Impact of Using a New High-Resolution Solar Reference Spectrum on OMI Ozone Profile Retrievals

We evaluated a new high-resolution solar reference spectrum for characterizing space-borne Ozone Monitoring Instrument (OMI) measurements as well as for retrieving ozone profile retrievals over the ultraviolet (UV) wavelength range from 270 to 330 nm. The SAO2010 solar reference has been a standard for use in atmospheric trace gas retrievals, which is a composite of ground-based and balloon-based solar measurements from the Kitt Peak National Observatory (KPNO) and Air Force Geophysics Laboratory (AFGL), respectively. The new reference spectrum, called the TSIS-1 Hybrid Solar Reference Spectrum (HSRS), spans 202–2730 nm at a 0.01 to ~0.001 nm spectral resolution. The TSIS-1 HSRS in the UV region of interest in this study is a composite of AFGL and ground-based solar measurements from the Quality Assurance of Spectral Ultraviolet Measurements In Europe (QASUME) campaign, with a radiometric calibration that used the lower resolution Spectral Irradiance Monitor (SIM) instrument on the space-based Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) mission. The TSIS-1 HSRS radiometric uncertainties were below 1% whereas those of SAO2010 ranged from 5% in the longer UV part to 15% in the shorter UV part. In deriving slit functions and wavelength shifts from OMI solar irradiances, the resulting fitting residuals showed significant improvements of 0.5–0.7% (relatively, 20–50%) due to switching from the SAO2010 to the TSIS-1 HSRS. Correspondingly, in performing ozone profile retrievals from OMI radiances, the fitting residuals showed relative improvements of up to ~5% in 312–330 nm with relative differences of 5–7% in the tropospheric layer column ozone; the impact on stratospheric ozone retrievals was negligible.

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Validation of 10-year SAO OMI ozone profile (PROFOZ) product using Aura MLS measurements

Atmospheric Measurement Techniques ◽

10.5194/amt-11-17-2018 ◽

2018 ◽

Vol 11 (1) ◽

pp. 17-32 ◽

Cited By ~ 10

Author(s):

Guanyu Huang ◽

Xiong Liu ◽

Kelly Chance ◽

Kai Yang ◽

Zhaonan Cai

Keyword(s):

Stratospheric Ozone ◽

Radiometric Calibration ◽

High Altitudes ◽

Ozone Monitoring Instrument ◽

Data Set ◽

Spatial Consistency ◽

Ozone Profile ◽

Microwave Limb Sound ◽

Before And After ◽

Global Mean

Abstract. We validate the Ozone Monitoring Instrument (OMI) ozone profile (PROFOZ v0.9.3) product including ozone profiles between 0.22 and 261 hPa and stratospheric ozone columns (SOCs) down to 100, 215, and 261 hPa from October 2004 through December 2014 retrieved by the Smithsonian Astrophysical Observatory (SAO) algorithm against the latest Microwave Limb Sound (MLS) v4.2x data. We also evaluate the effects of OMI row anomaly (RA) on the retrieval by dividing the data set into before and after the occurrence of serious RA, i.e., pre-RA (2004–2008) and post-RA (2009–2014). During the pre-RA period, OMI ozone profiles agree very well with MLS data. After applying OMI averaging kernels to MLS data, the global mean biases (MBs) are within 3 % between 0.22 and 100 hPa, negative biases are within 3–9 % for lower layers, and the standard deviations (SDs) are 3.5–5 % from 1 to 40 hPa, 6–10 % for upper layers, and 5–20 % for lower layers. OMI shows biases dependent on latitude and solar zenith angle (SZA), but MBs and SDs are mostly within 10 % except for low and high altitudes of high latitudes and SZAs. Compared to the retrievals during the pre-RA period, OMI retrievals during the post-RA period degrade slightly between 5 and 261 hPa with MBs and SDs typically larger by 2–5 %, and degrade much more for pressure less than ∼ 5 hPa, with larger MBs by up to 8 % and SDs by up to 15 %, where the MBs are larger by 10–15 % south of 40∘ N due to the blockage effect of RA and smaller by 15–20 % north of 40∘ N due to the solar contamination effect of RA. The much worse comparisons at high altitudes indicate the UV1 channel of pixels that are not flagged as RA is still affected by the RA. During the pre-RA period, OMI SOCs show very good agreement with MLS data with global mean MBs within 0.6 % and SDs of 1.9 % for SOCs down to 215 and 261 hPa and of 2.30 % for SOC down to 100 hPa. Despite clearly worse ozone profile comparisons during the post-RA period, OMI SOCs only slightly degrade, with SDs larger by 0.4–0.6 % mostly due to looser spatial coincidence criteria as a result of missing data from RA and MBs larger by 0.4–0.7 %. Our retrieval comparisons indicate significant bias trends, especially during the post-RA period. The spatiotemporal variation of our retrieval performance suggests the need to improve OMI's radiometric calibration to maintain the long-term stability and spatial consistency of the PROFOZ product.

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Validation of 10-year SAO OMI Ozone Profile (PROFOZ) Product Using Aura MLS Measurements

10.5194/amt-2017-92 ◽

2017 ◽

Cited By ~ 4

Author(s):

Guanyu Huang ◽

Xiong Liu ◽

Kelly Chance ◽

Kai Yang ◽

Zhaonan Cai

Keyword(s):

Stratospheric Ozone ◽

Radiometric Calibration ◽

High Altitudes ◽

Ozone Monitoring Instrument ◽

Data Set ◽

Spatial Consistency ◽

Ozone Profile ◽

Microwave Limb Sound ◽

Before And After ◽

Global Mean

Abstract. We validate the Ozone Monitoring Instrument (OMI) ozone profile (PROFOZ) product including ozone profiles between 0.22–261 hPa and Stratospheric Ozone Columns (SOCs) down to 100, 215, and 261 hPa from October 2004 through December 2014 retrieved by the Smithsonian Astrophysical Observatory (SAO) algorithm against the latest Microwave Limb Sound (MLS) v4.2x data. We also evaluate the effects of OMI row anomaly (RA) on the retrieval by dividing the data set into before and after the occurrence of serious RA, i.e., pre-RA (2004–2008) and post-RA (2009–2014). During the pre-RA period, OMI ozone profiles agree very well with MLS data. Tthe global mean biases (MBs) are within 3 % between 0.22–100 hPa and negative 3–9 % for lower layers, and the standard deviations (SDs) are 3.5–5 % from 1–40 hPa, 6–10 % for upper layers and 5–20% for lower layers, after applying OMI averaging kernels to MLS data. OMI shows latitude and solar zenith angle (SZA) dependent biases, but MBs and SDs are mostly within 10 % except for low/high altitudes of high latitudes/SZAs. During the post-RA period, OMI retrievals degrade slightly between 5–261 hPa with MBs and SDs typically larger by 2–5%, and degrade much more, with larger MBs by up to 8 % and SDs by up to 15% for pressure less than ~ 5 hPa, where the MBs are larger by 10–15 % south of 40 °N due to the blockage effect of RA and smaller by 15–20 % north of 40 °N due to the solar contamination effect of RA. The much worse comparison at high altitudes indicates the UV-1 channel of pixels that are not flagged as RA is still affected by the RA. During the pre-RA period, OMI SOCs show very good agreement with MLS data with global mean MBs within 0.6 % and SDs of 1.9 % for SOCs down to 215 and 261 hPa and of 2.30 % for SOC down to 100 hPa. Despite clearly worse ozone profile comparison during the post-RA period, OMI SOCs only slightly degrade, with SDs larger by 0.4–0.6 % mostly due to looser spatial coincidence criterion as a result of missing data from RA and MBs larger by 0.4–0.7 %. The retrieval comparison indicates significant bias trends, especially during the post-RA period. The spatiotemporal variation of the retrieval performance suggests the need to improve OMI’s radiometric calibration to maintain the long-term stability and spatial consistency of the PROFOZ product. The good comparison with SOC down to 261 hPa supports that MLS ozone at 261 hPa, recommended for further evaluation by the MLS team, is suitable for scientific use.

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Stratosphere-troposphere ozone exchange from high resolution MLS ozone analyses

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-6129-2012 ◽

2012 ◽

Vol 12 (14) ◽

pp. 6129-6144 ◽

Cited By ~ 17

Author(s):

J. Barré ◽

V.-H. Peuch ◽

J.-L. Attié ◽

L. El Amraoui ◽

W. A. Lahoz ◽

...

Keyword(s):

High Resolution ◽

Transport Model ◽

Stratospheric Ozone ◽

Horizontal Resolution ◽

Ozone Profile ◽

High Horizontal Resolution ◽

The Impact ◽

Stratospheric Intrusions ◽

Troposphere Ozone ◽

Horizontal Grid

Abstract. We assimilate stratospheric ozone profiles from MLS (Microwave Limb Sounder) into the MOCAGE Chemistry Transport Model (CTM) to study Stratosphere-Troposphere Exchange (STE). This study uses two horizontal grid resolutions of 2° and 0.2°. The combined impacts of MLS ozone assimilation and high horizontal resolution are illustrated in two case studies where STE events occurred (23 June 2009 and 17 July 2009). At high resolution the filamentary structures of stratospheric air which characterise STE events are captured by the model. To test the impact of the assimilation and the resolution, we compare model outputs from different experiments (high resolution and low resolution; MLS assimilation run and free run) with independent data (MOZAIC aircraft ozone data; WOUDC ozone sonde network data). MLS ozone analyses show a better description of the Upper Troposphere Lower Stratosphere (UTLS) region and the stratospheric intrusions than the free model run. In particular, at high horizontal resolution the MLS ozone analyses present realistic filamentary ozone structures in the UTLS and laminae structures in the ozone profile. Despite a low aspect ratio between horizontal resolution and vertical resolution in the UTLS at high horizontal resolution, MLS ozone analyses improve the vertical structures of the ozone fields. Results from backward trajectories and ozone forecasts show that assimilation at high horizontal resolution of MLS ozone profiles between 10 hPa and 215 hPa has an impact on tropospheric ozone.

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Stratosphere-troposphere ozone exchange from high resolution MLS ozone analyses

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-33419-2011 ◽

2011 ◽

Vol 11 (12) ◽

pp. 33419-33463

Author(s):

J. Barré ◽

V.-H. Peuch ◽

J.-L. Attié ◽

L. El Amraoui ◽

W. A. Lahoz ◽

...

Keyword(s):

High Resolution ◽

Tropospheric Ozone ◽

Stratospheric Ozone ◽

Horizontal Resolution ◽

Ozone Profile ◽

High Horizontal Resolution ◽

The Impact ◽

Stratospheric Intrusions ◽

Troposphere Ozone ◽

Horizontal Grid

Abstract. We assimilate stratospheric ozone profiles from MLS (Microwave Limb Sounder) into the MOCAGE CTM model in order to study Stratosphere-Troposphere Exchange (STE). This study uses two horizontal grid resolution of 2° and 0.2°. The combined impacts of MLS ozone assimilation and high horizontal resolution are illustrated in two case studies where STE events occurred (23 June 2009 and 17 July 2009). At high resolution the fine filamentary structures of stratospheric air which characterise STE events are captured by the model. To test the impact of the assimilation and the resolution, we compare model outputs from different experiments (high resolution and low resolution; MLS assimilation run and free run) with independent data (MOZAIC aircraft ozone data; WOUDC ozone sonde network data) not used in the assimilation. MLS ozone analyses show a better description of the UTLS region and the stratospheric intrusions than the free model run. In particular, at high horizontal resolution the high resolution MLS ozone analyses presents fine filamentary ozone structures at the UTLS and laminae structures in the tropospheric ozone profile. By using MLS ozone analyses and high resolution, ozone fluxes through the tropopause show a range of results that lie within the range of similar previous studies. Results from backward trajectories and forecasts results show that assimilation at high horizontal resolution of MLS ozone profiles between 10 hPa and 215 hPa has an impact on tropospheric ozone.

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SOLAR-ISS: A new reference spectrum based on SOLAR/SOLSPEC observations

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731316 ◽

2018 ◽

Vol 611 ◽

pp. A1 ◽

Cited By ~ 23

Author(s):

M. Meftah ◽

L. Damé ◽

D. Bolsée ◽

A. Hauchecorne ◽

N. Pereira ◽

...

Keyword(s):

High Resolution ◽

Wavelength Range ◽

Solar Physics ◽

Space Station ◽

Solar Spectrum ◽

Total Solar Irradiance ◽

Spectral Irradiance ◽

Reference Spectrum ◽

The Difference ◽

The Impact

Context. Since April 5, 2008 and up to February 15, 2017, the SOLar SPECtrometer (SOLSPEC) instrument of the SOLAR payload on board the International Space Station (ISS) has performed accurate measurements of solar spectral irradiance (SSI) from the middle ultraviolet to the infrared (165 to 3088 nm). These measurements are of primary importance for a better understanding of solar physics and the impact of solar variability on climate. In particular, a new reference solar spectrum (SOLAR-ISS) is established in April 2008 during the solar minima of cycles 23–24 thanks to revised engineering corrections, improved calibrations, and advanced procedures to account for thermal and aging corrections of the SOLAR/SOLSPEC instrument. Aims. The main objective of this article is to present a new high-resolution solar spectrum with a mean absolute uncertainty of 1.26% at 1σ from 165 to 3000 nm. This solar spectrum is based on solar observations of the SOLAR/SOLSPEC space-based instrument.Methods. The SOLAR/SOLSPEC instrument consists of three separate double monochromators that use concave holographic gratings to cover the middle ultraviolet (UV), visible (VIS), and infrared (IR) domains. Our best ultraviolet, visible, and infrared spectra are merged into a single absolute solar spectrum covering the 165–3000 nm domain. The resulting solar spectrum has a spectral resolution varying between 0.6 and 9.5 nm in the 165–3000 nm wavelength range. We build a new solar reference spectrum (SOLAR-ISS) by constraining existing high-resolution spectra to SOLAR/SOLSPEC observed spectrum. For that purpose, we account for the difference of resolution between the two spectra using the SOLAR/SOLSPEC instrumental slit functions.Results. Using SOLAR/SOLSPEC data, a new solar spectrum covering the 165–3000 nm wavelength range is built and is representative of the 2008 solar minimum. It has a resolution better than 0.1 nm below 1000 nm and 1 nm in the 1000–3000 nm wavelength range. The new solar spectrum (SOLAR-ISS) highlights significant differences with previous solar reference spectra and with solar spectra based on models. The integral of the SOLAR-ISS solar spectrum yields a total solar irradiance of 1372.3 ± 16.9 Wm−2 at 1σ, that is yet 11 Wm−2 over the value recommended by the International Astronomical Union in 2015.

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

Atmospheric Measurement Techniques ◽

10.5194/amt-6-239-2013 ◽

2013 ◽

Vol 6 (2) ◽

pp. 239-249 ◽

Cited By ~ 27

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.

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Retrieving vertical ozone profiles from measurements of global spectral irradiance

Atmospheric Measurement Techniques ◽

10.5194/amt-10-4979-2017 ◽

2017 ◽

Vol 10 (12) ◽

pp. 4979-4994

Author(s):

Germar Bernhard ◽

Irina Petropavlovskikh ◽

Bernhard Mayer

Keyword(s):

High Resolution ◽

Total Ozone ◽

Greenland Ice Sheet ◽

Spectral Irradiance ◽

New Method ◽

Ozone Monitoring Instrument ◽

Monitoring Instrument ◽

Ozone Monitoring ◽

Vertical Ozone ◽

Vertical Ozone Profiles

Abstract. A new method is presented to determine vertical ozone profiles from measurements of spectral global (direct Sun plus upper hemisphere) irradiance in the ultraviolet. The method is similar to the widely used Umkehr technique, which inverts measurements of zenith sky radiance. The procedure was applied to measurements of a high-resolution spectroradiometer installed near the centre of the Greenland ice sheet. Retrieved profiles were validated with balloon-sonde observations and ozone profiles from the space-borne Microwave Limb Sounder (MLS). Depending on altitude, the bias between retrieval results presented in this paper and MLS observations ranges between −5 and +3 %. The magnitude of this bias is comparable, if not smaller, to values reported in the literature for the standard Dobson Umkehr method. Total ozone columns (TOCs) calculated from the retrieved profiles agree to within 0.7±2.0 % (±1σ) with TOCs measured by the Ozone Monitoring Instrument on board the Aura satellite. The new method is called the Global-Umkehr method.

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Evaluating the impact of spatial resolution on tropospheric NO<sub>2</sub> column comparisons within urban areas using high-resolution airborne data

Atmospheric Measurement Techniques ◽

10.5194/amt-12-6091-2019 ◽

2019 ◽

Vol 12 (11) ◽

pp. 6091-6111 ◽

Cited By ~ 11

Author(s):

Laura M. Judd ◽

Jassim A. Al-Saadi ◽

Scott J. Janz ◽

Matthew G. Kowalewski ◽

R. Bradley Pierce ◽

...

Keyword(s):

High Resolution ◽

Los Angeles ◽

Spatial Heterogeneity ◽

Spatial Resolution ◽

Urban Areas ◽

High Temporal Resolution ◽

Ozone Monitoring Instrument ◽

Vertical Column ◽

Monitoring Instrument ◽

The Impact

Abstract. NASA deployed the GeoTASO airborne UV–visible spectrometer in May–June 2017 to produce high-resolution (approximately 250 m×250 m) gapless NO2 datasets over the western shore of Lake Michigan and over the Los Angeles Basin. The results collected show that the airborne tropospheric vertical column retrievals compare well with ground-based Pandora spectrometer column NO2 observations (r2=0.91 and slope of 1.03). Apparent disagreements between the two measurements can be sensitive to the coincidence criteria and are often associated with large local variability, including rapid temporal changes and spatial heterogeneity that may be observed differently by the sunward-viewing Pandora observations. The gapless mapping strategy executed during the 2017 GeoTASO flights provides data suitable for averaging to coarser areal resolutions to simulate satellite retrievals. As simulated satellite pixel area increases to values typical of TEMPO (Tropospheric Emissions: Monitoring Pollution), TROPOMI (TROPOspheric Monitoring Instrument), and OMI (Ozone Monitoring Instrument), the agreement with Pandora measurements degraded, particularly for the most polluted columns as localized large pollution enhancements observed by Pandora and GeoTASO are spatially averaged with nearby less-polluted locations within the larger area representative of the satellite spatial resolutions (aircraft-to-Pandora slope: TEMPO scale =0.88; TROPOMI scale =0.77; OMI scale =0.57). In these two regions, Pandora and TEMPO or TROPOMI have the potential to compare well at least up to pollution scales of 30×1015 molecules cm−2. Two publicly available OMI tropospheric NO2 retrievals are found to be biased low with respect to these Pandora observations. However, the agreement improves when higher-resolution a priori inputs are used for the tropospheric air mass factor calculation (NASA V3 standard product slope =0.18 and Berkeley High Resolution product slope =0.30). Overall, this work explores best practices for satellite validation strategies with Pandora direct-sun observations by showing the sensitivity to product spatial resolution and demonstrating how the high-spatial-resolution NO2 data retrieved from airborne spectrometers, such as GeoTASO, can be used with high-temporal-resolution ground-based column observations to evaluate the influence of spatial heterogeneity on validation results.

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Characterization and Correction of OMPS Nadir Mapper Measurements for Ozone Profile Retrievals

10.5194/amt-2017-298 ◽

2017 ◽

Author(s):

Juseon Bak ◽

Xiong Liu ◽

Jae-Hwan Kim ◽

David P. Haffner ◽

Kelly Chance ◽

...

Keyword(s):

Tropospheric Ozone ◽

Degrees Of Freedom ◽

Optimal Estimation ◽

Inversion Method ◽

Radiometric Calibration ◽

Ozone Monitoring Instrument ◽

Ozone Profile ◽

Noise Error ◽

Significant Wavelength ◽

Cross Track

Abstract. This paper verifies and corrects the Ozone Mapping and Profiler Suite (OMPS) Nadir Mapper (NM) Level 1B v2.0 measurements with the aim of producing accurate ozone profile retrievals using an optimal estimation based inversion method to fit measurements in the spectral range 302.5–340 nm. The evaluation of available slit functions demonstrates that preflight-measured slit functions well represent OMPS measurements compared to derived Gaussian slit functions. Our initial OMPS fitting residuals contain significant wavelength and cross-track dependent biases, resulting into serious cross-track striping errors in the tropospheric ozone retrievals. To eliminate the systematic component of the fitting residuals, we apply “soft calibration” to OMPS radiances. With the soft calibration the amplitude of fitting residuals decreases from ~ 1 % to 0.2 % over low/mid latitudes, and thereby the consistency of tropospheric ozone retrievals between OMPS and the Ozone Monitoring Instrument (OMI) is substantially improved. A common mode correction is also implemented for additional radiometric calibration; it improves retrievals especially at high latitudes where the amplitude of fitting residuals decreases by a factor of ~ 2. We estimate the floor noise error of OMPS measurements from standard deviations of the fitting residuals. The derived error in the Huggins band (~ 0.1 %) is twice the OMPS L1B measurement error. OMPS floor noise errors better constrains our retrievals, leading to improving information content of ozone and reducing fitting residuals. The final precision of the fitting residuals is less than 0.1 % in the low/mid latitude, with ~ 1 degrees of freedom for signal for the tropospheric ozone, meeting the general requirements for successful tropospheric ozone retrievals.

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Retrieving Vertical Ozone Profiles from Measurements of Global Spectral Irradiance

10.5194/amt-2017-179 ◽

2017 ◽

Author(s):

Germar Bernhard ◽

Irina Petropavlovskikh ◽

Bernhard Mayer

Keyword(s):

High Resolution ◽

Total Ozone ◽

Greenland Ice Sheet ◽

Spectral Irradiance ◽

New Method ◽

Ozone Monitoring Instrument ◽

Monitoring Instrument ◽

Ozone Monitoring ◽

Vertical Ozone ◽

Vertical Ozone Profiles

Abstract. A new method is presented to determine vertical ozone profiles from measurements of spectral global (direct Sun plus upper hemisphere) irradiance in the UV. The method is similar to the widely used Umkehr technique, which inverts measurements of zenith sky radiance. The procedure was applied to measurements of a high-resolution spectroradiometer installed near the centre of the Greenland ice sheet. Retrieved profiles were validated with balloon sonde observations and ozone profiles from the space-borne Microwave Limb Sounder (MLS). Depending on altitude, the bias between retrieval results presented in this paper and MLS observations ranges between −5 % and +3 %. The magnitude of this bias is comparable, if not smaller, to values reported in the literature for the standard Dobson Umkehr method. Total ozone columns (TOCs) calculated from the retrieved profiles agree to within 0.7 ± 2.0 % (±1σ) with TOCs measured by the Ozone Monitoring Instrument (OMI) onboard the Aura satellite. The new method is called the “Global-Umkehr” method.

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