G5.06 Extraction, analysis, and visualization tools to exploit the potential of fiducial reference measurements are currently only rudimentary

Gap abstract: 

Climate research and services have an increasing need to consider a large amount of observational data and model outputs simultaneously in applications. Because the data volumes provided by satellite observations and ensemble model runs have increased to levels that prevent easy download to local compute environments, there is an enhanced need for tools that provide functionality for data extraction, analysis, and visualisation at source or on cloud compute resources. At the same time, fiducial reference measurements are needed to provide evidence for the quality of satellite observations and models, but the aforementioned tools to exploit the potential of such reference measurements are currently only rudimentary. This in particular includes tools to analyse and display uncertainty of comparison results due to differences caused by mismatches in space and time of data used in comparisons

Part I Gap description

Primary gap type: 
  • Technical (missing tools, formats etc.)
Secondary gap type: 
  • Knowledge of uncertainty budget and calibration
  • Uncertainty in relation to comparator measures
ECVs impacted: 
  • Temperature,Water vapour, Ozone, Aerosols, Carbon Dioxide, Methane
User category/Application area impacted: 
  • Operational services and service development (meteorological services, environmental services, Copernicus Climate Change Service (C3S) and Atmospheric Monitoring Service (CAMS), operational data assimilation development, etc.)
  • International (collaborative) frameworks and bodies (space agencies, EU institutions, WMO programmes/frameworks etc.)
  • Climate research (research groups working on development, validation and improvement of ECV Climate Data Records)
Non-satellite instrument techniques involved: 
  • Independent of instrument technique
  • The tools to be developed to address this gap in the context of validation work should be based on the traceability principles and Cal/Val best practices referred to in G5.07. Hence G5.07 should be addressed before G5.06 as it represents a contribution to the latter. 

Detailed description: 

Services that provide data extraction, analysis, and visualization tools exist for comparisons of gridded data, but are currently only rudimentary for comparisons of satellite and non-satellite fiducial reference measurements based on data co-locations, which are needed for the validation of satellite measurements and derived products. In particular, analysis capabilities that for instance allow analysis at different time or spatial scales are missing. While measurement uncertainties are at least displayed by some existing services, e.g., the FP7 NORS project, the visualisation of uncertainty arising from differences in spatiotemporal sampling is generally not included, but is needed to fully understand the uncertainty budget of a specific comparison.

The user survey undertaken by GAIA-CLIM indicated a clear need for such a capability to be developed. But challenges remain, because whatever analysis / visualisation tool can be provided, it will not necessarily match all individual needs. The GAIA-CLIM user survey also indicated that the analysis of the co-locations provided by the Virtual Observatory may not solely be used to evaluate satellite measurements but also vice-versa, the satellite measurements may be used to evaluate the quality of the reference measurements, e.g., their temporal consistency. Such a flexible tool does not exist to date. 

Operational space missions or space instruments impacted: 
  • Independent of specific space mission or space instruments
Validation aspects addressed: 
  • Radiance (Level 1 product)
  • Geophysical product (Level 2 product)
  • Gridded product (Level 3)
  • Assimilated product (Level 4)
  • Representativity (spatial, temporal)
Gap status after GAIA-CLIM: 
  • GAIA-CLIM explored and demonstrated potential solutions to close this gap in the future

GAIA-CLIM WP5 has developed a Virtual Observatory that addresses this gap partly for a limited set of ECVs and with several limitations concerning the representation of the mismatch errors. At the end of the GAIA-CLIM project, there will be a prototype tool that can be developed further in the future. 

Part II Benefits to resolution and risks to non-resolution

Identified benefitUser category/Application area benefittedProbability of benefit being realisedImpacts
The existence of the GAIA-CLIM Virtual Observatory allows quality assessment for satellite data and derived products with a high potential to be made operational. It can also be extended to more GCOS ECVs.
  • All users and application areas will benefit from it
  • High
The GAIA-CLIM Virtual Observatory can be used in different contexts such as validation tool for products contained in the C3S CDS,
as baseline for satellite-retrieval studies and comparisons, and as a satellite Cal/Val tool in space agencies that have the capability to deal with many different sensors.
These usages increase the visibility of the value of non-satellite reference measurements and make sustained funding more viable.
The data extraction capability of the VO allows the export of data from the Virtual Observatory in user-friendly formats.
  • All users and application areas will benefit from it
  • High
The provision of a data extraction and visualisation capability considering the uncertainty aspects of data comparison can make further developments of retrieval schemes for considered variables easier.
This usage increases the visibility of the value of non-satellite reference measurements and makes sustained funding more viable.
Identified riskUser category/Application area at riskProbability of risk being realisedImpacts
Lack of the described tools prevents optimal use of reference measurements leading to potential issues with the justification of the measurements in the future.
  • All users and application areas will suffer from it.
  • High
Derived global products from satellite may suffer in quality from inadequate evaluation of the measurements and retrieval schemes used to generate them. This can hamper applications supporting decision and policymaking.

Part III Gap remedies

Gap remedies: 

Remedy 1: Operationalisation of a satellite – non-satellite matchups facility with appropriate discovery and user tools

Primary gap remedy type: 
Secondary gap remedy type: 
Proposed remedy description: 

The Virtual Observatory contains a still rudimentary data extraction capability that allows the export of co-located data from it in user-friendly, self-descriptive NetCDF format. The format also allows comparison data being amended by meta-data of the comparison, e.g., the used co-location criteria, etc., but this has not been realised within the lifetime of the GAIA-CLIM project. Such a format also supports analysis of the data in ways that may not be enabled, at least initially, in the final demonstrator version of the Virtual Observatory. Data extraction tools also are capable of sub-setting each data source contained in the co-location data base by ECV, time and location, observing system, and other boundary conditions such as surface type.

To exploit the co-location data base proposed as remedy 2 for gap G5.01, analysis tools must be developed to provide statistics and various indicators for a comparison that meet user needs as indicated by the GAIA-CLIM user survey outcomes. These analysis tools must have some flexibility, such as interchanging the reference in a comparison and the ability to perform analysis at different time and eventually space scales.

Visualisation tools need to be capable of displaying multiple co-located parameters to circumvent the complexity of comparing datasets of varying type and geometries, e.g. time series and instantaneous, spatially localised and large spatial extent observations, column-integrated observations, and vertical profiles, etc. Special attention must be paid to the specification of graphical representation of individual parameters and various uncertainty measures, including the smoothing uncertainty.

Tool development should look to benefit from existing elements and capabilities whenever possible. All developed tools need to be accessible via a GUI that also needs to be developed. GAIA-CLIM has developed a demonstrator facility with a limited number of static examples. Further development and operationalisation of the facility would be required to enable reliable near-real-time and delayed mode exploitation for a broader range of satellite instruments and ECVs. 


The GAIA-CLIM Virtual Observatory could serve as the basis for the development of an operational tool for the Evaluation and Quality Control pillar of the C3S, if being made available after the end of the GAIA-CLIM project. Such an implementation represents an important step towards an easily accessible comparison tool that considers all kinds of uncertainty relevant for data comparisons. 

Measurable outcome of success: 

Developed tools for data extraction and display for co-located satellite and non-satellite measurements being accessible via an operational graphical user interface

Expected viability for the outcome of success: 
  • Medium
  • High
Scale of work: 
  • Programmatic multi-year, multi-institution activity
Time bound to remedy: 
  • Less than 5 years
Indicative cost estimate (investment): 
  • Medium cost (< 5 million)
Indicative cost estimate (exploitation): 
  • Yes
Potential actors: 
  • Copernicus funding
  • ESA, EUMETSAT or other space agency
  • SMEs/industry