The FDR4ATMOS Project

Introduction

• The Fundamental Data Record for ATMOSpheric Composition (FDR4ATMOS) project is part of the ESA Long Term Data Preservation (LTDP) programme
• It has two main tasks
  • Task A: Correction of SCIAMACHY degradation
  • Task B: Creating a cross instrument time series of radiances (Level 1) of GOME-1 and SCIAMACHY
• The project successfully concluded phase 1 with prepatory work
• Phase 2 has just started with an end in October 2022

Goals Task A

Goals Task A

• After the re-processing of SCIAMACHY data with the latest version, O_3 total column data showed a drift
• The previous processor version did not show a drift
• Algorithms for the retrieval were not changed w.r.t. previous processor version
• ⇒ Changes in Level 1 algorithms led to the observed O_3 drift
• The major Level 1 change in the new version was the degradation correction
• Subtle spectral changes mis-interpreted as a O_3 signature could lead to a trend
• In Task A the degradation correction will be updated to correct the drift

Task A: O_3 Validation

Task A: Results

Task A: Quick Look

Task A: Results

• Different solutions were checked
• The best solution leads to an overall degradation correction similar to the previous Level 1 version.
• The solution is empirical, the actual cause of the total ozone trend is not yet clarified.
• The derived total ozone is very similar to Level 2 version 6.01 with deviations below 0.3 % and no trend added.
• Validation using ground based data with an extended data set is under way

Goals Task B

What is a FDR?

FDR

A FDR is a long-term record of selected EO Level 1 parameters, possibly multi-instrument, which provides improvements of performance with respect to the individual mission datasets.

Reminder GOME-1 and SCIAMACHY

Both instruments span 17 years of data. The table shows only the relevant channels for FDR4ATMOS

Goals Task B

• The main objective of the FDR4ATMOS project is to develop a cross-instrument Level 1 product for GOME-1 and SCIAMACHY for the UV, VIS and NIR spectral range
• The focus on the spectral windows used for O3, SO2, NO2 total column retrieval and the determination of cloud properties.
• Contrary to other projects, we do not aim to build harmonised time series based on Level 2 products (geophysical parameters)
• The FDR4ATMOS products will be based on Level 1, i.e. radiances and reflectances.
• The goal of the FDR4ATMOS project is to generate harmonised data sets that allows to use them directly in long-term trend analysis, independently of the instrument.}

Challenges and open points

• GOME-1 and SCIAMACHY do not have exact co-locations (different orbits)
• To avoid a bias due to instrument effects comparison scenes have to cover
  • different observation geometries
  • different signal intensities
  • different signal polarisations
• Spatial resolution of GOME-1 is coarse, but downscaling SCIAMACHY is not useful for Level 2
• Contrary to previous cross-calibrations (e.g. FIDUCEO project) harmonisation has to be done on a highly resolved spectral grid

Challenges and open points - spatial resolution

Coarser GOME resolution consequences

• less cloud free pixels
• hampers detection of sources
• makes ground based validation less representative

Tasks B Breakdown

Preparations and Input

Task Breakdown:

• Preparations:
  • Assessment of current Level 1 data
  • Establishment of requirements (from Level 2 point of view)
  • Updates of degradation corrections (for SCIAMACHY see task A)
  • Determination of the error sources and uncertainties
• Input data
  • Define matching scene criteria
  • Collect matching scenes
  • Review on-ground data (for uncertainty analysis)

GOME Degradation

• Reflectivity changes with time, i.e. differential degradation of radiance and irradiance light paths
• Degradation depends on
  • Viewing angle (east, nadir, west)
  • Spectral region (UV, VIS, NIR)
• More scenes will be investigated, e.g., ocean, ice, deep convective clouds

GOME reflectance at PICS Libya-4 (Sahara desert)

Algorithm Development and Testing

• Algorithm development
  • Investigate scene dependencies
  • Derive harmonisation model
  • Derivation of uncertainties
  • Implement processing chain
• Testing
  • Test against references (e.g. solar irradiances, CEOS ground scenes)
  • Test impact on target Level 2 species

Simplified Flow

Task B Phase 1

Task B Phase 1

In Phase activities

• Summary of calibration chains and first definition of a uncertainty tree
• Assessment of Level 1 data
• Analysis of Level 2 requirements for long term time series
• Establishment of research needs
• Draft of product format
• Draft of validation plan

Summary and Conclusions

• The FDR4ATMOS project aims to
  • Deliver high quality SCIAMACHY data by improving the degradation correction
  • Deliver FDRs on Level 1 Basis
• In phase 1 the SCIAMACHY degradation correction was updated
• The FDR requirements and research needs were established
• Phase 2 will start in May and aims to
  • Generate FDRs of UV, VIS, NIR spectral regions
  • Build an operational, quality controlled processing chain
  • Deliver FDR products that are in a standard format and easily accessible
• We want to develop methodologies and algorithms for the harmonisation of spectrally resolved data that can also be used for current and future instruments

FDR4ATMOS Team

DLR-IMF (prime)

G. Lichtenberg, S. Slijkhuis, M. Hamidouche, M. Coldewey-Egbers, B. Aberle

IUP Bremen

S. Noël, K. Bramstedt, T. Hilbig, T. Bösch

BIRA-IASB

J.-C. Lambert, J. van Gent, D. Hubert

NPL UK

P. Green, S. Hunt

ESS

M. Krijger

ESA

A. Dehn

SERCO

G. Brizzi