Multi-Sensor Calibration Studies of AVHRR-Heritage Channel Radiances Using the Simultaneous Nadir Observation Approach

Karl-Göran Karlsson,Erik Johansson

doi:10.3390/rs6031845

Abstract

The European Space Agency project for studies of cloud properties in the Climate Change Initiative programme (ESA-CLOUD-CCI) aims at compiling the longest possible time series of cloud products from one single multispectral sensor—The five-channel Advanced Very High Resolution Radiometer (AVHRR) instrument. A particular aspect here is to include corresponding products based on other existing (Moderate Resolution Imaging Spectroradiometer (MODIS), Advanced Along-Track Scanning Radiometer (AATSR), MEdium Resolution Imaging Spectrometer (MERIS), Visible and Infrared Radiometer Suite (VIIRS)) and future Sea and Land Surface Temperature Radiometer (SLSTR) sensors measuring in similar (AVHRR-heritage) spectral channels. Initial inter-comparisons of the involved AVHRR-heritage channel radiances over a short demonstration period (2007–2009) were performed. Using Aqua-MODIS as reference, AVHRR (NOAA-18), AATSR, and MERIS channel radiances were evaluated using the simultaneous nadir (SNO) approach. Results show generally agreeing radiances within approximately 3% for channels at 0.6 µm and 0.8 µm. Larger deviations (+5%) were found for the corresponding AATSR channel at 0.6 µm. Excessive deviations but with opposite sign were also indicated for AATSR 1.6 µm and MERIS 0.8 µm radiances. Observed differences may largely be attributed to residual temporal and spatial matching differences while excessive AATSR and MERIS deviations are likely partly attributed to incomplete compensation for spectrally varying surface and atmospheric conditions. However, very good agreement was found for all infrared channels among all the studied sensors. Here, deviations were generally less than 0.2% for the measured brightness temperatures with the exception of some remaining non-linear deviations at extreme low and high temperatures.

Highlights

The task of creating climatologies of different atmospheric and surface parameters from satellite measurements has, far, been limited by the fact that most satellite sensors have not been available over a sufficiently long time to be able to provide climatologically significant data records
This paper describes the initial work in European Space Agency (ESA)-CLOUD-Climate Change Initiative (CCI) concerning the attempts to evaluate the differences between Advanced Very High Resolution Radiometer (AVHRR) radiances and radiances from a set of sensors all having AVHRR-like channels, namely the Moderate Resolution Imaging Spectroradiometer (MODIS), the Advanced
It is clear that conditions for inter-comparisons are quite different for the sensors being in the same orbital plane as MODIS-AQUA (AVHRR) compared to those being in a perpendicular orbital plane (AATSR, MEdium Resolution Imaging Spectrometer (MERIS))

Summary

Introduction

The task of creating climatologies of different atmospheric and surface parameters from satellite measurements has, far, been limited by the fact that most satellite sensors have not been available over a sufficiently long time to be able to provide climatologically significant data records. In this context, it is generally required that a time series of observations should have a length of at least 30 years. A threat against the future prolongation of this observation series for continued use for climate monitoring is the fact that the last AVHRR sensor is soon to be launched on the European Organisation for the Exploitation of Meteorological Satellites EUMETSAT satellite Metop-3 (with tentative launch year 2018).

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