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Dataset

 

Sentinel 5P: Methane (CH4) Total Column level 2 data

Latest Data Update: 2023-03-16
Status: Ongoing
Online Status: ONLINE
Publication State: Published
Publication Date: 2022-11-14
Download Stats: last 12 months
Dataset Size: 53.86K Files | 1TB

Abstract

This dataset contains level 2 (geolocated) total column Methane (CH4) data from the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Sentinel 5P satellite.

Sentinel 5 Precursor (S5P) was launched on the 13th October 2017 carrying TROPOMI. Methane (CH4) is an important atmospheric trace gas for our understanding of tropospheric chemistry. TROPOMI aims at providing CH4 column concentrations with high sensitivity to the Earth’s surface, good spatiotemporal coverage, and sufficient accuracy to facilitate inverse modeling of sources and sinks. TROPOMI uses absorption information from the Oxygen-A Band (760nm) and the SWIR spectral range to monitor CH4 abundances in the Earth's atmosphere.

The Sentinel-5 Precursor mission flies in loose formation (about 3.5 – 5 minutes behind) with the S-NPP (SUOMI-National Polar-orbiting Partnership) mission to use VIIRS (Visible Infrared Imaging Radiometer Suite) cloud information to select cloud-free TROPOMI pixels for high quality methane retrieval.

Citable as:  Copernicus; European Space Agency (2022): Sentinel 5P: Methane (CH4) Total Column level 2 data. NERC EDS Centre for Environmental Data Analysis, date of citation. https://catalogue.ceda.ac.uk/uuid/b33ec61670644124ab4af661009ec507
Abbreviation: Not defined
Keywords: Sentinel, Methane, CH4, TROPOMI

Details

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Use of these data is covered by the following licence: https://sentinel.esa.int/documents/247904/690755/Sentinel_Data_Legal_Notice. When using these data you must cite them correctly using the citation given on the CEDA Data Catalogue record.
Data lineage:

Data collected and prepared by European Space Agency (ESA). Downloaded from the Collaborative Hub for use by CEDA users.

Data Quality:
See dataset associated documentation
File Format:
These 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

TROPOspheric Monitoring Instrument (TROPOMI) Deployed on: Sentinel 5 Precursor

Computation Element: 1

Title Level 2 Methane (CH4) total column processing algorithm applied to Sentinel 5P TROPOspheric Monitoring Instrument (TROPOMI) raw data
Abstract This computation involves the Level 2 processing algorithm applied to raw TROPOspheric Monitoring Instrument (TROPOMI) data. The algorithm for retrieval of methane columns from the SENTINEL-5P instrument is based on earlier developments of a CO2 and CH4 retrieval algorithm from GOSAT, called RemoTeC [Butz et al., 2009; 2010; 2011; Schepers et al, 2012; Guerlet et al, 2013a]. In order to account for the effect of aerosols and cirrus, the algorithm retrieves the CH4 column simultaneously with the aerosol/cirrus amount (column integrated particle number concentration), a parameter related to the particle size distribution, and a parameter describing the height distribution. Here, the particle size distribution is described by a power-law function [Mishchenko et al, 1999] which only has two free parameters (related to amount and size). The choice of aerosol/cirrus parameters reflects the information content of the measurements as closely as possible. The retrieval algorithm uses the Level-1B reflectance measurements in the SWIR band and additionally in the NIR band between 757-774 nm (O2 A-band). Additional fit parameters are the surface albedo and its first-order spectral dependence in the two bands, and the total columns of carbon-monoxide and water vapor, respectively. In order to obtain a proper characterisation of the retrieved CH4 column, it is important to first retrieve a vertical profile (layer averaged number density in different layers of the model atmosphere) and use this retrieved vertical profile to calculate the vertical column. It has been chosen to provide the vertical column as a product, and not the full profile because the Degrees of Freedom for Signal (DFS) of the retrieved CH4 profile is approximately 1. The inversion is performed using Phillips-Tikhonov regularization in combination with a reduced step size Gauss-Newton iteration scheme. The forward model of the retrieval algorithm uses online radiative transfer calculations, fully including multiple scattering. Here, the radiative transfer model developed by Landgraf et al. [2001], and Hasekamp and Landgraf [2002; 2005] is being used. This model uses the Gauss-Seidel iterative method to solve the radiative transfer equation in a plane-parallel, vertically inhomogeneous atmosphere. To avoid time-consuming line-by-line calculations, the linear-k method developed by Hasekamp and Butz [2008] is employed. Absorption cross-sections of the relevant atmospheric trace gases are tabulated in a look-up table as functions of pressure and temperature. The optical properties of aerosols are also calculated from look-up tables as described in Dubovik et al. [2006]. Cloud Filtering As for the CO vertical column retrieval, a pre-processing step is performed to discard ground pixels contaminated by clouds. For CH4, only cloud-free ground pixels will be kept. The baseline approach for cloud/cirrus flagging is to use the cloud mask from the VIIRS instrument (on Suomi-NPP satellite, flying in close formation with SENTINEL-5P). With its 1 km x 1 km ground pixel size, the VIIRS cloud mask is much more flexible in defining the area that is required to be cloud-free than the cloud flagging from TROPOMI itself. However, in case VIIRS data are not available, the cloud mask will be obtained from TROPOMI measurements using either: - A comparison between the apparent surface pressure in the TROPOMI Cloud Level-2 product with the "true" surface pressure in ECMWF. - The "Two-band CH4 cloud filter" and the "Two-band H2O cloud filter".
Input Description None
Output Description None
Software Reference None
Output Description

None

  • units: Pa
  • var_id: apparent_scene_pressure
  • long_name: Apparent scene pressure from oxygen A-band depth
  • units: mol m-2
  • var_id: carbonmonoxide_total_column
  • standard_name: atmosphere_mole_content_of_carbon_monoxide
  • long_name: CO total vertical column
  • units: mol m-2
  • var_id: carbonmonoxide_total_column_precision
  • standard_name: atmosphere_mole_content_of_carbon_monoxide standard_error
  • long_name: CO total vertical column precision
  • units: 1
  • var_id: reflectance_cirrus_VIIRS_NIR
  • long_name: Cirrus reflectance from VIIRS for the NIR ground pixel
  • units: 1
  • var_id: reflectance_cirrus_VIIRS_SWIR
  • long_name: Cirrus reflectance from VIIRS for the SWIR ground pixel
  • units: 1
  • var_id: cloud_fraction_VIIRS_NIR_IFOV
  • long_name: Cloud fraction from VIIRS data in the NIR channel for the instantaneous field of view (band 6).
  • units: 1
  • var_id: cloud_fraction_VIIRS_SWIR_OFOVa
  • long_name: Cloud fraction from VIIRS data in the SWIR channel for the 10% upscaled field of view
  • units: 1
  • var_id: cloud_fraction_VIIRS_SWIR_OFOVc
  • long_name: Cloud fraction from VIIRS data in the SWIR channel for the 100% upscaled field of view
  • units: 1
  • var_id: cloud_fraction_VIIRS_SWIR_OFOVb
  • long_name: Cloud fraction from VIIRS data in the SWIR channel for the 50% upscaled field of view
  • units: 1
  • var_id: cloud_fraction_VIIRS_SWIR_IFOV
  • long_name: Cloud fraction from VIIRS data in the SWIR channel for the instantaneous field of view
  • units: 1
  • var_id: column_averaging_kernel
  • long_name: Column averaging kernel for the methane retrieval
  • units: m s-1
  • standard_name: eastward_wind
  • var_id: eastward_wind
  • long_name: Eastward wind from ECMWF at 10 meter height level
  • units: mol m-2
  • standard_name: atmosphere_mole_content_of_water_vapor
  • var_id: water_total_column
  • long_name: H2O total vertical column
  • units: mol m-2
  • var_id: water_total_column_precision
  • standard_name: atmosphere_mole_content_of_water_vapor standard_error
  • long_name: H2O total vertical column precision
  • units: 1
  • var_id: methane_mixing_ratio_histogram_axis
  • long_name: Histogram of the methane mixing ratio
  • var_id: instrument_configuration_identifier
  • long_name: IcID
  • var_id: instrument_configuration_version
  • long_name: IcVersion
  • var_id: surface_classification
  • long_name: Land-water mask and surface classification based on a static database
  • units: 1
  • var_id: maximum_reflectance_NIR
  • long_name: Maximum reflectance in the NIR channel
  • units: 1
  • var_id: maximum_reflectance_SWIR
  • long_name: Maximum reflectance in the SWIR channel
  • units: m s-1
  • standard_name: northward_wind
  • var_id: northward_wind
  • long_name: Northward wind from ECMWF at 10 meter height level
  • var_id: number_of_spectral_points_in_retrieval
  • long_name: Number of spectral points used in the retrieval
  • units: 1
  • var_id: methane_mixing_ratio_pdf_axis
  • long_name: Probability density function of methane dry air mixing ratio
  • long_name: Processing quality flags
  • var_id: processing_quality_flags
  • units: nm
  • var_id: wavelength_calibration_offset_NIR
  • long_name: Spectral shift in the NIR band, add value to L1B to obtain best fit result
  • units: nm
  • var_id: wavelength_calibration_offset_SWIR
  • long_name: Spectral shift in the SWIR band, add value to L1B to obtain best fit result
  • units: 1
  • var_id: methane_ratio_weak_strong_standard_deviation
  • long_name: Standard deviation of ratio of the methane column from weak and strong band over 9 ground pixels
  • units: 1
  • var_id: water_ratio_weak_strong_standard_deviation
  • long_name: Standard deviation of ratio of the water vapor column from weak and strong band over 9 ground pixels
  • units: Pa
  • var_id: apparent_scene_pressure_standard_deviation
  • long_name: Standard deviation of the apparent scene pressure from oxygen A-band depth over 9 ground pixels
  • units: m
  • standard_name: surface_altitude
  • var_id: surface_altitude
  • long_name: Surface altitude
  • var_id: time_utc
  • long_name: Time of observation as ISO 8601 date-time string
  • units: mol m-2
  • standard_name: atmosphere_mole_content_of_methane
  • var_id: methane_strong_twoband_total_column
  • long_name: Vertically integrated CH4 column from strong band
  • units: mol m-2
  • standard_name: atmosphere_mole_content_of_methane
  • var_id: methane_weak_twoband_total_column
  • long_name: Vertically integrated CH4 column from weak band
  • units: mol m-2
  • var_id: water_strong_twoband_total_column
  • standard_name: atmosphere_mole_content_of_water_vapor
  • long_name: Vertically integrated H2O column from strong band
  • units: mol m-2
  • standard_name: atmosphere_mole_content_of_water_vapor
  • var_id: water_weak_twoband_total_column
  • long_name: Vertically integrated H2O column from weak band
  • var_id: fluorescence_apriori
  • long_name: a priori fluorescence emission
  • units: mol s-1 m-2 nm-1 sr-1
  • units: 1
  • var_id: ground_pixel
  • long_name: across-track dimension index
  • units: 1
  • var_id: aerosol_optical_thickness_NIR
  • long_name: aerosol optical thickness in NIR band
  • units: 1
  • var_id: aerosol_optical_thickness_SWIR
  • long_name: aerosol optical thickness in SWIR channel
  • units: 1
  • var_id: aerosol_size
  • long_name: aerosol size parameter of the power law size distribution
  • units: m-2
  • var_id: aerosol_number_column
  • standard_name: atmosphere_number_content_of_aerosol_particles
  • long_name: aerosol total vertical number column
  • units: 1
  • var_id: scanline
  • long_name: along-track dimension index
  • units: 1e-9
  • standard_name: dry_atmosphere_mole_fraction_of_methane
  • var_id: methane_mixing_ratio_bias_corrected
  • long_name: bias corrected column-averaged dry-air mole fraction of methane
  • units: m
  • var_id: aerosol_mid_altitude
  • long_name: central altitude of aerosol altitude distribution. This is the geometric height above the geoid.
  • units: 1
  • var_id: chi_square_NIR
  • long_name: chi squared of fit in NIR band
  • units: 1
  • var_id: chi_square_SWIR
  • long_name: chi squared of fit in SWIR band
  • units: 1
  • var_id: chi_square
  • long_name: chi squared of fit in both SWIR and NIR band
  • units: 1e-9
  • standard_name: dry_atmosphere_mole_fraction_of_methane
  • var_id: methane_mixing_ratio
  • long_name: column averaged dry air mixing ratio of methane
  • units: 1e-9
  • standard_name: dry_atmosphere_mole_fraction_of_methane
  • var_id: methane_mixing_ratio_bias_corrected
  • long_name: corrected column-averaged dry-air mole fraction of methane
  • units: 1
  • var_id: qa_value
  • long_name: data quality value
  • units: 1
  • var_id: degrees_of_freedom_methane
  • long_name: degrees of freedom for \Methane profile
  • units: 1
  • var_id: degrees_of_freedom_aerosol
  • long_name: degrees of freedom for aerosol parameters
  • units: 1
  • var_id: degrees_of_freedom
  • long_name: degrees of freedom for signal
  • units: mol m-2
  • var_id: dry_air_subcolumns
  • long_name: dry air subcolumns
  • units: mol s-1 m-2 nm-1 sr-1
  • var_id: fluorescence
  • long_name: fluorescence emission
  • units: 1
  • var_id: satellite_orbit_phase
  • long_name: fractional satellite orbit phase
  • units: 1
  • long_name: geolocation flags
  • var_id: geolocation_flags
  • units: 1
  • long_name: ground pixel quality flag
  • var_id: geolocation_flags
  • units: m
  • standard_name: altitude
  • var_id: altitude_levels
  • long_name: height above the geoid
  • var_id: latitude_bounds
  • var_id: layer
  • var_id: level
  • var_id: longitude_bounds
  • var_id: methane_mixing_ratio_histogram
  • var_id: methane_mixing_ratio_histogram_bounds
  • var_id: methane_mixing_ratio_pdf
  • var_id: methane_mixing_ratio_pdf_bounds
  • units: mol m-2
  • var_id: methane_profile_apriori
  • standard_name: mole_content_of_methane_in_atmosphere_layer
  • long_name: mole content of methane in atmosphere layer
  • units: 1
  • var_id: number_of_iterations
  • long_name: number of iterations
  • var_id: number_of_spectral_points_in_retrieval_NIR
  • long_name: number of spectral points used in the retrieval.
  • units: milliseconds
  • var_id: delta_time
  • long_name: offset from reference start time of measurement
  • units: milliseconds
  • var_id: delta_time
  • long_name: offset of start time of measurement relative to time_reference
  • units: 1
  • var_id: corner
  • long_name: pixel corner index
  • units: m-2
  • var_id: aerosol_number_column_precision
  • standard_name: atmosphere_number_content_of_aerosol_particles standard_error
  • long_name: precision of aerosol total vertical column
  • units: m
  • var_id: aerosol_mid_altitude_precision
  • long_name: precision of central altitude of aerosol altitude distribution.
  • units: 1
  • var_id: aerosol_size_precision
  • long_name: precision of the aerosol size parameter of the power law size distribution
  • units: 1e-9
  • var_id: methane_mixing_ratio_precision
  • standard_name: dry_atmosphere_mole_fraction_of_methane standard_error
  • long_name: precision of the column averaged dry air mixing ratio of methane
  • units: 1
  • var_id: surface_albedo_NIR_precision
  • standard_name: surface_albedo standard_error
  • long_name: precision of the surface albedo in the NIR channel
  • units: 1
  • standard_name: surface_albedo standard_error
  • var_id: surface_albedo_SWIR_precision
  • long_name: precision of the surface albedo in the SWIR channel
  • units: Pa
  • var_id: pressure_interval
  • long_name: pressure difference between levels in the retrieval
  • units: m
  • var_id: satellite_altitude
  • long_name: satellite altitude
  • units: degrees_east
  • var_id: satellite_longitude
  • long_name: satellite_longitude
  • units: 1
  • var_id: scaled_small_pixel_variance
  • long_name: scaled small pixel variance
  • units: degree
  • standard_name: solar_azimuth_angle
  • long_name: solar azimuth angle
  • var_id: solar_azimuth_angle
  • units: degree
  • long_name: solar zenith angle
  • var_id: solar_zenith_angle
  • standard_name: solar_zenith_angle
  • units: degrees_north
  • var_id: satellite_latitude
  • long_name: sub satellite latitude
  • units: Pa
  • standard_name: surface_air_pressure
  • var_id: surface_pressure
  • long_name: surface air pressure
  • units: 1
  • standard_name: surface_albedo
  • var_id: surface_albedo_NIR
  • long_name: surface albedo in the NIR channel
  • units: 1
  • standard_name: surface_albedo
  • var_id: surface_albedo_SWIR
  • long_name: surface albedo in the SWIR channel
  • units: m
  • var_id: surface_altitude_precision
  • standard_name: surface_altitude standard_error
  • long_name: surface altitude precision
  • units: degree
  • standard_name: viewing_azimuth_angle
  • long_name: viewing azimuth angle
  • var_id: viewing_azimuth_angle
  • units: degree
  • long_name: viewing zenith angle
  • standard_name: viewing_zenith_angle
  • var_id: viewing_zenith_angle

Co-ordinate Variables

  • units: degrees_north
  • standard_name: latitude
  • var_id: latitude
  • long_name: pixel center latitude
  • units: degrees_east
  • standard_name: longitude
  • var_id: longitude
  • long_name: pixel center longitude
  • standard_name: time
  • var_id: time
  • units: seconds
  • long_name: reference time for the measurements
Coverage
Temporal Range
Start time:
2018-06-01T00:00:00
End time:
Ongoing
Geographic Extent

 
90.0000°
 
-180.0000°
 
180.0000°
 
-90.0000°