# S5P_L2_NO2

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `S5P_L2_NO2` 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_bounds | double | {time, vertical, 2} | [Pa] | pressure boundaries
tropospheric_NO2_column_number_density | float | {time} | [mol/m^2] | tropospheric vertical column of NO2
tropospheric_NO2_column_number_density_uncertainty | float | {time} | [mol/m^2] | uncertainty of the tropospheric vertical column of NO2 (standard error)
tropospheric_NO2_column_number_density_validity | int8 | {time} |  | continuous quality descriptor, varying between 0 (no data) and 100 (full quality data)
tropospheric_NO2_column_number_density_amf | float | {time} | [] | tropospheric air mass factor, computed by integrating the altitude dependent air mass factor over the atmospheric layers from the surface up to and including the layer with the tropopause
tropospheric_NO2_column_number_density_avk | float | {time, vertical} | [] | averaging kernel for the tropospheric vertical column number density of NO2
NO2_column_number_density | float | {time} | [mol/m^2] | total vertical column of NO2
NO2_column_number_density_uncertainty | float | {time} | [mol/m^2] | uncertainty of the total vertical column of NO2 (standard error)
NO2_column_number_density_amf | float | {time} | [] | total air mass factor, computed by integrating the altitude dependent air mass factor over the atmospheric layers from the surface to top-of-atmosphere
NO2_column_number_density_avk | float | {time, vertical} | [] | averaging kernel for the air mass factor correction, describing the NO2 profile sensitivity of the vertical column density
stratospheric_NO2_column_number_density | float | {time} | [mol/m^2] | stratospheric vertical column of NO2
stratospheric_NO2_column_number_density_uncertainty | float | {time} | [mol/m^2] | uncertainty of the stratospheric vertical column of NO2 (standard error)
stratospheric_NO2_column_number_density_amf | float | {time} | [] | stratospheric air mass factor
stratospheric_NO2_column_number_density_avk | float | {time, vertical} | [] | averaging kernel for the stratospheric vertical column number density of NO2
NO2_slant_column_number_density | float | {time} | [mol/m^2] | slant column of NO2
NO2_slant_column_number_density_uncertainty | float | {time} | [mol/m^2] | uncertainty of the slant column of NO2
cloud_fraction | float | {time} | [] | cloud fraction for NO2 fitting window
absorbing_aerosol_index | float | {time} | [] | aerosol index
cloud_albedo | float | {time} | [] | cloud albedo
cloud_pressure | float | {time} | [Pa] | cloud pressure
scene_albedo | float | {time} | [] | scene albedo
scene_pressure | float | {time} | [Pa] | apparent scene 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
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)
tropopause_pressure | double | {time} | [Pa] | tropopause pressure
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_NO2` products.

option name | legal values | description
--- | --- | ---
data | o22cld | whether to ingest the NO2 data (default) or the O2-O2 cloud data (data=o22cld)
total_column | summed, total | whether to use nitrogendioxide_total_column (which is derived from the total slant column diveded by the total amf) or nitrogendioxide_summed_total_column (which is the sum of the retrieved tropospheric and stratospheric columns); option values are ‘summed’ (default) and ‘total’
cloud_fraction | radiance | whether to ingest the cloud fraction (default) or the radiance cloud fraction (cloud_fraction=radiance) for the NO2 data

This definition is only applicable when: data unset

## 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); the time associated with a scanline is repeated for each pixel in the scanline
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_bounds | path | /PRODUCT/tm5_constant_a[], /PRODUCT/tm5_constant_b[], /PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_pressure[]
description | pressure in Pa at level k is derived from surface pressure in Pa as: tm5_constant_a[k] + tm5_constant_b[k] * surface_pressure[]; the top of atmosphere pressure is clamped to 1e-3 Pa
tropospheric_NO2_column_number_density | path | /PRODUCT/nitrogendioxide_tropospheric_column[]
tropospheric_NO2_column_number_density_uncertainty | path | /PRODUCT/nitrogendioxide_tropospheric_column_precision[]
tropospheric_NO2_column_number_density_validity | path | /PRODUCT/qa_value
tropospheric_NO2_column_number_density_amf | path | /PRODUCT/air_mass_factor_troposphere[]
tropospheric_NO2_column_number_density_avk | path | /PRODUCT/averaging_kernel[], /PRODUCT/air_mass_factor_total[], /PRODUCT/air_mass_factor_troposphere[], /PRODUCT/tm5_tropopause_layer_index[]
description | averaging_kernel[layer] = if layer <= tm5_tropopause_layer_index then averaging_kernel[layer] * air_mass_factor_total / air_mass_factor_troposphere else 0
NO2_column_number_density | condition | total_column=summed or total_column unset
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/nitrogendioxide_summed_total_column[]
condition | total_column=total
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/nitrogendioxide_total_column[]
NO2_column_number_density_uncertainty | condition | total_column=summed or total_column unset
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/nitrogendioxide_summed_total_column_precision[]
condition | total_column=total
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/nitrogendioxide_total_column_precision[]
NO2_column_number_density_amf | path | /PRODUCT/air_mass_factor_total[]
NO2_column_number_density_avk | path | /PRODUCT/averaging_kernel[]
stratospheric_NO2_column_number_density | path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/nitrogendioxide_stratospheric_column[]
stratospheric_NO2_column_number_density_uncertainty | path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/nitrogendioxide_stratospheric_column_precision[]
stratospheric_NO2_column_number_density_amf | path | /PRODUCT/air_mass_factor_troposphere[]
stratospheric_NO2_column_number_density_avk | path | /PRODUCT/averaging_kernel[], /PRODUCT/air_mass_factor_total[], /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/air_mass_factor_stratosphere[], /PRODUCT/tm5_tropopause_layer_index[]
description | averaging_kernel[layer] = if layer > tm5_tropopause_layer_index then averaging_kernel[layer] * air_mass_factor_total / air_mass_factor_stratosphere else 0
NO2_slant_column_number_density | path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/nitrogendioxide_slant_column_density[]
NO2_slant_column_number_density_uncertainty | path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/nitrogendioxide_slant_column_density_precision[]
cloud_fraction | condition | cloud_fraction unset
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/cloud_fraction_crb_nitrogendioxide_window[]
condition | cloud_fraction=radiance
path | /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/cloud_radiance_fraction_nitrogendioxide_window[]
absorbing_aerosol_index | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/aerosol_index_354_388
cloud_albedo | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_albedo_crb
cloud_pressure | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_pressure_crb
scene_albedo | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/scene_albedo
scene_pressure | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/apparent_scene_pressure
surface_albedo | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_albedo_nitrogendioxide_window
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 >= 01.03.00
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/northward_wind[]
surface_zonal_wind_velocity | available | optional
condition | processor version >= 01.03.00
path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/eastward_wind[]
snow_ice_type | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/snow_ice_flag[]
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 | path | /PRODUCT/SUPPORT_DATA/INPUT_DATA/snow_ice_flag[]
description | if 1 <= snow_ice_flag <= 100 then snow_ice_flag/100.0 else 0.0
tropopause_pressure | path | /PRODUCT/tm5_constant_a[], /PRODUCT/tm5_constant_b[], /PRODUCT/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: tm5_constant_a[k + 1] + tm5_constant_b[k + 1] * surface_pressure[]