# S5P_L2_AER_AI

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `S5P_L2_AER_AI` 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
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
absorbing_aerosol_index | float | {time} | [] | aerosol index
absorbing_aerosol_index_uncertainty | float | {time} | [] | uncertainty of the aerosol index
absorbing_aerosol_index_validity | int8 | {time} |  | continuous quality descriptor, varying between 0 (no data) and 100 (full quality data)
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_AER_AI` products.

option name | legal values | description
--- | --- | ---
wavelength_ratio | 354_388nm, 340_380nm, 335_367nm | ingest aerosol index retrieved at wavelengths 354/388 nm (default), 340/380 nm, or 335/367 nm

## 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[]
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[]
absorbing_aerosol_index | condition | wavelength_ratio=354_388nm or wavelength_ratio unset
path | /PRODUCT/aerosol_index_354_388
condition | wavelength_ratio=340_380nm
path | /PRODUCT/aerosol_index_340_380
condition | wavelength_ratio=335_367nm and processor version >= 02.04.00
path | /PRODUCT/aerosol_index_335_367
absorbing_aerosol_index_uncertainty | condition | wavelength_ratio=354_388nm (default)
path | /PRODUCT/aerosol_index_354_388_precision
condition | wavelength_ratio=340_380nm
path | /PRODUCT/aerosol_index_340_380_precision
condition | wavelength_ratio=335_367nm
path | /PRODUCT/aerosol_index_335_367_precision
absorbing_aerosol_index_validity | path | /PRODUCT/qa_value
snow_ice_type | available | optional
condition | processor version >= 02.07.00
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 | available | optional
condition | processor version >= 02.07.00
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