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Dataset

 
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STFC RAL methane retrievals from IASI on board MetOp-A, version 1.0

Update Frequency: Not Planned
Status: Completed
Online Status: ONLINE
Publication State: Citable
Publication Date: 2016-03-17
DOI Publication Date: 2016-03-18
Download Stats: last 12 months

This dataset has been superseded. See Latest Version here
Abstract

The Infrared Atmospheric Sounding Interferometer (IASI) methane dataset contains height-resolved and column-averaged volume mixing ratios of atmospheric methane (CH4). It also includes column-averaged water vapour (H2O), a scale factor for the HDO volume mixing ratio profile, surface temperature, effective cloud fraction, effective cloud-top pressure and scale factors for two systematic residual spectra which are jointly retrieved from the spectral range 1232.25-1290.00 cm-1 by the Rutherford Appleton Laboratory (RAL) IASI optimal estimation methane retrieval scheme. The dataset additionally contains selected a priori values and uncertainties adopted in the optimal estimation scheme and retrieval output diagnostics such as the retrieval cost and the averaging kernels.

This work was funded by the National Centre for Earth Observation (NCEO) under the UK Natural Environment Research Council (NERC) with additional funding from EUMETSAT.

Data were produced by the Science and Technology Facilities Council (STFC) Remote Sensing Group (RSG) at the Rutherford Appleton Laboratory (RAL).

This is version 1.0 of this dataset and is the first to be released.

Citable as:  Siddans, R.; Knappett, D.; Kerridge, B.; Latter, B.; Waterfall, A.; Hurley, J.; Walker, J. (2016): STFC RAL methane retrievals from IASI on board MetOp-A, version 1.0. Centre for Environmental Data Analysis, 18 March 2016. doi:10.5285/B6A84C73-89F3-48EC-AEE3-592FEF634E9B. http://dx.doi.org/10.5285/B6A84C73-89F3-48EC-AEE3-592FEF634E9B
Abbreviation: Not defined
Keywords: methane, IASI, optimal estimation, retrieval, averaging kernels, assimilation

Details

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Use of these data is covered by the following licence: http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/. When using these data you must cite them correctly using the citation given on the CEDA Data Catalogue record.
Data lineage:

Data produced by the Rutherford Appleton Laboratory (RAL) Remote Sensing Group (RSG). The development of the Infrared Atmospheric Sounding Interferometer (IASI) offline thermal-IR methane retrieval was funded by the Natural Environment Research Council (NERC) through its National Centre for Earth Observation (NCEO) with additional funding from EUMETSAT.

Data Quality:
See dataset associated documentation.
File Format:
Files are formatted in netCDF4.

Process overview

This dataset was generated by a combination of instruments deployed on platforms and computations as detailed below.

Instrument/Platform pairings

IASI Deployed on: Metop-A

Mobile platform operations

Mobile Platform Operation 1 Mobile Platform Operation for: Metop-A

Computation Element: 1

Title STFC RAL IASI methane processor
Abstract Retrieval of methane using the STFC RAL IASI methane processor. Full retrieval diagnostic information including averaging kernels, estimated error and retrieved cloud parameters.
Input Description None
Output Description None
Software Reference None
Output Description None
  • long_name: A priori column-averaged dry-air mole fraction of atmospheric methane (ppmv).
  • var_id: ap_ch4_xvmr
  • units: 1e-6
  • names: A priori column-averaged dry-air mole fraction of atmospheric methane (ppmv).
  • var_id: ap_ch4_vmr
  • units: 1e-6
  • long_name: A priori dry-air mole fraction of atmospheric methane (ppmv).
  • names: A priori dry-air mole fraction of atmospheric methane (ppmv).
  • long_name: A priori error on retrieved dry-air mole fraction of atmospheric methane (ppmv).
  • var_id: ap_ch4_vmr_err
  • units: 1e-6
  • names: A priori error on retrieved dry-air mole fraction of atmospheric methane (ppmv).
  • long_name: A priori surface temperature (K).
  • var_id: ap_surface_temperature
  • units: K
  • names: A priori surface temperature (K).
  • long_name: Averaging kernel for column-averaged mixing ratio (ppmv).
  • var_id: ak_xvmr
  • units: 1e-6
  • names: Averaging kernel for column-averaged mixing ratio (ppmv).
  • var_id: ak_vmr
  • units: 1e-6
  • long_name: Averaging kernel for profile mixing ratios (ppmv).
  • names: Averaging kernel for profile mixing ratios (ppmv).
  • long_name: Column-averaged equivalent N2O (modelled).
  • var_id: xn2o_eql
  • units: 1e-6
  • names: Column-averaged equivalent N2O (modelled).
  • var_id: day
  • long_name: Day of the month (1-31).
  • names: Day of the month (1-31).
  • long_name: Errors on residual scale factors.
  • var_id: rsf_err
  • names: Errors on residual scale factors.
  • units: 1e-6
  • long_name: Estimated error on retrieved methane profile (ppmv).
  • var_id: ch4_vmr_err
  • names: Estimated error on retrieved methane profile (ppmv).
  • long_name: Estimated error on the retrieved column-averaged mixing ratio (ppmv).
  • var_id: ch4_xvmr_err
  • units: 1e-6
  • names: Estimated error on the retrieved column-averaged mixing ratio (ppmv).
  • long_name: Flag indicating retrieval convergence (1=fully converged). Results with other values should be used with more caution.
  • var_id: conv
  • names: Flag indicating retrieval convergence (1=fully converged). Results with other values should be used with more caution.
  • var_id: pixel_number
  • long_name: IASI detector pixel (0-3).
  • names: IASI detector pixel (0-3).
  • long_name: Month of the year (1-12).
  • var_id: month
  • names: Month of the year (1-12).
  • long_name: Number of scan line (0=start of orbit).
  • var_id: scan_line
  • names: Number of scan line (0=start of orbit).
  • long_name: Position within scan line (0-29).
  • var_id: scan_position
  • names: Position within scan line (0-29).
  • units: hPa
  • long_name: Pressure levels of true state in provided averaging kernels.
  • var_id: mod_plev
  • names: Pressure levels of true state in provided averaging kernels.
  • var_id: ret_plev_ak
  • units: hPa
  • long_name: Pressures of retrieval levels (hPa) for which averaging kernels are provided.
  • names: Pressures of retrieval levels (hPa) for which averaging kernels are provided.
  • long_name: Retrieval cost function value.
  • var_id: chim
  • names: Retrieval cost function value.
  • long_name: Retrieval pressure levels (hPa).
  • var_id: ret_plev
  • units: hPa
  • names: Retrieval pressure levels (hPa).
  • long_name: Retrieved HDO scaling factor (effective HDO amount compared to Hitran assumed ratio of HDO to main water vapour isotope).
  • var_id: hdo_sf
  • names: Retrieved HDO scaling factor (effective HDO amount compared to Hitran assumed ratio of HDO to main water vapour isotope).
  • var_id: ch4_xvmr
  • units: 1e-6
  • long_name: Retrieved column-averaged dry-air mole fraction of atmospheric methane (ppmv).
  • names: Retrieved column-averaged dry-air mole fraction of atmospheric methane (ppmv).
  • long_name: Retrieved column-averaged mole fraction of atmospheric water vapour in air (ppmv).
  • var_id: h2o_xvmr
  • units: 1e-6
  • names: Retrieved column-averaged mole fraction of atmospheric water vapour in air (ppmv).
  • long_name: Retrieved dry-air mole fraction of atmospheric methane (ppmv).
  • var_id: ch4_vmr
  • units: 1e-6
  • names: Retrieved dry-air mole fraction of atmospheric methane (ppmv).
  • units: 1
  • long_name: Retrieved effective cloud fraction.
  • var_id: cloud_fraction
  • names: Retrieved effective cloud fraction.
  • units: hPa
  • long_name: Retrieved effective cloud-top pressure (hPa).
  • var_id: cloud_pressure
  • names: Retrieved effective cloud-top pressure (hPa).
  • long_name: Retrieved surface temperature (K).
  • standard_name: surface_temperature
  • var_id: surface_temperature
  • units: K
  • names: surface_temperature, Retrieved surface temperature (K).
  • long_name: Scale factors for the mean fit and across-track residual patterns.
  • var_id: rsf
  • names: Scale factors for the mean fit and across-track residual patterns.
  • units: degrees
  • long_name: Sensor zenith angle (degrees).
  • var_id: vza
  • standard_name: sensor_zenith_angle
  • names: sensor_zenith_angle, Sensor zenith angle (degrees).
  • standard_name: solar_zenith_angle
  • var_id: sza
  • long_name: Solar zenith angle (degrees).
  • units: degrees
  • names: solar_zenith_angle, Solar zenith angle (degrees).
  • units: km
  • long_name: Spatially interpolated ECMWF surface altitude (km).
  • var_id: ecmwf_alt
  • names: Spatially interpolated ECMWF surface altitude (km).
  • long_name: Surface Temperature
  • names: Surface Temperature
  • long_name: Surface altitude (km) corresponding to IASI measurement, based on averaging GTOPO30 to 12km resolution and sampling every 0.05 degrees.
  • var_id: iasi_alt
  • units: km
  • names: Surface altitude (km) corresponding to IASI measurement, based on averaging GTOPO30 to 12km resolution and sampling every 0.05 degrees.
  • long_name: Surface pressure (hPa) used in the retrieval.
  • standard_name: surface_air_pressure
  • units: hPa
  • var_id: surface_pressure
  • names: surface_air_pressure, Surface pressure (hPa) used in the retrieval.
  • long_name: The average number of retrieval steps (number of calls to the forward model).
  • var_id: nstep
  • names: The average number of retrieval steps (number of calls to the forward model).
  • long_name: The brightness temperature difference (K) at 12 microns between observations and simulations (based on ECMWF data). Used to initially screen observations for cloud.
  • var_id: bt_diff
  • units: K
  • names: The brightness temperature difference (K) at 12 microns between observations and simulations (based on ECMWF data). Used to initially screen observations for cloud.
  • var_id: time_in_msec
  • units: msec
  • long_name: Time of day in msec since midnight (UTC).
  • names: Time of day in msec since midnight (UTC).
  • long_name: Year.
  • var_id: year
  • names: Year.

Co-ordinate Variables

  • standard_name: latitude
  • var_id: lat
  • units: degrees_north
  • long_name: Latitude (degrees_north)
  • names: latitude, Latitude (degrees_north)
  • var_id: lon
  • units: degrees_east
  • standard_name: longitude
  • long_name: Longitude (degrees east).
  • names: longitude, Longitude (degrees east).
Coverage
Temporal Range
Start time:
2007-05-31T23:00:00
End time:
2016-12-31T23:59:59
Geographic Extent

 
90.0000°
 
-180.0000°
 
180.0000°
 
-90.0000°