# ECA_ATL_ALD_2A

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `ECA_ATL_ALD_2A` data.

field name | type | dimensions | unit | description
--- | --- | --- | --- | ---
datetime | double | {time} | [seconds since 2000-01-01] | UTC time
latitude | double | {time} | [degree_north] | Geodetic latitude
longitude | double | {time} | [degree_east] | Geodetic longitude
orbit_index | int32 |  |  | absolute orbit number
altitude_bounds | float | {time, vertical, 2} | [m] | aerosol layer base and top
aerosol_optical_depth | float | {time, vertical} | [] | aerosol layer optical thickness 355nm
aerosol_optical_depth_uncertainty | float | {time, vertical} | [] | aerosol layer optical thickness 355nm error
aerosol_extinction_coefficient | float | {time, vertical} | [1/m] | aerosol layer mean extinction 355nm
aerosol_extinction_coefficient_uncertainty | float | {time, vertical} | [1/m] | aerosol layer mean extinction 355nm error
aerosol_backscatter_coefficient | float | {time, vertical} | [1/m/sr] | aerosol layer mean backscatter 355nm
aerosol_backscatter_coefficient_uncertainty | float | {time, vertical} | [1/m/sr] | aerosol layer mean backscatter 355nm error
lidar_ratio | float | {time, vertical} | [sr] | aerosol layer mean lidar ratio 355nm
lidar_ratio_uncertainty | float | {time, vertical} | [sr] | aerosol layer mean lidar ratio 355nm error
linear_depolarization_ratio | float | {time, vertical} | [] | aerosol layer mean depolarization ratio 355nm
linear_depolarization_ratio_uncertainty | float | {time, vertical} | [] | aerosol layer mean depolarization ratio 355nm error
validity | int8 | {time} |  | quality status
wavelength | float |  | [nm] | lidar wavelength
index | int32 | {time} |  | zero-based index of the sample within the source product

## Mapping description

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

field name | mapping description
--- | ---
datetime | path | /ScienceData/time
latitude | path | /ScienceData/latitude
longitude | path | /ScienceData/longitude
orbit_index | path | /HeaderData/VariableProductHeader/MainProductHeader/orbitNumber
altitude_bounds | path | /ScienceData/aerosol_layer_base, /ScienceData/aerosol_layer_top, /ScienceData/geoid_offset
description | the vertical grid is inverted to make it ascending; altitude_bounds[i,j,0] = aerosol_layer_base[i,j] - geoid_offset[i]; altitude_bounds[i,j,1] = aerosol_layer_top[i,j] - geoid_offset[i]
aerosol_optical_depth | path | /ScienceData/aerosol_layer_optical_thickness_355nm
description | the vertical grid is inverted to make it ascending
aerosol_optical_depth_uncertainty | path | /ScienceData/aerosol_layer_optical_thickness_355nm_error
description | the vertical grid is inverted to make it ascending
aerosol_extinction_coefficient | path | /ScienceData/aerosol_layer_mean_extinction_355nm
description | the vertical grid is inverted to make it ascending
aerosol_extinction_coefficient_uncertainty | path | /ScienceData/aerosol_layer_mean_extinction_355nm_error
description | the vertical grid is inverted to make it ascending
aerosol_backscatter_coefficient | path | /ScienceData/aerosol_layer_mean_backscatter_355nm
description | the vertical grid is inverted to make it ascending
aerosol_backscatter_coefficient_uncertainty | path | /ScienceData/aerosol_layer_mean_backscatter_355nm_error
description | the vertical grid is inverted to make it ascending
lidar_ratio | path | /ScienceData/aerosol_layer_mean_lidar_ratio_355nm
description | the vertical grid is inverted to make it ascending
lidar_ratio_uncertainty | path | /ScienceData/aerosol_layer_mean_lidar_ratio_355nm_error
description | the vertical grid is inverted to make it ascending
linear_depolarization_ratio | path | /ScienceData/aerosol_layer_mean_depolarisation_355nm
description | the vertical grid is inverted to make it ascending
linear_depolarization_ratio_uncertainty | path | /ScienceData/aerosol_layer_mean_depolarisation_355nm_error
description | the vertical grid is inverted to make it ascending
validity | path | /ScienceData/quality_status
wavelength | description | set to fixed value of 355nm