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A Metrological Approach to Producing Harmonised Fundamental Climate Data Records from Long-Term Sensor Series Data

Hunt, S E; Quast, R; Harris, P M; Mittaz, J P D; Woolliams, E R; Giering, R; Dilo, A; Merchant, C J (2018) A Metrological Approach to Producing Harmonised Fundamental Climate Data Records from Long-Term Sensor Series Data. In: IGARSS 2018 - IEEE International Geoscience and Remote Sensing Symposium, 22-27 July 2018, Valencia, Spain.

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Abstract

Long term climate data records are vital for the study of climatic change. Practically, the several-decade observation periods required fall well outside the duration of any single Earth Observation satellite mission. As such, producing suitable datasets from remote sensing data requires the combination of observations from an extended series of a given sensor, these series are known as fundamental climate data records (FCDRs). A goal of the FIDUCEO project is to produce four such FCDRs in a metrologically rigorous manner, for sensor series observing in visible, infrared and microwave spectral domains.
One might naively assume that since all the sensors in a series are calibrated, it is trivial to combine their data into one single record. However, pre-launch and in-flight calibrations from sensor to sensor are inconsistent at levels that are not negligible in terms of their impact on derived geophysical products, preventing their use for characterisation of subtle climatic trends.
Instead we perform a consistent recalibration of all the sensors in a series, in comparison with a modern reference sensor with a high quality calibration, in a process referred to as harmonisation. This involves taking the data from the periods during which sensors operated concurrently and finding instances, known as match-ups, where two sensors simultaneously observe the same location on the Earth with compatible viewing geometry (within a given tolerance). The problem then becomes a non-linear regression problem, solving for new calibration parameters in the measurement equation of each sensor.
It has been found that existing methods to solve this problem do not provide optimal solutions. Instead, we present here the use and validation of a novel, metrologically rigorous approach using both simulated and real data from the AVHRR (Advanced Very High Resolution Radiometer) sensor, which has flown on NOAA and EUMETSAT/MetOp satellite series from 1979 to the present day.

Item Type: Conference or Workshop Item (Paper)
Subjects: Optical Radiation and Photonics > Environment and Climate Change
Divisions: Chemical, Medical & Environmental Science
Identification number/DOI: 10.1109/IGARSS.2018.8518934
Last Modified: 12 Feb 2019 14:30
URI: http://eprintspublications.npl.co.uk/id/eprint/8282

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