Dataset
Sentinel 5P: Formaldehyde (HCHO) Total Column level 2 data
Latest Data Update: 2023-04-19
Status: Ongoing
Online Status: ONLINE
Publication State: Published
Publication Date: 2022-11-14
Download Stats: last 12 months
Dataset Size: 49.92K Files | 16TB
Abstract
This dataset contains total column Formaldehyde (HCHO) data from the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Sentinel 5P satellite.
Sentinel 5 Precursor (S5P) was launched on the 13th of October 2017 carrying the TROPOspheric Monitoring Instrument (TROPOMI). The TROPOMI is a nadir-viewing, imaging spectrometer covering wavelength bands between the ultraviolet and the shortwave infrared. The instrument uses passive remote sensing techniques to attain its objective by measuring, at the Top Of Atmosphere (TOA), the solar radiation reflected by and radiated from the earth. In addition to the main product results, such as HCHO slant column, vertical column, and air mass factor, the level 2 (geolocated total columns) data files contain several additional parameters and diagnostic information.
Formaldehyde is an intermediate gas in almost all oxidation chains of Non-Methane Volatile Organic Compounds (NMVOC), leading eventually to CO2. NMVOCs are, together with NOx, CO, and CH4, among the most important precursors of tropospheric O3. The major HCHO source in the remote atmosphere is CH4 oxidation. Over the continents, the oxidation of higher NMVOCs emitted from vegetation, fires, traffic and industrial sources results in important and localised enhancements of the HCHO levels.
Citable as: Copernicus; European Space Agency (2022): Sentinel 5P: Formaldehyde (HCHO) Total Column level 2 data. NERC EDS Centre for Environmental Data Analysis, date of citation. https://catalogue.ceda.ac.uk/uuid/300559d22d9549049017f06bf38db929
Abbreviation: Not defined
Keywords: Sentinel 5P, Formaldehyde, HCHO, ESA
Details
| Previous Info: |
No news update for this record
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| Previously used record identifiers: |
No related previous identifiers.
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| Access rules: |
Public data: access to these data is available to both registered and non-registered users.
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
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| File Format: |
These data are in NetCDF format.
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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 Formaldehyde (HCHO) total column processing algorithm applied to Sentinel 5P TROPOspheric Monitoring Instrument (TROPOMI) raw data |
| Abstract | The general method used for the derivation of HCHO VCDs from UV spectral measurements is the Differential Optical Absorption Spectroscopy method (DOAS; Platt and Stutz, 2008) which involves two main steps. First, the effective slant column amount (corresponding to the integrated HCHO concentration along the mean atmospheric optical path: Ns) is derived through a least-squares fit of the measured Earth reflectance spectrum by laboratory absorption cross-sections and a low order polynomial. Subsequently, a correction is applied to the slant column values to correct for appearing biases that may be of known or unknown origin. Finally, slant columns are converted into vertical columns by means of air mass factors (AMF) obtained from suitable radiative transfer calculations, accounting for the presence of clouds, surface properties, and best-guess HCHO vertical profiles. In the UV, the sensitivity to HCHO concentrations in the boundary layer is intrinsically limited from space due to the combined effect of Rayleigh and Mie scattering that limits the radiation fraction scattered back toward the satellite. In addition, ozone absorption reduces the number of photons that reaches the lowest atmospheric layers. Furthermore, the absorption signatures of HCHO are weaker than those of other UV Vis absorbers, such as e.g. NO2. As a result, the retrieval of formaldehyde from space is noise sensitive and error prone. While the precision (or random error uncertainty) is driven by the signal to noise ratio of the recorded spectra and by the width of the retrieval interval, the trueness (or systematic error uncertainty) is limited by the current knowledge of the external parameters needed in the different retrieval steps. The selection of the optimal retrieval interval must maximize the sensitivity of the inversion to the HCHO absorption signatures while minimizing errors from geophysical and instrument related spectral features. The retrieval interval should be chosen as wide as possible to maximize the number of sampling points while avoiding overlap with strong atmospheric spectral features from interfering species (mainly O3, BrO, and O4). The DOAS algorithm intrinsically assumes that the atmosphere is optically thin so that the optical light path is independent of wavelength within the fitting window. Hence the method is accurate only for modest ozone absorption (i.e., for small to medium solar zenith angles). Generally, the effect of ozone misfit on the retrieval can be handled by introducing wavelength dependent-AMF in the fit, and by applying appropriate background corrections on the columns. The correlation with BrO absorption can be reduced by using two different wavelength intervals to fit BrO and HCHO (see section 5.3: Formaldehyde slant column retrieval). The Sentinel-5P sensor TROPOMI samples the Earth’s surface with a revisit time of one day and with an unprecedented spatial resolution of 7x3.5 km2 (5.5x3.5 km2 from 6 August 2019). Furthermore, the signal to noise ratio of TROPOMI is required to be equivalent to OMI in the UV-Visible range. This allows the resolution of fine details and S5P will arguably be a valuable tool to better study NMVOC emissions. Nevertheless, it poses additional constraints on the retrieval code for several reasons: 1. Computational speed: the Level 1b data flow delivers spectral measurements for band 3 with a size of 4 gigabytes per orbit (15 orbits daily). 2. Precision: given the required signal to noise ratio of measured spectra, the air quality requirements for HCHO [RD04] will not be met for individual ground pixels. Spatial and temporal averages of the HCHO columns will have to be considered in order to provide useful constraints on human and natural NMVOC emissions. 3. Trueness: currently, the spatial resolution of global-scale external parameters needed in the AMF calculation (e.g. albedo or a priori HCHO profiles) is much coarser than the resolution of TROPOMI. This introduces errors in the final vertical columns, mostly for coastal regions and localized sources (Heckel et al., 2011) To fully exploit the potential of satellite data, applications relying on tropospheric HCHO observations require high quality long-term time series, provided with well characterized errors and averaging kernels, and consistently retrieved from the different sensors. Furthermore, as the HCHO observations are aimed to be used synergistically with other species observations (e.g. for air quality applications), it is essential to homogenize as far as possible the retrieval methods as well as the external databases, in order to minimize systematic biases between the observations. |
| Input Description | None |
| Output Description | None |
| Software Reference | None |
| Output Description | None |
- units: 1
- var_id: aerosol_index_340_380
- standard_name: ultraviolet_aerosol_index
- long_name: Aerosol index from 380 and 340 nm
- units: 1
- var_id: doas_polynomial_coefficients
- long_name: DOAS polynomial coefficients
- units: m s-1
- standard_name: eastward_wind
- var_id: eastward_wind
- long_name: Eastward wind from ECMWF at 10 meter height level
- var_id: instrument_configuration_identifier
- long_name: IcID
- var_id: instrument_configuration_version
- long_name: IcVersion
- units: m s-1
- standard_name: northward_wind
- var_id: northward_wind
- long_name: Northward wind from ECMWF at 10 meter height level
- units: 1
- var_id: number_of_spectral_points_in_retrieval
- long_name: Number of spectral points used in the DOAS retrieval
- units: 1
- var_id: number_of_spectral_points_in_retrieval
- long_name: Number of spectral points used in the retrieval
- units: 1
- var_id: number_of_spectral_points_in_retrieval_win1
- long_name: Number of spectral points used in the retrieval in the first interval of the DOAS fit
- units: 1
- long_name: Processing quality flags
- var_id: processing_quality_flags
- units: mol m-2
- var_id: formaldehyde_tropospheric_vertical_column_trueness
- long_name: Systematic error of vertical column density
- var_id: time_utc
- long_name: Time of observation as ISO 8601 date-time string
- units: 1
- var_id: ground_pixel
- long_name: across-track dimension index
- units: 1
- var_id: scanline
- long_name: along-track dimension index
- units: 1
- var_id: amf_scd0_error_median
- units: 1
- var_id: amf_scd0_median
- units: mol m-2
- standard_name: TBA
- var_id: formaldehyde_tropospheric_vertical_column_correction
- long_name: background correction value which is added to the vertical column density
- units: 1
- var_id: calibration_subwindows_root_mean_square
- standard_name: TBA
- long_name: calibration rms per subwindow
- units: nm
- standard_name: TBA
- var_id: calibration_subwindows_wavelength
- long_name: calibration wavelength center in each subwindow
- units: 1
- var_id: formaldehyde_clear_air_mass_factor
- long_name: clear air mass factor
- units: molec cm-2
- var_id: clear_amf_scd0
- units: 1
- standard_name: cloud_albedo
- long_name: cloud albedo from the CRB model
- var_id: cloud_albedo_crb
- units: 1
- standard_name: cloud_albedo_standard_error
- long_name: cloud albedo precision from the CRB model
- var_id: cloud_albedo_crb_precision
- units: 1
- var_id: cloud_fraction_intensity_weighted
- long_name: cloud fraction intensity weighted
- units: m
- standard_name: TBD
- long_name: cloud radiometric optical centroid height from the CRB model
- var_id: cloud_height_crb
- units: m
- standard_name: TBD
- long_name: cloud radiometric optical centroid height precision from the CRB model
- var_id: cloud_height_crb_precision
- units: Pa
- standard_name: TBD
- var_id: cloud_pressure_crb
- long_name: cloud radiometric optical centroid pressure from the CRB model
- units: Pa
- standard_name: TBD
- var_id: cloud_pressure_crb_precision
- long_name: cloud radiometric optical centroid pressure precision from the CRB model
- units: 1
- var_id: formaldehyde_cloudy_air_mass_factor
- long_name: cloudy air mass factor
- units: 1
- standard_name: TBA
- var_id: calibration_polynomial_coefficients
- long_name: computed coefficients of the polynomial function
- units: mol m-2
- standard_name: TBA
- var_id: formaldehyde_slant_column_corrected
- long_name: corrected slant column density
- units: 1
- var_id: qa_value
- long_name: data quality value
- units: 1
- var_id: degrees_of_polynomial_shift
- long_name: degrees_of_polynomial_shift dimension index
- units: 1
- var_id: detector_rows
- long_name: detector_rows dimension index
- var_id: earthshine_reference_radiance
- units: mol.m-2.nm-1.sr-1.s-1
- units: nm
- var_id: earthshine_reference_wavelength
- units: 1
- standard_name: TBD
- long_name: effective radiometric cloud fraction from the CRB model
- var_id: cloud_fraction_crb
- units: 1
- standard_name: TBD
- long_name: effective radiometric cloud fraction precision from the CRB model
- var_id: cloud_fraction_crb_precision
- var_id: formaldehyde_total_column_histogram
- var_id: formaldehyde_total_column_pdf
- 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: 1
- var_id: histogram_axis
- units: nm
- standard_name: TBA
- var_id: calibration_subwindows_shift
- long_name: irradiance wavelengths shift fitted values per subwindow
- units: 1
- standard_name: TBA
- var_id: calibration_subwindows_squeeze
- long_name: irradiance wavelengths squeeze fitted values per subwindow
- units: 1
- var_id: surface_classification
- long_name: land-water mask
- units: degrees_north
- var_id: latitude_bounds
- units: 1
- var_id: latitude_grids
- long_name: latitude_grids dimension index
- units: 1
- var_id: layer
- long_name: layer dimension index
- units: degrees_east
- var_id: longitude_bounds
- units: 1
- var_id: number_of_iterations_in_retrieval
- long_name: number of iterations used in the retrieval
- units: 1
- var_id: number_of_iterations_in_retrieval_win1
- long_name: number of iterations used in the retrieval in the first interval of the doas fit
- units: 1
- var_id: number_of_spectral_points_in_retrieval_win1
- long_name: number of spectral points used in the retrieval in the first interval of the doas fit
- units: 1
- var_id: number_of_calibrations
- long_name: number_of_calibrations dimension index
- units: 1
- var_id: number_of_doas_polynomial_coefficients
- long_name: number_of_doas_polynomial_coefficients dimension index
- units: 1
- var_id: number_of_slant_columns
- long_name: number_of_slant_columns dimension index
- units: 1
- var_id: number_of_slant_columns_first_win1
- long_name: number_of_slant_columns_first_win1 dimension index
- units: 1
- var_id: number_of_subwindows
- long_name: number_of_subwindows dimension index
- units: milliseconds
- var_id: delta_time
- long_name: offset from reference start time of measurement
- units: mol m-2
- var_id: offsets
- units: mol m-2
- var_id: offsets_scd0
- units: 1
- var_id: pdf_axis
- units: 1
- var_id: corner
- long_name: pixel corner index
- units: 1
- var_id: polynomial_coefficients
- units: 1
- var_id: polynomial_coefficients_scd0
- units: nm
- var_id: fitted_radiance_shift
- long_name: radiance wavelength shift from the doas fit
- units: 1
- var_id: fitted_radiance_squeeze
- long_name: radiance wavelength squeeze/stretch from the doas fit
- units: 1
- var_id: cloud_fraction_intensity_weighted_precision
- long_name: random error of the cloud fraction intensity weighted
- units: 1
- var_id: formaldehyde_tropospheric_air_mass_factor_precision
- long_name: random error of the tropospheric air mass factor
- units: mol m-2
- var_id: formaldehyde_tropospheric_vertical_column_precision
- standard_name: troposphere_mole_content_of formaldehyde standard_error
- long_name: random error of vertical column density
- units: 1
- var_id: fitted_root_mean_square
- long_name: root mean square from the doas fit
- units: 1
- var_id: fitted_root_mean_square_win1
- long_name: root mean square in the first interval of the doas fit
- 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: 1
- var_id: sea_ice_cover
- long_name: sea-ice-cover
- units: 1
- standard_name: TBA
- var_id: formaldehyde_slant_column_correction_flag
- long_name: slant column density background correction flag
- units: mol m-2
- var_id: fitted_slant_columns_precision
- long_name: slant columns errors of all absorbers
- units: mol m-2
- var_id: fitted_slant_columns_win1_precision
- long_name: slant columns errors of all absorbers in the first interval of the doas fit
- units: mol m-2
- var_id: fitted_slant_columns
- long_name: slant columns of all absorbers
- units: mol m-2
- var_id: fitted_slant_columns_win1
- long_name: slant columns of all absorbers in the first interval of the doas fit
- units: 1
- var_id: snow_cover
- long_name: snow-cover
- units: 1
- long_name: snow-ice mask
- var_id: snow_ice_flag_nise
- 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: 1
- var_id: surface_albedo
- standard_name: TBA
- long_name: surface albdeo
- units: 1
- standard_name: TBA
- var_id: surface_albedo_ge_ler
- long_name: surface albdeo ge-ler
- units: 1
- standard_name: TBA
- var_id: surface_albedo_selected
- long_name: surface albdeo selected
- units: m
- standard_name: surface_altitude
- var_id: surface_altitude
- long_name: surface altitude
- units: m
- var_id: surface_altitude_precision
- standard_name: surface_altitude standard_error
- long_name: surface altitude precision
- units: Pa
- standard_name: surface_air_pressure
- long_name: surface_air_pressure
- var_id: surface_pressure
- units: K
- var_id: surface_temperature
- standard_name: surface_air_temperature
- long_name: surface_air_temperature
- units: mol m-2
- var_id: formaldehyde_tropospheric_vertical_column_kernel_trueness
- long_name: systematic error of the air mass factor for the kernel tropospheric formaldehyde
- units: mol m-2
- standard_name: TBA
- var_id: formaldehyde_slant_column_corrected_trueness
- long_name: systematic error of the slant column density
- units: 1
- var_id: formaldehyde_tropospheric_air_mass_factor_trueness
- long_name: systematic error of the tropospheric air mass factor
- units: Pa
- var_id: tm5_constant_a
- units: 1
- var_id: tm5_constant_b
- units: 1
- var_id: formaldehyde_profile_apriori
- long_name: tm5_hcho a priori profile (vmr) interpolated in space and time on ground pixel
- units: 1
- var_id: tm5_tropopause_layer_index
- units: 1
- var_id: averaging_kernel
- long_name: total column averaging kernel
- units: 1
- var_id: formaldehyde_tropospheric_air_mass_factor
- long_name: tropospheric air mass factor
- var_id: vcd_scd0_error_median
- units: molec cm-2
- units: molec cm-2
- var_id: vcd_scd0_median
- units: mol m-2
- var_id: formaldehyde_tropospheric_vertical_column
- standard_name: troposphere_mole_content_of_formaldehyde
- long_name: vertical column of formaldehyde
- units: 1
- var_id: vertices
- long_name: vertices dimension index
- 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
- units: 1
- var_id: wavelengths
- long_name: wavelengths dimension index
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:
2018-05-14T00:00:00
End time:
Ongoing
Geographic Extent
90.0000° |
||
-180.0000° |
180.0000° |
|
-90.0000° |
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