# S5P_L2_HCHO

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `S5P_L2_HCHO` data.

field name | type | dimensions | unit | description
--- | --- | --- | --- | ---
scan_subindex | int16 | {time} |  | pixel index (0-based) within the scanline
datetime_start | double | {time} | [seconds since 2010-01-01] | start time of the measurement
datetime_length | double |  | [s] | duration of the measurement
orbit_index | int32 |  |  | absolute orbit number
validity | int32 | {time} |  | processing quality flag
latitude | float | {time} | [degree_north] | latitude of the ground pixel center (WGS84)
longitude | float | {time} | [degree_east] | longitude of the ground pixel center (WGS84)
latitude_bounds | float | {time, 4} | [degree_north] | latitudes of the ground pixel corners (WGS84)
longitude_bounds | float | {time, 4} | [degree_east] | longitudes of the ground pixel corners (WGS84)
sensor_latitude | float | {time} | [degree_north] | latitude of the geodetic sub-satellite point (WGS84)
sensor_longitude | float | {time} | [degree_east] | longitude of the goedetic sub-satellite point (WGS84)
sensor_altitude | float | {time} | [m] | altitude of the satellite with respect to the geodetic sub-satellite point (WGS84)
solar_zenith_angle | float | {time} | [degree] | zenith angle of the Sun at the ground pixel location (WGS84); angle measured away from the vertical
solar_azimuth_angle | float | {time} | [degree] | azimuth angle of the Sun at the ground pixel location (WGS84); angle measured East-of-North
sensor_zenith_angle | float | {time} | [degree] | zenith angle of the satellite at the ground pixel location (WGS84); angle measured away from the vertical
sensor_azimuth_angle | float | {time} | [degree] | azimuth angle of the satellite at the ground pixel location (WGS84); angle measured East-of-North
pressure | double | {time, vertical} | [Pa] | pressure
tropospheric_HCHO_column_number_density | float | {time} | [mol/m^2] | tropospheric HCHO column number density
tropospheric_HCHO_column_number_density_uncertainty_random | float | {time} | [mol/m^2] | uncertainty of the tropospheric HCHO column number density due to random effects
tropospheric_HCHO_column_number_density_uncertainty_systematic | float | {time} | [mol/m^2] | uncertainty of the tropospheric HCHO column number density due to systematic effects
tropospheric_HCHO_column_number_density_validity | int8 | {time} |  | continuous quality descriptor, varying between 0 (no data) and 100 (full quality data)
tropospheric_HCHO_column_number_density_avk | float | {time, vertical} | [] | averaging kernel for the tropospheric HCHO column number density
HCHO_volume_mixing_ratio_dry_air_apriori | float | {time, vertical} | [ppv] | HCHO apriori profile in volume mixing ratios (with regard to dry air)
tropospheric_HCHO_column_number_density_amf | float | {time} | [] | tropospheric air mass factor
tropospheric_HCHO_column_number_density_amf_uncertainty_random | float | {time} | [] | random part of the tropospheric air mass factor uncertainty
tropospheric_HCHO_column_number_density_amf_uncertainty_systematic | float | {time} | [] | systematic part of the tropospheric air mass factor uncertainty
HCHO_slant_column_number_density | float | {time} | [mol/m^2] | HCHO slant column number density
HCHO_slant_column_number_density_uncertainty | float | {time} | [mol/m^2] | uncertainty of the HCHO slant column number density
absorbing_aerosol_index | float | {time} | [] | aerosol index
cloud_albedo | float | {time} | [] | cloud albedo
cloud_albedo_uncertainty | float | {time} | [] | uncertainty of the cloud albedo
cloud_fraction | float | {time} | [] | cloud fraction
cloud_fraction_uncertainty | float | {time} | [] | uncertainty of the cloud fraction
cloud_height | float | {time} | [km] | cloud height
cloud_height_uncertainty | float | {time} | [km] | uncertainty of the cloud height
cloud_pressure | float | {time} | [Pa] | cloud pressure
cloud_pressure_uncertainty | float | {time} | [Pa] | uncertainty of the cloud pressure
surface_albedo | float | {time} | [] | surface albedo
surface_altitude | float | {time} | [m] | surface altitude
surface_altitude_uncertainty | float | {time} | [m] | surface altitude precision
surface_pressure | float | {time} | [Pa] | surface pressure
surface_meridional_wind_velocity | float | {time} | [m/s] | northward wind
surface_zonal_wind_velocity | float | {time} | [m/s] | eastward wind
scene_albedo | float | {time} | [] | effective scene albedo
scene_pressure | float | {time} | [Pa] | scene pressure
tropopause_pressure | double | {time} | [Pa] | tropopause pressure
snow_ice_type | int8 | {time} |  | surface snow/ice type; enumeration values: snow_free_land (0), sea_ice (1), permanent_ice (2), snow (3), ocean (4)
sea_ice_fraction | float | {time} | [] | sea-ice concentration (as a fraction)
index | int32 | {time} |  | zero-based index of the sample within the source product

## Ingestion options

The table below lists the available ingestion options for `S5P_L2_HCHO` products.

option name | legal values | description
--- | --- | ---
amf | clear_sky | whether to ingest the default amf, vertical column and avk (default) or the clear sky amf, scaled vertical column, and omit the avk (amf=clear_sky)
cloud_fraction | radiance | whether to ingest the cloud fraction (default) or the radiance cloud fraction (cloud_fraction=radiance)

## Mapping description

The table below details where and how each variable was retrieved from the input product.

field name | mapping description
--- | ---
scan_subindex | description | the scanline and pixel dimensions are collapsed into a temporal dimension; the index of the pixel within the scanline is computed as the index on the temporal dimension modulo the number of scanlines
datetime_start | path | /PRODUCT/time, /PRODUCT/delta_time[]
description | time converted from milliseconds since a reference time (given as seconds since 2010-01-01) to seconds since 2010-01-01 (using 86400 seconds per day)
datetime_length | path | /@time_coverage_resolution
description | the measurement length is parsed assuming the ISO 8601 ‘PT%(interval_seconds)fS’ format
orbit_index | path | /@orbit
validity | path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/processing_quality_flags[]
description | the uint32 data is cast to int32
latitude | path | /PRODUCT/latitude[]
longitude | path | /PRODUCT/longitude[]
latitude_bounds | path | /PRODUCT/SUPPORT_DATA/GEOLOCATIONS/latitude_bounds[]
longitude_bounds | path | /PRODUCT/SUPPORT_DATA/GEOLOCATIONS/longitude_bounds[]
sensor_latitude | path | /PRODUCT/SUPPORT_DATA/GEOLOCATIONS/satellite_latitude[]
description | the satellite latitude associated with a scanline is repeated for each pixel in the scanline
sensor_longitude | path | /PRODUCT/SUPPORT_DATA/GEOLOCATIONS/satellite_longitude[]
description | the satellite longitude associated with a scanline is repeated for each pixel in the scanline
sensor_altitude | path | /PRODUCT/SUPPORT_DATA/GEOLOCATIONS/satellite_altitude[]
description | the satellite altitude associated with a scanline is repeated for each pixel in the scanline
solar_zenith_angle | path | /PRODUCT/SUPPORT_DATA/GEOLOCATIONS/solar_zenith_angle[]
solar_azimuth_angle | path | /PRODUCT/SUPPORT_DATA/GEOLOCATIONS/solar_azimuth_angle[]
sensor_zenith_angle | path | /PRODUCT/SUPPORT_DATA/GEOLOCATIONS/viewing_zenith_angle[]
sensor_azimuth_angle | path | /PRODUCT/SUPPORT_DATA/GEOLOCATIONS/viewing_azimuth_angle[]
pressure | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/tm5_constant_a[], /PRODUCT/SUPPORT_DATA/INPUT_DATA/tm5_constant_b[], /PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_pressure[]
description | pressure in Pa at layer k is derived from surface pressure in Pa as: tm5_constant_a[k] + tm5_constant_b[k] * surface_pressure[]
tropospheric_HCHO_column_number_density | condition | amf unset
path | /PRODUCT/formaldehyde_tropospheric_vertical_column[]
condition | amf=clear_sky
path | /PRODUCT/formaldehyde_tropospheric_vertical_column[], /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_tropospheric_air_mass_factor[], /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_clear_air_mass_factor[]
description | vertical_column = formaldehyde_tropospheric_vertical_column * formaldehyde_tropospheric_air_mass_factor / formaldehyde_clear_air_mass_factor
tropospheric_HCHO_column_number_density_uncertainty_random | condition | amf unset
path | /PRODUCT/formaldehyde_tropospheric_vertical_column_precision[]
condition | amf=clear_sky
path | /PRODUCT/formaldehyde_tropospheric_vertical_column_precision[], /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_tropospheric_air_mass_factor[], /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_clear_air_mass_factor[]
description | uncertainty_random = formaldehyde_tropospheric_vertical_column_precision * formaldehyde_tropospheric_air_mass_factor / formaldehyde_clear_air_mass_factor
tropospheric_HCHO_column_number_density_uncertainty_systematic | path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_tropospheric_vertical_column_trueness[]
tropospheric_HCHO_column_number_density_validity | path | /PRODUCT/qa_value
tropospheric_HCHO_column_number_density_avk | available | optional
condition | amf unset and processor version < 02.00.00
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/averaging_kernel[]
condition | amf unset and processor version >= 02.00.00
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/averaging_kernel[], /PRODUCT/SUPPORT_DATA/INPUT_DATA/tm5_tropopause_layer_index[]
description | averaging_kernel[layer] = if layer <= tm5_tropopause_layer_index then averaging_kernel[layer] else 0
HCHO_volume_mixing_ratio_dry_air_apriori | available | optional
condition | NRTI or processor version >= 01.00.00
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_profile_apriori[]
tropospheric_HCHO_column_number_density_amf | condition | amf unset
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_tropospheric_air_mass_factor[]
condition | amf=clear_sky
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_clear_air_mass_factor[]
tropospheric_HCHO_column_number_density_amf_uncertainty_random | available | optional
condition | processor version < 02.08.00
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_tropospheric_air_mass_factor_precision[]
tropospheric_HCHO_column_number_density_amf_uncertainty_systematic | path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_tropospheric_air_mass_factor_trueness[]
HCHO_slant_column_number_density | path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_slant_column_corrected[]
HCHO_slant_column_number_density_uncertainty | path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/formaldehyde_slant_column_corrected_trueness[]
absorbing_aerosol_index | available | optional
condition | OFFL
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/aerosol_index_340_380
cloud_albedo | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_albedo_crb
cloud_albedo_uncertainty | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_albedo_crb_precision
cloud_fraction | condition | cloud_fraction unset
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_fraction_crb[]
condition | cloud_fraction=radiance
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/cloud_fraction_intensity_weighted[]
cloud_fraction_uncertainty | condition | cloud_fraction unset
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_fraction_crb_precision[]
condition | cloud_fraction=radiance
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/cloud_fraction_intensity_weighted_precision[]
cloud_height | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_height_crb
cloud_height_uncertainty | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_height_crb_precision
cloud_pressure | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_pressure_crb
cloud_pressure_uncertainty | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_pressure_crb_precision
surface_albedo | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_albedo
surface_altitude | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_altitude[]
surface_altitude_uncertainty | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_altitude_precision[]
surface_pressure | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_pressure[]
surface_meridional_wind_velocity | available | optional
condition | processor version >= 02.00.00
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/northward_wind[]
surface_zonal_wind_velocity | available | optional
condition | processor version >= 02.00.00
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/eastward_wind[]
scene_albedo | available | optional
condition | OFFL and processor version >= 02.08.00
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/effective_albedo[]
scene_pressure | available | optional
condition | OFFL and processor version >= 02.08.00
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/scene_pressure[]
tropopause_pressure | available | optional
condition | processor version >= 02.00.00
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/tm5_constant_a[], /PRODUCT/SUPPORT_DATA/INPUT_DATA/tm5_constant_b[], /PRODUCT/SUPPORT_DATA/INPUT_DATA/tm5_tropopause_layer_index[], /PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_pressure[]
description | pressure in Pa at tropause is derived from the upper bound of the layer with tropopause layer index k: exp((log(tm5_constant_a[k] + tm5_constant_b[k] * surface_pressure[]) + log(tm5_constant_a[k + 1] + tm5_constant_b[k + 1] * surface_pressure[]))/2.0)
snow_ice_type | available | optional
condition | processor version >= 01.00.00
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/snow_ice_flag_nise[]
description | 0: snow_free_land (0), 1-100: sea_ice (1), 101: permanent_ice (2), 103: snow (3), 255: ocean (4), other values map to -1
sea_ice_fraction | available | optional
condition | processor version >= 01.00.00
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/snow_ice_flag_nise[]
description | if 1 <= snow_ice_flag <= 100 then snow_ice_flag/100.0 else 0.0