Round-robin evaluation of nadir ozone profile retrievals: methodology and application to MetOp-A GOME-2

Keppens, Arno; Lambert, Jean-Christopher; Granville, J.; Miles, Georgina; Siddans, Richard; Peet, Jacob C. A. van; Hubert, D.; Verhoelst, Tijl; Delcloo, Andy; Godin‐Beekmann, Sophie; Kivi, Rigel; Stübi, René; Zehner, Claus

doi:10.5194/amt-8-2093-2015

Cited by 31 publications

(75 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…son with reference measurements from ground-based instruments (see, e.g. Keppens et al, 2015, this issue, for a detailed protocol). In these validation exercises, a compromise must be made between, on the one hand, abundance of comparison pairs, and on the other hand, non-instrumental comparison errors due to non-perfect co-location in space and time between satellite and ground-based measurements.…”

mentioning

confidence: 99%

Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons

et al. 2015

Self Cite

View full text Add to dashboard Cite

Abstract. Comparisons with ground-based correlative measurements constitute a key component in the validation of satellite data on atmospheric composition. The error budget of these comparisons contains not only the measurement errors but also several terms related to differences in sampling and smoothing of the inhomogeneous and variable atmospheric field. A versatile system for Observing System Simulation Experiments (OSSEs), named OSSSMOSE, is used here to quantify these terms. Based on the application of pragmatic observation operators onto high-resolution atmospheric fields, it allows a simulation of each individual measurement, and consequently, also of the differences to be expected from spatial and temporal field variations between both measurements making up a comparison pair. As a topical case study, the system is used to evaluate the error budget of total ozone column (TOC) comparisons between GOME-type direct fitting (GODFITv3) satellite retrievals from GOME/ERS2, SCIAMACHY/Envisat, and GOME-2/MetOp-A, and ground-based direct-sun and zenith-sky reference measurements such as those from Dobsons, Brewers, and zenith-scattered light (ZSL-)DOAS instruments, respectively. In particular, the focus is placed on the GODFITv3 reprocessed GOME-2A data record vs. the ground-based instruments contributing to the Network for the Detection of Atmospheric Composition Change (NDACC). The simulations are found to reproduce the actual measurements almost to within the measurement uncertainties, confirming that the OSSE approach and its technical implementation are appropriate. This work reveals that many features of the comparison spread and median difference can be understood as due to metrological differences, even when using strict colocation criteria. In particular, sampling difference errors exceed measurement uncertainties regularly at most mid-and high-latitude stations, with values up to 10 % and more in extreme cases. Smoothing difference errors only play a role in the comparisons with ZSL-DOAS instruments at high latitudes, especially in the presence of a polar vortex due to the strong TOC gradient it induces. At tropical latitudes, where TOC variability is lower, both types of errors remain below about 1 % and consequently do not contribute significantly to the comparison error budget. The detailed analysis of the comparison results, including the metrological errors, suggests that the published random measurement uncertainties for GODFITv3 reprocessed satellite data are potentially overestimated, and adjustments are proposed here. This successful application of the OSSSMOSE system to close for the first time the error budget of TOC comparisons, bodes well for potential future applications, which are briefly touched upon.

show abstract

mentioning

confidence: 99%

Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…The comparative analysis follows later in Section 5. The uncertainties related to the sonde and lidar FRM used in this work are discussed in Keppens et al (2015) and Hubert et al (2016). Essentially, ozonesondes measure the vertical profile of ozone partial pressure with order of 10m vertical sampling (100-150m actual vertical resolution) from the ground up to the burst point of the balloon, usually between 30 and 33 km.…”

Section: L3 Monthly Gridded Data 10mentioning

confidence: 99%

“…The satellite Level-2 and ground-based profiles' vertical smoothing is in this work 10 by default harmonised (i.e. reducing the vertical smoothing difference error) by averaging kernel smoothing of the FRM (Keppens et al, 2015). The mass-conservation regridded ground-based profile is thereby converted into its vertically smoothed form ′ by multiplication with the satellite profile's averaging kernel matrix (in partial column units), yet taking into account the kernel's sensitivity to the prior profile of the optimal estimation retrieval:…”

Section: Co-location and Harmonisation Of Satellite And Reference Datamentioning

confidence: 99%

“…Calculating difference profiles also requires harmonisation of the satellite and reference ozone profiles in terms of at least their unit representation and vertical sampling (Keppens et al, 2015). While ozonesondes report measurements in partial pressure, easily converted into volume-mixing-ratio (VMR) units and also in number-density (ND) using the on-board PTU measurements, the lidar data are given in number density and in general the files do not provide associated temperature profiles for a beforehand ND to VMR conversion.…”

Section: Co-location and Harmonisation Of Satellite And Reference Datamentioning

confidence: 99%

“…A major goal of the Ozone_cci subproject is to produce time series of tropospheric and stratospheric ozone distributions from current and historical missions that meet the requirements for reducing the uncertainty in estimates of global radiative forcing. Yet Keppens et al (2015), based on analysis principles discussed by Rodgers (2000), have illustrated that the comparison of nadir (ozone) profiles with FRM, although very informative on a specific data product, usually is insufficient to fully appreciate the relative quality of 30 different retrieval products and to verify their compliance with user requirements. The present work therefore adopts the more exhaustive seven-step evaluation approach established in Keppens et al, 2015, including (1) satellite data collection Atmos.…”

Section: Introduction 10mentioning

confidence: 99%

See 2 more Smart Citations

Quality assessment of the Ozone_cci Climate Research Data Package (release 2017): 2. Ground-based validation of nadir ozone profile data products

Keppens¹,

Lambert²,

Granville³

et al. 2018

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Atmospheric ozone plays a key role in air quality and the radiation budget of the Earth, both directly and through its chemical influence on other trace gases. Assessments of the atmospheric ozone distribution and associated climate change therefore demand accurate vertically-resolved ozone observations with both stratospheric and tropospheric sensitivity, both on the global and regional scales, and both in the long term and at shorter timescales. Such observations have been acquired 25 by two series of European nadir-viewing ozone profilers, namely the scattered-light UV-visible spectrometers of the GOME family, launched regularly since 1995 (GOME, SCIAMACHY, OMI, GOME-2A/B, TROPOMI, and the upcoming Sentinel-

show abstract

Validation practices for satellite‐based Earth observation data across communities

Loew

Bell

Brocca

et al. 2017

Reviews of Geophysics

Self Cite

179

137

View full text Add to dashboard Cite

Assessing the inherent uncertainties in satellite data products is a challenging task. Different technical approaches have been developed in the Earth Observation (EO) communities to address the validation problem which results in a large variety of methods as well as terminology. This paper reviews state‐of‐the‐art methods of satellite validation and documents their similarities and differences. First, the overall validation objectives and terminologies are specified, followed by a generic mathematical formulation of the validation problem. Metrics currently used as well as more advanced EO validation approaches are introduced thereafter. An outlook on the applicability and requirements of current EO validation approaches and targets is given.

show abstract

Round-robin evaluation of nadir ozone profile retrievals: methodology and application to MetOp-A GOME-2

Cited by 31 publications

References 36 publications

Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons

Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons

Quality assessment of the Ozone_cci Climate Research Data Package (release 2017): 2. Ground-based validation of nadir ozone profile data products

Validation practices for satellite‐based Earth observation data across communities

Contact Info

Product

Resources

About