∼3 hPa.

Ozone Profile Retrieval from an Advanced Infrared Sounder: Experiments with Tropopause-Based Climatology and Optimal Estimation Approach

2010 ◽  
Vol 27 (7) ◽  
pp. 1123-1139 ◽  
Author(s):  
Jennifer C. Wei ◽  
Laura L. Pan ◽  
Eric Maddy ◽  
Jasna V. Pittman ◽  
Murty Divarkarla ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
A Priori ◽  
Optimal Estimation ◽  
Atmospheric Ozone ◽  
Atmospheric Infrared Sounder ◽  
Upper Troposphere ◽  
Ozone Profile ◽  
Retrieval Algorithms ◽  
The Impact ◽  
Instrument Sensitivity

Abstract Motivated by a significant potential for retrieving atmospheric ozone profile information from advanced satellite infrared sounders, this study investigates various methods to optimize ozone retrievals. A set of retrieval experiments has been performed to assess the impact of different background states (or the a priori states) and retrieval algorithms on the retrieved ozone profiles in the upper troposphere and lower stratosphere (UTLS) using Atmospheric Infrared Sounder (AIRS) measurements. A new tropopause-based ozone climatology, using publicly available global ozonesonde data to construct the a priori state, is described. Comparisons are made with the AIRS version 5 (v5) ozone climatology. The authors also present the result of a newly implemented optimal estimation (OE) algorithm and compare it to the current AIRS science team (AST) algorithm used in version 5. The ozone climatology using tropopause-referenced coordinates better preserves the shape and the magnitude of the ozone gradient across the tropopause, especially in the extratropical region. The results of the retrieval experiments indicate that the tropopause-referenced climatology not only helps to optimize the use of instrument sensitivity in the UTLS region, but it also provides better constraints to the OE algorithm.

scholarly journals A novel tropopause-related climatology of ozone profiles

2014 ◽  
Vol 14 (1) ◽  
pp. 283-299 ◽  
Author(s):  
V. F. Sofieva ◽  
J. Tamminen ◽  
E. Kyrölä ◽  
T. Mielonen ◽  
P. Veefkind ◽  
...  
Keyword(s):  
Climate Model ◽  
A Priori ◽  
Stratospheric Aerosol ◽  
Ozone Monitoring Instrument ◽  
Earth Observing System ◽  
Ozone Profile ◽  
High Vertical Resolution ◽  
Climate Model Simulations ◽  
Longitudinal Variability

Abstract. A new ozone climatology, based on ozonesonde and satellite measurements, spanning the altitude region between the earth's surface and ~60 km is presented (TpO3 climatology). This climatology is novel in that the ozone profiles are categorized according to calendar month, latitude and local tropopause heights. Compared to the standard latitude–month categorization, this presentation improves the representativeness of the ozone climatology in the upper troposphere and the lower stratosphere (UTLS). The probability distribution of tropopause heights in each latitude–month bin provides additional climatological information and allows transforming/comparing the TpO3 climatology to a standard climatology of zonal mean ozone profiles. The TpO3 climatology is based on high-vertical-resolution measurements of ozone from the satellite-based Stratospheric Aerosol and Gas Experiment II (in 1984 to 2005) and from balloon-borne ozonesondes from 1980 to 2006. The main benefits of the TpO3 climatology are reduced standard deviations on climatological ozone profiles in the UTLS, partial characterization of longitudinal variability, and characterization of ozone profiles in the presence of double tropopauses. The first successful application of the TpO3 climatology as a priori in ozone profile retrievals from Ozone Monitoring Instrument on board the Earth Observing System (EOS) Aura satellite shows an improvement of ozone precision in UTLS of up to 10% compared with the use of conventional climatologies. In addition to being advantageous for use as a priori in satellite retrieval algorithms, the TpO3 climatology might be also useful for validating the representation of ozone in climate model simulations.

scholarly journals Comparison of ozone profiles and influences from the tertiary ozone maximum in the night-to-day ratio above Switzerland

2017 ◽  
Vol 17 (17) ◽  
pp. 10259-10268 ◽  
Author(s):  
Lorena Moreira ◽  
Klemens Hocke ◽  
Niklaus Kämpfer
Keyword(s):  
Annual Variation ◽  
Lower Stratosphere ◽  
Microwave Radiometer ◽  
Relative Difference ◽  
Atmospheric Composition ◽  
Composition Change ◽  
Ozone Maximum ◽  
Ozone Profile ◽  
Mesospheric Ozone ◽  
The Mean

Abstract. Stratospheric and middle-mesospheric ozone profiles above Bern, Switzerland (46.95° N, 7.44° E; 577 m) have been continually measured by the GROMOS (GROund-based Millimeter-wave Ozone Spectrometer) microwave radiometer since 1994. GROMOS is part of the Network for the Detection of Atmospheric Composition Change (NDACC). A new version of the ozone profile retrievals has been developed with the aim of improving the altitude range of retrieval profiles. GROMOS profiles from this new retrieval version have been compared to coincident ozone profiles obtained by the satellite limb sounder Aura Microwave Limb Sounder (MLS). The study covers the stratosphere and middle mesosphere from 50 to 0.05 hPa (from 21 to 70 km) and extends over the period from July 2009 to November 2016, which results in more than 2800 coincident profiles available for the comparison. On average, GROMOS and MLS comparisons show agreement generally over 20 % in the lower stratosphere and within 2 % in the middle and upper stratosphere for both daytime and nighttime, whereas in the mesosphere the mean relative difference is below 40 % during the daytime and below 15 % during the nighttime. In addition, we have observed the annual variation in nighttime ozone in the middle mesosphere, at 0.05 hPa (70 km), characterized by the enhancement of ozone during wintertime for both ground-based and space-based measurements. This behaviour is related to the middle-mesospheric maximum in ozone (MMM).

scholarly journals Study of Clear Air Turbulence Related to Tropopause Folding over the Romanian Airspace

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1099
Author(s):  
Sabina Ștefan ◽  
Bogdan Antonescu ◽  
Ana Denisa Urlea ◽  
Livius Buzdugan ◽  
Meda Daniela Andrei ◽  
...  
Keyword(s):  
Large Scale ◽  
Lower Stratosphere ◽  
Meteorological Data ◽  
Horizontal Temperature Gradient ◽  
Jet Streams ◽  
Mountain Waves ◽  
Upper Troposphere ◽  
Air Turbulence ◽  
Upper Level ◽  
Tropopause Folding

Clear air turbulence (CAT) poses a significant threat to aviation. CAT usually occurs in the lower stratosphere and the upper troposphere. It is generally associated with large scale waves, mountain waves, jet streams, upper-level fronts and tropopause folds. Aircraft can experience CAT when flying in proximity of a tropopause fold. To better understand and diagnose tropopause fold- associated CAT we selected a series of cases from among those reported by pilots between June 2017 and December 2018 in the Romanian airspace. Data on turbulence were used in conjunction with meteorological data, satellite imagery, and vertical profiles. Additionally, a set of indices as Ellrod, horizontal temperature gradient, Dutton, and Brown were computed to diagnose CAT associated with tropopause folding. These indices were also analyzed to test the physics mechanisms that may explain the occurrence of severe turbulence. Results show that out of the 420 cases announced by pilots, severe turbulence was reported in 80 cases of which 13 were associated with tropopause folding.

scholarly journals Characterization of the long-term radiosonde temperature biases in the upper troposphere and lower stratosphere using COSMIC and Metop-A/GRAS data from 2006 to 2014

2017 ◽  
Vol 17 (7) ◽  
pp. 4493-4511 ◽  
Author(s):  
Shu-peng Ho ◽  
Liang Peng ◽  
Holger Vömel
Keyword(s):  
Lower Stratosphere ◽  
Temperature Measurements ◽  
Climate Data ◽  
Upper Troposphere ◽  
Global Trend ◽  
The Mean ◽  
Temperature Climate

Abstract. Radiosonde observations (RAOBs) have provided the only long-term global in situ temperature measurements in the troposphere and lower stratosphere since 1958. In this study, we use consistently reprocessed Global Positioning System (GPS) radio occultation (RO) temperature data derived from the COSMIC and Metop-A/GRAS missions from 2006 to 2014 to characterize the inter-seasonal and interannual variability of temperature biases in the upper troposphere and lower stratosphere for different radiosonde sensor types. The results show that the temperature biases for different sensor types are mainly due to (i) uncorrected solar-zenith-angle-dependent errors and (ii) change of radiation correction. The mean radiosonde–RO global daytime temperature difference in the layer from 200 to 20 hPa for Vaisala RS92 is equal to 0.20 K. The corresponding difference is equal to −0.06 K for Sippican, 0.71 K for VIZ-B2, 0.66 K for Russian AVK-MRZ, and 0.18 K for Shanghai. The global daytime trend of differences for Vaisala RS92 and RO temperature at 50 hPa is equal to 0.07 K/5 yr. Although there still exist uncertainties for Vaisala RS92 temperature measurement over different geographical locations, the global trend of temperature differences between Vaisala RS92 and RO from June 2006 to April 2014 is within ±0.09 K/5 yr. Compared with Vaisala RS80, Vaisala RS90, and sondes from other manufacturers, the Vaisala RS92 seems to provide the most accurate RAOB temperature measurements, and these can potentially be used to construct long-term temperature climate data records (CDRs). Results from this study also demonstrate the feasibility of using RO data to correct RAOB temperature biases for different sensor types.

scholarly journals Validation of Ozone Monitoring Instrument (OMI) ozone profiles and stratospheric ozone columns with Microwave Limb Sounder (MLS) measurements

2010 ◽  
Vol 10 (5) ◽  
pp. 2539-2549 ◽  
Author(s):  
X. Liu ◽  
P. K. Bhartia ◽  
K. Chance ◽  
L. Froidevaux ◽  
R. J. D. Spurr ◽  
...  
Keyword(s):  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Stratospheric Ozone ◽  
Random Noise ◽  
Ozone Monitoring Instrument ◽  
Middle Latitudes ◽  
Upper Limits ◽  
The Mean ◽  
Standard Deviations ◽  
Ozone Column

Abstract. We validate OMI ozone profiles between 0.22–215 hPa and stratospheric ozone columns down to 215 hPa (SOC215) against v2.2 MLS data from 2006. The validation demonstrates convincingly that SOC can be derived accurately from OMI data alone, with errors comparable to or smaller than those from current MLS retrievals, and it demonstrates implicitly that tropospheric ozone column can be retrieved accurately from OMI or similar nadir-viewing ultraviolet measurements alone. The global mean biases are within 2.5% above 100 hPa and 5–10% below 100 hPa; the standard deviations of the differences (1σ) are 3.5–5% between 1–50 hPa, 6–9% above 1 hPa and 8–15% below 50 hPa. OMI shows some latitude and solar zenith angle dependent biases, but the mean biases are mostly within 5% and the standard deviations are mostly within 2–5% except for low altitudes and high latitudes. The excellent agreement with MLS data shows that OMI retrievals can be used to augment the validation of MLS and other stratospheric ozone measurements made with even higher vertical resolution than that for OMI. OMI SOC215 shows a small bias of −0.6% with a standard deviation of 2.8%. When compared as a function of latitude and solar zenith angle, the mean biases are within 2% and the standard deviations range from 2.1 to 3.4%. Assuming 2% precision for MLS SOC215, we deduce that the upper limits of random-noise and smoothing errors for OMI SOC215 range from 0.6% in the southern tropics to 2.8% at northern middle latitudes.

scholarly journals Validation of Ozone Monitoring Instrument (OMI) ozone profiles and stratospheric ozone columns with Microwave Limb Sounder (MLS) measurements

2009 ◽  
Vol 9 (6) ◽  
pp. 24913-24943 ◽  
Author(s):  
X. Liu ◽  
P. K. Bhartia ◽  
K. Chance ◽  
L. Froidevaux ◽  
R. J. D. Spurr ◽  
...  
Keyword(s):  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Stratospheric Ozone ◽  
Random Noise ◽  
Ozone Monitoring Instrument ◽  
Middle Latitudes ◽  
Upper Limits ◽  
The Mean ◽  
Standard Deviations ◽  
Ozone Column

Abstract. We validate OMI ozone profiles between 0.22–215 hPa and stratospheric ozone columns down to 215 hPa (SOC215) against v2.2 MLS data from 2006. The validation demonstrates convincingly that SOC can be derived accurately from OMI data alone, with errors comparable to or smaller than those from current MLS retrievals, and it demonstrates implicitly that tropospheric ozone column can be retrieved accurately from OMI or similar nadir-viewing ultraviolet measurements alone. The global mean biases are within 2.5% above 100 hPa and 5–10% below 100 hPa; the standard deviations (1σ) are 3.5–5% between 1–50 hPa, 6–9% above 1 hPa and 8–15% below; 50 hPa. OMI shows some latitude and solar zenith angle dependent biases, but the mean biases are mostly within 5% and the standard deviations are mostly within 2–5% except for low altitudes and high latitudes. The excellent agreement with MLS data shows that OMI retrievals can be used to augment the validation of MLS and other stratospheric ozone measurements made with even higher vertical resolution than that for OMI. OMI SOC215 shows a small bias of −0.6% with a standard deviation of 2.8%. When compared as a function of latitude and solar zenith angle, the mean biases are within 2% and the standard deviations range from 2.1 to 3.4%. Assuming 2% precision for MLS SOC215, we deduce that the upper limits of random-noise and smoothing errors for OMI SOC215 range from 0.6% in the southern tropics to 2.8% at northern middle latitudes.

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