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RELEVANCE OF MISSIONS IN THE CGMS BASELINE TO SUPPORT THE GCOS ESSENTIAL CLIMATE VARIABLES (ECVs),
AND SPECIFICATION OF FUNDAMENTAL CLIMATE DATA RECORDS (FCDRs)
1st March 2014
1. Introduction - Purpose of the study
In the past years, the Coordination Group for Meteorological satellites (CGMS) has defined a strategy for missions to be maintained, developed and sustained for the operational meteorological community and associated communities. The current list of these missions is tabled as follows.
Missions currently in the CGMS baseline (as of March 2014)GEO / Advanced VIS/IR imagery / LEO / IR hyper-spectral sounders / Broadband VIS/IR radiometer
GEO / IR Sounding (hyperspectral on some locations) / LEO / MW sounders / Total solar irradiance sensor
GEO / Lightning detection / MW imagers - some polarimetric / Atmospheric composition (contribution)
GEO / Earth radiation budget / Scatterometers / Narrow-band VIS/NIR imagers (ocean colour and vegetation)
GEO / High spectral resolution UV sounding / Altimeter constellation / High-resolution multi-spectral VIS/IR imagers
LEO / Multispectral VIS/IR imagery / Radio occultation / IR dual-angle view imager
The purpose of this study is to assess the relevance of these missions for supporting the Essential Climate Variables (ECV) defined for the Global Climate Observing System (GCOS). The current list of ECVs (see http://gosic.org/ios/MATRICES/ECV/ECV-matrix.htm) is tabled as follows
GCOS Essential Climate Variables (ECV) (as of 23 January 2013)ATMOSPHERIC (over Land, Sea & Ice) / OCEANIC / TERRESTRIAL
Surface / Surface / River Discharge
Surface Air Pressure / Carbon Dioxide Partial Pressure / Water Use
Surface Air Temperature / Current / Ground Water
Surface Precipitation / Ocean Acidity / Lakes
Surface Radiation Budget / Ocean Colour / Snow Cover
Water Vapour (Surface humidity) / Phytoplankton / Glaciers and Ice Caps
Near-Surface Wind Speed and Direction / Sea Ice / Permafrost and seasonally frozen ground
Upper-Air / Sea Level / Albedo and Reflectance Anisotropy
Cloud Properties / Sea State / Land Cover (including Vegetation Type)
Earth Radiation Budget (including Solar Irradiance) / Sea Surface Salinity / FAPAR
Temperature / Sea Surface Temperature / Leaf Area Index (LAI)
Water Vapour / Sub-Surface / Above Ground Biomass
Wind Speed and Direction / Carbon / Fire Disturbance
Composition / Current / Soil Moisture
Carbon Dioxide / Nutrients / Soil Carbon
Methane / Ocean Acidity / Ice Sheets
Other Long-Lived Greenhouse Gases: / Oxygen
N2O / SF6 / CFCs / HCFCs / HFCs / PFCs / Salinity
Ozone and Aerosols / Temperature
Precursors (supporting the Aerosols and Ozone ECVs): / Tracers
NO2 / SO2 / CO / HCHO / Global Ocean Heat Content
The colours In the table above indicate the capability of satellites to provide useful contribution. Colour green indicates consolidated or potential contribution. Colour orange indicates null or unlikely contribution in any foreseeable future [that does not exclude that certain partial aspects of the ECV may draw benefit from satellite observation]. Colour yellow indicates that the current definition is too general: if split in more components, it could be found that several draw benefit from satellites.
The objective of this study is to identify Fundamental Climate Data Records (FCDR) that the CGMS baseline missions can provide in support of the ECVs. According to the GCOS definition, the term “Fundamental Climate Data Record” (FCDR) denotes a well-characterized, long-term data record, usually involving a series of instruments, with potentially changing measurement approaches, but with overlaps and calibrations sufficient to allow the generation of products that are accurate and stable in both space and time to support climate applications [from Report GCOS-154 “Systematic observation requirements for satellite-based data products for climate” dated December 2011, available at http://www.wmo.int/pages/prog/gcos/Publications/gcos-154.pdf].
The study is performed on the base of the information collected in the WMO “Observing Systems Capability Analysis and Review Tool” (OSCAR, accessible at http://www.wmo-sat.info/oscar/spacecapabilities). The FCDR are identified on the base of actual instruments as described in OSCAR. The following have been considered:
- all current and planned satellites and instruments
- satellites/instruments that were still active in 1990 or shortly before, many of which belonging to series active since the early 1980’s or before.
The study considers the satellites/instruments belonging to the CGMS baseline, that includes systems of different nature:
- operational: long-term continuity committed, generally by meteorological agencies
- continuous: programmes not formally committed, but in practice carried out for long-term, through by evolving technological systems
- R&D: not committed for long-term continuity, generally run by R&D space agencies.
The full set of identified FCDRs, with the list of relevant instruments and summary description of their main characteristics, is provided as an Annex excel file. For more detailed instrument characteristics, the reader can access OSCAR and write the instrument name in the “Quick Search” window. It is important to note that the instrument descriptive page includes the list of potentially retrievable variables, together with short information on operational limitations if any.
The tables that follow in this text, extracted from the Annex, record all except the lists of instruments. In the initial columns, under the name of the ECV, mention is given of the FCDRs listed in GCOS-154 report (rather generic, indeed). After the FCDR specific features, there is notion of the performance criteria leading to the nominal FCDR, often split into a few categories: basic, enhanced, optimum, fallback, and others.
Although the study should be limited to the CGMS baseline missions, for the sake of completeness the review is extended to missions not included in the current CGMS baseline. These are listed in the following table.
Missions included in this analysis but not in the current CGMS baselineMission (included in OSCAR) / Relevant to ECV
Space lidar / Upper-air Wind Speed and Direction
Cloud properties, Aerosol, CO2, CH4, O3
Sea ice, Ice sheets, Glaciers, Biomass
Limb-scanning sounder / Upper-air Temperature and Wind Speed and Direction; Aerosol
Cloud and precipitation radar / Cloud Properties, Surface Precipitation
Imaging radar (SAR) / Sea State, Sea Ice
Soil Moisture, Permafrost, Fire, Land Cover, Biomass
Snow Cover, Ice sheets, Glaciers
Positioning system / Near-Surface Wind Speed and Direction
Some of these missions (SAR, positioning) are supported by well-established communities on which CGMS can rely for collaboration, without having to be directly committed. Some (space lidar) are still in a demonstration phase, immature for entering a baseline. Some (limb-scanning, cloud/precipitation radar) are on the boundary.
2. List of FCDRs
The following tables report the list of FCDRs that could be supported by the CGMS baseline, with also mention of systems not in the baseline (gray-shadowed). For the list of instruments and satellites, see the excel file in Annex. For instrument descriptions, including the list of potentially retrievable variables, see OSCAR. Three tables are following, for Atmospheric, Oceanic and Terrestrial ECVs, respectively.
Atmospheric ECVs / Earth Radiation Budget (including Solar Irradiance) / Carbon dioxide (CO2)Upper-air temperature / Surface radiation budget / Formaldehyde (HCHO) (4)
Upper-air water vapour / Water vapour (H2O) (2) / Nitrous oxide (N2O) (3)
Upper-air Wind Speed and Direction / Ozone (O3) (1) / Nitrogen dioxide (NO2) (4)
Near-Surface Wind Speed and Direction / Trichlorofluoromethane (CFC-11) (3) / Sulphur hexafluoride (SF6) (3)
Cloud Properties / Dichlorodifluoromethane (CFC-12) (3) / Sulphur dioxide (SO2) (4)
Surface Precipitation / Methane (CH4)
Aerosol (1) / Carbon monoxide (CO) (4)
(1) Aerosol and ozone split from ECV "Ozone and Aerosol"
(2) H2O separated from ECV "Upper-air water vapour"
(3) CFC-11, CFC-12, N2O and SF6 are part of ECV "Other Long-Lived Greenhouse Gases" - [HCFCs, HFCs and PFCs non considered]
(4) CO, HCHO, NO2 and SO2 are the ingredients of ECV "Precursors (supporting the Aerosols and Ozone ECVs)"
ID / GCOS ECV and FCDR / CGMS baseline / ID / FCDR specific features / ID / Performance criteria1. / Upper-air temperature
FCDR from GCOS-154
- Passive microwave and IR radiances
- GNSS radio occultation bending angles / LEO / IR hyper-spectral sounders / 1.1 / IR spectra to cover the CO2 bands 4-5 mm and 13-15 mm
- Resolving power l/Dl > 1000
- Radiometric accuracy NEDT < 0.2 K @ 280 K / 1.1.1 / Baseline: IR spectra to cover the CO2 bands in MWIR and TIR
- The high spectral resolution provides high vertical resolution of the retrieved variable
- The TIR band is more sensitive to mid- and high layers
- The MWIR band is more sensitive to the lower troposphere
1.1.2 / Fallback: IR spectra to cover the CO2 band in TIR
- Missing sensitivity to the lower troposphere
1.1.3 / Extreme fallback: radiometer instead of spectrometer
- Coarse vertical resolution due to poor spectral resolution
GEO / IR Sounding (hyperspectral on some locations) / 1.2 / Frequent IR spectra to cover the CO2 bands 4-5 mm and 13-15 mm
- Resolving power l/Dl > 1000
- Radiometric accuracy NEDT < 0.2 K @ 280 K
- Image cycle < 30 min / 1.2.1 / Baseline: IR spectra to cover the CO2 bands in MWIR and TIR
- The high spectral resolution provides high vertical resolution of the retrieved variable
- Frequent observation of the temperature (and humidity) profile enables stability change monitoring
1.2.2 / Fallback: IR radiometry in about 20 narrow channels including the CO2 bands in MWIR and TIR
- Coarse vertical resolution due to poor spectral resolution
LEO / MW sounders / 1.3 / MW radiances for fine coverage of the O2 band(s) 50-60 GHz and possibly ~118 GHz
- Well over 10 very-narrow channels in the 50-60 GHz band, less in the 118 GHz band
- Radiometric accuracy NEDT < 0.2 K, SNR > 100
- Supporting channels around 23 GHz (water vapour), and 37 and 90 GHz (windows) / 1.3.1 / Basic: 10 to 15 channels in the O2 band 50-60 GHz, with supporting channels for water vapour correction (~23 GHz) and in window regions (~37 and ~90 GHz)
- For nearly-all-weather temperature sounding
1.3.2 / Alternative: exploitation of the O2 band around 118 GHz, with supporting water vapour and window channels
- More sensitive to the higher atmospheric layers
- More affected by clouds, especially ice
1.3.3 / Optimum: both O2 bands 50-60 GHz and ~118 GHz exploited, with supporting water vapour and window channels
- Improved vertical resolution of the retrieved variable
Radio occultation / 1.4 / Sequence of the measurements of the bending angle of the signal received at the LEO in respect of the line-of sight LEO - GNSS satellite
- Capability of tracking both rising occultations (fore-) and setting (aft-)
- Capability of capturing signals from more constellations of the GNSS system
- Mission possibly implemented by more satellites in a dedicated constellation
- Two frequencies needed for ionospheric correction (and possible observation)
- Supported by a network of fiducial ground stations / 1.4.1 / Basic: capability to track the satellites of one constellation of the GNSS system during occultation
- Capability to capture 200 to 700 events/day, depending on whether tracking is performed both fore- and aft- or only fore- or aft
1.4.2 / Enhanced: capability of exploiting more GNSS constellations (GPS, GLONASS, Galileo, Beidou)
- Larger number of captured events (~1,000 to ~2,500 per day) with 2 or 3 constellation systems utilised for tracking
1.4.3 / Optimum: implementation of the mission by a dedicated constellation of microsatellites
- Much larger number of captured events (~2,500 to ~10,000 per day) depending on the number of tracked systems
Limb-scanning sounder
[not in the current baseline] / 1.5 / Spectral data in short-wave or infrared or millimetre-submillimetre wave collected from the limb of the atmosphere
- Scanning sampling driven to determine a vertical resolution of 2-3 km
- Scattered or emitted radiation from the lines of atmospheric constituents, or missing lines from the solar spectrum because of absorption in the occultation geometry / 1.5.1 / Line broadening in short-wave spectroscopy
- High vertical resolution in the upper atmosphere
1.5.2 / Line broadening in IR spectroscopy
- High vertical resolution in the upper atmosphere
1.5.3 / Line broadening in Millimetre-submillimetre wave spectroscopy
- Capability to scan the upper troposphere in addition to the upper atmosphere
1.5.4 / Line broadening in short-wave spectroscopy in star occultation
- Self-calibrating capability. Coverage extended to all latitudes
1.5.5 / Line broadening in short-wave spectroscopy in solar occultation
- Self-calibrating capability. Coverage limited to latitudes determined by the orbital inclination
1.5.6 / Line broadening in IR spectroscopy in solar occultation
- Self-calibrating capability. Coverage limited to latitudes determined by the orbital inclination
2. / Upper-air water vapour
FCDR from GCOS-154:
- Passive microwave radiances
- UV/VIS imager radiances
- IR and microwave radiances
- Limb soundings / LEO / IR hyper-spectral sounders / 2.1 / IR spectra to cover the H2O bands 5-8 mm and possibly 13-20 mm
- Resolving power l/Dl > 1000
- Radiometric accuracy NEDT < 0.2 K @ 280 K / 2.1.1 / Basic: IR spectra to cover the H2O band in MWIR and TIR
- The high spectral resolution provides high vertical resolution of the retrieved variable
2.1.2 / Enhanced: spectral range extended to FIR
- The Far Infrared is sensitive to the higher troposphere
2.1.3 / Extreme fallback: radiometer instead of spectrometer
- Coarse vertical resolution due to poor spectral resolution
GEO / IR Sounding (hyperspectral on some locations) / 2.2 / Frequent IR spectra to cover the H2O band 5-8 mm
- Resolving power l/Dl > 1000
- Radiometric accuracy NEDT < 0.2 K @ 280 K
- Image cycle < 30 min / 2.2.1 / Baseline: IR spectra to cover the H2O band in MWIR/TIR
- The high spectral resolution provides high vertical resolution of the retrieved variable
- Frequent observation of water-vapour (and temperature) profile enables stability change monitoring
2.2.2 / Fallback: IR radiometry in about 20 narrow channels including the H2O band in MWIR/TIR
- Coarse vertical resolution due to poor spectral resolution
LEO / MW sounders / 2.3 / MW radiances for fine coverage of the H2O band around 183 GHz
- 3 to 6 channels in the 183 GHz band, and supporting windows at ~90 and ~160 GHz
- Radiometric accuracy NEDT < 1 K, SNR > 100