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Dataset

 

STFC RAL methane retrievals from IASI on board MetOp-A, version 2.0

Update Frequency: Not Planned
Status: Completed
Online Status: ONLINE
Publication State: Citable
Publication Date: 2020-02-25
DOI Publication Date: 2020-03-10
Download Stats: last 12 months

Abstract

This 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 (water vapour isotopologue) 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 United Kingdom Research and Innnovation (UKRI) Science and Technology Facilities Council (STFC) Remote Sensing Group (RSG) at the Rutherford Appleton Laboratory (RAL).

This is version 2.0 of the dataset.

Citable as:  Siddans, R.; Knappett, D.; Kerridge, B.; Latter, B.; Waterfall, A. (2020): STFC RAL methane retrievals from IASI on board MetOp-A, version 2.0. Centre for Environmental Data Analysis, 10 March 2020. doi:10.5285/f717a8ea622f495397f4e76f777349d1. http://dx.doi.org/10.5285/f717a8ea622f495397f4e76f777349d1
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) at the United Kingdom Research and Innovation (UKRI) Science and Technology Facilities Council (STFC). 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:
Data are as provided by the data providers. See the user guide for further information
File Format:
Data are in NetCDF format.

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 effective cloud fraction.
  • var_id: ap_cloud_fraction
  • units: 1
  • names: A priori effective cloud fraction.
  • long_name: A priori effective cloud-top pressure (hPa)
  • var_id: ap_cloud_pressure
  • units: hPa
  • names: A priori effective cloud-top pressure (hPa)
  • var_id: ap_ch4_xvmr_err
  • long_name: A priori error on retrieved column-averaged dry-air mole fraction of atmospheric methane (ppmv).
  • units: 1e-6
  • names: A priori error on retrieved column-averaged 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).
  • units: W/(m^2*sr*m^-1)
  • var_id: rad_avhrr_tir
  • long_name: AVHRR L1 (tir) radiances in channels 3b, 4 and 5.
  • names: AVHRR L1 (tir) radiances in channels 3b, 4 and 5.
  • long_name: AVHRR L1 (vis/nir/swir) radiances in channels 1, 2 and 3a.
  • units: W/(m^2*sr)
  • var_id: rad_avhrr_vis
  • names: AVHRR L1 (vis/nir/swir) radiances in channels 1, 2 and 3a.
  • long_name: Apriori 13CH4 scaling factor.
  • var_id: ap_ch4iso_sf
  • names: Apriori 13CH4 scaling factor.
  • var_id: ap_hdo_sf
  • long_name: Apriori HDO scaling factor.
  • names: Apriori HDO scaling factor.
  • long_name: Apriori error on 13CH4 scaling factor.
  • var_id: ap_ch4iso_sf_err
  • names: Apriori error on 13CH4 scaling factor.
  • long_name: Apriori error on HDO scaling factor.
  • var_id: ap_hdo_sf_err
  • names: Apriori error on HDO scaling factor.
  • long_name: Averaging kernel for column-averaged mixing ratio (ppmv).
  • var_id: ak_xvmr
  • names: Averaging kernel for column-averaged mixing ratio (ppmv).
  • var_id: ak_vmr
  • long_name: Averaging kernel for profile mixing ratios (ppmv).
  • names: Averaging kernel for profile mixing ratios (ppmv).
  • long_name: Column-averaged equivalent CH4 (modelled).
  • var_id: ch4_xvmr_eql
  • units: 1e-6
  • names: Column-averaged equivalent CH4 (modelled).
  • long_name: Column-averaged equivalent N2O (modelled).
  • var_id: n2o_xvmr_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.
  • long_name: Estimated error on retrieved 13CH4 scaling factor.
  • var_id: ch4iso_sf_err
  • names: Estimated error on retrieved 13CH4 scaling factor.
  • 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 HDO scaling factor.
  • var_id: hdo_sf_err
  • names: Estimated error on the retrieved HDO scaling factor.
  • 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: IMS (pre-retrieval) cloud fraction.
  • var_id: ims_cloud_fraction
  • units: hPa
  • names: IMS (pre-retrieval) cloud fraction.
  • units: hPa
  • long_name: IMS (pre-retrieval) cloud top pressure (hPa).
  • var_id: ims_cloud_pressure
  • names: IMS (pre-retrieval) cloud top pressure (hPa).
  • long_name: IMS (pre-retrieval) retrieval convergence.
  • var_id: ims_conv
  • names: IMS (pre-retrieval) retrieval convergence.
  • long_name: IMS (pre-retrieval) retrieval cost function value (measurement vector component).
  • var_id: ims_jy
  • names: IMS (pre-retrieval) retrieval cost function value (measurement vector component).
  • long_name: IMS (pre-retrieval) retrieval cost function value (state vector component).
  • var_id: ims_jx
  • names: IMS (pre-retrieval) retrieval cost function value (state vector component).
  • var_id: ims_surface_temperature
  • long_name: IMS (pre-retrieval) surface temperature (K).
  • units: K
  • names: IMS (pre-retrieval) surface temperature (K).
  • long_name: Latitude (degrees north).
  • units: degree_north
  • var_id: lat
  • names: Latitude (degrees north).
  • var_id: lon
  • units: degree_east
  • long_name: Longitude (degrees east).
  • names: Longitude (degrees east).
  • long_name: Modelled surface spectral emissivity at selected wavenumbers.
  • units: 1
  • var_id: emis
  • names: Modelled surface spectral emissivity at selected wavenumbers.
  • 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: Off-diagonals of the solution correlation matrix for a subset of retrieval levels (as used for averaging kernels).
  • var_id: ch4_vsx
  • names: Off-diagonals of the solution correlation matrix for a subset of retrieval levels (as used for averaging kernels).
  • 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 13CH4 scaling factor.
  • var_id: ch4iso_sf
  • names: Retrieved 13CH4 scaling factor.
  • 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).
  • var_id: surface_temperature
  • units: K
  • names: 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.
  • long_name: Sensor zenith angle (degrees).
  • var_id: vza
  • units: degree
  • names: Sensor zenith angle (degrees).
  • var_id: sza
  • long_name: Solar zenith angle (degrees).
  • units: degree
  • names: 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).
  • var_id: ims_dt1000
  • long_name: Surface - 1000m air temperature difference
  • units: K
  • names: Surface - 1000m air temperature difference
  • long_name: Surface - 2m air temperature difference
  • var_id: ims_dt2
  • units: K
  • names: Surface - 2m air temperature difference
  • 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.
  • var_id: surface_pressure
  • units: hPa
  • names: 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: ms
  • long_name: Time of day in msec since midnight (UTC).
  • names: Time of day in msec since midnight (UTC).
  • units: cm-1
  • long_name: Wavenumbers for which modelled surface spectral emissivity is provided.
  • var_id: emis_wn
  • names: Wavenumbers for which modelled surface spectral emissivity is provided.
  • long_name: Year.
  • var_id: year
  • names: Year.

Co-ordinate Variables

Coverage
Temporal Range
Start time:
2007-05-31T23:00:00
End time:
2017-12-31T23:59:59
Geographic Extent

 
90.0000°
 
-180.0000°
 
180.0000°
 
-90.0000°