Abstract
We investigate three key aspects for creating a climate record from multiple hyperspectral infra-red sensors. The motivation is to produce a multi-decade continuous record of global radiance measured leaving the atmosphere. Current global observation mission scenarios aim to supply multiple follow-on missions for the JPSS CrIS and MetOp IASI sensors which, in addition to the current Aqua AIRS sensor, could in principle provide a continuous radiance record from 2002 to 2025 and beyond. We aim to apply this record to studies of climate trends directly from the radiance and also to a common set of geophysical quantities using retrieval methods that share a common radiative transfer model.
The three sensors being used in this study; Aqua AIRS, NOAA CrIS and MetOp IASI share some similar characteristics; they are all low-earth, high inclination sun-synchronous polar orbiters and hyperspectral infra-red mapping missions. Deriving a common radiance record requires methods to relate their spectral capabilities, their radiometric calibration and their spatial-temporal mapping characteristics. We detail (i). a method to translate the spectral radiance measurements onto a common graduated scale, or line-shape, (ii) how to calibrate their radiometric scale and (iii) how to deal with spatial and temporal coherence differences of their global sampling.
Considerable mission overlaps of these sensors are used to make direct inter-comparisons between sensors using simultaneous nadir observations and large sample statistical methods. One of the key goals is to be able to maintain relative stability to about 10 mK per year over the long term, and in this paper we will show how this might be possible.
We demonstrate the performance of this approach by comparing top-of atmosphere radiance trends from simulations using the ECMWF ERA reanalysis, which is presently the most popular measurement-based climate data set used by the scientific community.
Creating a Single Radiance Climate Record from AIRS, IASI and CrIS
We investigate three key aspects for creating a climate record from multiple hyperspectral infra-red sensors. The motivation is to produce a multi-decade continuous record of global radiance measured leaving the atmosphere. Current global observation mission scenarios aim to supply multiple follow-on missions for the JPSS CrIS and MetOp IASI sensors which, in addition to the current Aqua AIRS sensor, could in principle provide a continuous radiance record from 2002 to 2025 and beyond. We aim to apply this record to studies of climate trends directly from the radiance and also to a common set of geophysical quantities using retrieval methods that share a common radiative transfer model.
The three sensors being used in this study; Aqua AIRS, NOAA CrIS and MetOp IASI share some similar characteristics; they are all low-earth, high inclination sun-synchronous polar orbiters and hyperspectral infra-red mapping missions. Deriving a common radiance record requires methods to relate their spectral capabilities, their radiometric calibration and their spatial-temporal mapping characteristics. We detail (i). a method to translate the spectral radiance measurements onto a common graduated scale, or line-shape, (ii) how to calibrate their radiometric scale and (iii) how to deal with spatial and temporal coherence differences of their global sampling.
Considerable mission overlaps of these sensors are used to make direct inter-comparisons between sensors using simultaneous nadir observations and large sample statistical methods. One of the key goals is to be able to maintain relative stability to about 10 mK per year over the long term, and in this paper we will show how this might be possible.
We demonstrate the performance of this approach by comparing top-of atmosphere radiance trends from simulations using the ECMWF ERA reanalysis, which is presently the most popular measurement-based climate data set used by the scientific community.