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| SAPHIR | |
|---|---|
| Name | SAPHIR |
| Type | Atmospheric sounding instrument |
| Developer | Météo-France / CNES |
| Introduced | 2000s |
| Applications | Atmospheric sounding, meteorology, climate research |
| Platform | Meteorological satellites, research aircraft |
SAPHIR
SAPHIR is a satellite- and aircraft-borne atmospheric sounding instrument developed for humidity and temperature profiling in support of meteorology, climatology, numerical weather prediction, and atmospheric chemistry studies. It was designed and deployed through collaborations among Météo-France, the CNES, and international partners including EUMETSAT and national meteorological services such as Météo-France and Met Office. The instrument has contributed data to initiatives like the ECMWF, the WMO, and regional observational networks.
SAPHIR provides limb- and nadir-sounding measurements of water-vapour and temperature by observing specific microwave and infrared absorptions, supplementing measurements from missions such as NOAA polar satellites, Metop series, and the Aqua satellite. Its data streams are assimilated into reanalysis projects like ERA-Interim and ERA5, and used by research programmes including GCOS, SPARC, and IGAC. Instrument teams coordinate with agencies such as NASA, JAXA, and ESA for calibration, validation, and cross-comparison against radiosonde networks and ground-based facilities like GRUAN sites and microwave radiometer arrays.
Development of the instrument traces to requirements articulated in the 1990s by WMO and European meteorological agencies to improve humidity profiling above the planetary boundary layer and in the upper troposphere and lower stratosphere. Early prototype work involved partnerships between Météo-France, CNES, academic groups at institutions like LMD (Laboratoire de Météorologie Dynamique), and industrial contractors that also worked on projects for Thales Alenia Space and Airbus Defence and Space. Flight-demonstration campaigns used aircraft platforms such as the F-20, HALO, and research flights coordinated with field campaigns like EUCAARI and ARISTO. Operational adoption was influenced by successful validation against radiosonde ascents, GPS radio occultation records from COSMIC, and limb-sounding data from missions like UARS and ACE.
SAPHIR employs a multi-channel radiometer/spectrometer architecture optimized for absorption lines of water vapour and related species; design work leveraged heritage from instruments on MetOp and IASI development. Primary components include stabilized microwave receivers, infrared detectors cooled with cryogenic systems similar to those on HIRS and MIPAS, scanning optics, and on-board calibration targets derived from designs used by MODIS teams. The instrument’s spectral channels are selected to sample atmospheric layers from the lower troposphere to the lower stratosphere, matching vertical resolution targets set by WMO observing systems. Data formats conform to community standards used by EUMETSAT and NOAA operational processing pipelines, and processing chains interface with centers like ECMWF and ECMWF Reanalysis nodes for level-1 and level-2 product generation.
SAPHIR instruments have flown on satellite platforms managed by CNES and operated in coordination with EUMETSAT ground segments, and have been deployed on research aircraft during coordinated campaigns by organizations such as ESA and NCAR. Operational deployments involve pre-launch calibration at facilities used by CNES and inter-calibration with sensors on Metop, NOAA, and Suomi NPP. Data latency options have been tailored for both real-time assimilation by centers like ECMWF and retrospective analysis by projects such as CMIP model evaluation. Field deployments included synergies with balloon-borne programmes managed by CNES and international sounding networks administered through WMO.
Datasets from SAPHIR support tropospheric humidity monitoring for short-term forecasting at centers including ECMWF and Météo-France, climate trend analysis used by IPCC assessment teams, and process studies in programs like SPARC and WCRP. Applications extend to aviation safety collaborations with organizations such as ICAO for turbulence and icing risk assessment, to air-quality modelling groups including EMEP and regional forecasting consortia. Validation and intercomparison studies have involved satellite missions like AIRS, CrIS, and IASI, as well as ground truth from radiosonde and lidar networks operated by institutions such as NOAA and LSCE.
SAPHIR is often compared with instruments such as AIRS on Aqua, CrIS on Suomi NPP, IASI on Metop, and microwave sounders on NOAA platforms. Relative advantages include optimized humidity retrievals in the upper troposphere compared with sounders primarily designed for temperature profiling; trade-offs parallel discussions surrounding hyperspectral infrared versus microwave limb-sounding architectures seen in missions like MIPAS and MLS. Variants and follow-on concepts have been proposed by consortia including ESA and EUMETSAT to integrate with constellation concepts exemplified by Metop-SG and collaborative programmes like Jason and Copernicus.
Planned evolutions of the SAPHIR concept focus on higher spectral resolution, improved radiometric stability, and integration into multi-sensor constellations coordinated by EUMETSAT, ESA, and national agencies such as CNES and NASA. Proposals consider synergy with GPS radio occultation constellations like COSMIC-2, combined retrieval frameworks used by ECMWF and reanalysis initiatives like ERA5C, and enhanced calibration strategies drawing on reference sites in the GRUAN network. Technology roadmaps reference advances developed for missions including MTG and Metop-SG to improve vertical resolution, data latency, and utility for both operational forecasting and climate monitoring.
Category:Atmospheric sounding instruments