Abstract

Abstract. This paper assesses the quality of IASI (Infrared Atmospheric Sounding Interferometer)/Metop-A (IASI-A) and IASI/Metop-B (IASI-B) ozone (O3) products (total and partial O3 columns) retrieved with the Fast Optimal Retrievals on Layers for IASI Ozone (FORLI-O3; v20151001) software for 9 years (2008–July 2017) through an extensive intercomparison and validation exercise using independent observations (satellite, ground-based and ozonesonde). Compared with the previous version of FORLI-O3 (v20140922), several improvements have been introduced in FORLI-O3 v20151001, including absorbance look-up tables recalculated to cover a larger spectral range, with additional numerical corrections. This leads to a change of ∼4 % in the total ozone column (TOC) product, which is mainly associated with a decrease in the retrieved O3 concentration in the middle stratosphere (above 30 hPa/25 km). IASI-A and IASI-B TOCs are consistent, with a global mean difference of less than 0.3 % for both daytime and nighttime measurements; IASI-A is slightly higher than IASI-B. A global difference of less than 2.4 % is found for the tropospheric (TROPO) O3 column product (IASI-A is lower than IASI-B), which is partly due to a temporary issue related to the IASI-A viewing angle in 2015. Our validation shows that IASI-A and IASI-B TOCs are consistent with GOME-2 (Global Ozone Monitoring Experiment-2), Dobson, Brewer, SAOZ (Système d'Analyse par Observation Zénithale) and FTIR (Fourier transform infrared) TOCs, with global mean differences in the range of 0.1 %–2 % depending on the instruments compared. The worst agreement with UV–vis retrieved TOC (satellite and ground) is found at the southern high latitudes. The IASI-A and ground-based TOC comparison for the period from 2008 to July 2017 shows the long-term stability of IASI-A, with insignificant or small negative drifts of 1 %–3 % decade−1. The comparison results of IASI-A and IASI-B against smoothed FTIR and ozonesonde partial O3 columns vary with altitude and latitude, with the maximum standard deviation being seen for the 300–150 hPa column (20 %–40 %) due to strong ozone variability and large total retrievals errors. Compared with ozonesonde data, the IASI-A and IASI-B O3 TROPO column (defined as the column between the surface and 300 hPa) is positively biased in the high latitudes (4 %–5 %) and negatively biased in the midlatitudes and tropics (11 %–13 % and 16 %–19 %, respectively). The IASI-A-to-ozonesonde TROPO comparison for the period from 2008 to 2016 shows a significant negative drift in the Northern Hemisphere of -8.6±3.4 % decade−1, which is also found in the IASI-A-to-FTIR TROPO comparison. When considering the period from 2011 to 2016, the drift value for the TROPO column decreases and becomes statistically insignificant. The observed negative drifts of the IASI-A TROPO O3 product (8 %–16 % decade−1) over the 2008–2017 period might be taken into consideration when deriving trends from this product and this time period.

Highlights

  • Ozone (O3) plays a major role in the chemical and thermal balance of the atmosphere

  • This leads to a change of ∼ 4 % in the total ozone column (TOC) product, which is mainly associated with a decrease in the retrieved O3 concentration in the middle stratosphere

  • The Infrared Atmospheric Sounding Interferometer (IASI) O3 products processed with FORLI v20151001 are part of the ESA Ozone_cci and European Centre for MediumRange Weather Forecasts (ECMWF) C3S projects, which focus on building consolidated climate-relevant ozone datasets as essential climate variables (ECVs)

Read more

Summary

Introduction

Ozone (O3) plays a major role in the chemical and thermal balance of the atmosphere. In the stratosphere, O3 protects the biosphere and humans from harmful ultraviolet (UV) radiation. It was shown that this improvement is mainly associated with a decrease in the retrieved O3 concentration in the middle stratosphere (MS, above 30 hPa/25 km) This O3 retrieval algorithm (FORLI-O3 v20151001) is currently being implemented in the EUMETSAT processing facility under the auspices of the “Ozone and Atmospheric Composition Monitoring Satellite Application Facility” (AC SAF) project in order to operationally distribute Level 2 IASI O3 profiles to users through the EUMETCast system in 2018. We assess the quality of the IASI O3 products retrieved using FORLI-O3 v20151001 (hereafter referred as to “IASI O3 products”), with GOME-2 (Global Ozone Monitoring Experiment-2; on Metop), ground-based network data (Brewer, Dobson, SAOZ – Système d’Analyse par Observation Zénithale – and FTIR – Fourier transform infrared) and ozonesonde measurements.

IASI ozone retrievals
Ground-based data
Ozonesonde data
Comparison methodology
Comparison with FTIR and ozonesonde data
Comparison with GOME-2 TOCs
Comparison with Brewer–Dobson TOCs
Comparison with SAOZ TOCs
Comparison with FTIR TOCs and partial ozone columns
Comparison with ozonesonde partial ozone columns
Findings
Summary
Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.