# OMI_L3_OMNO2d

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `OMI_L3_OMNO2d` data.

field name | type | dimensions | unit | description
--- | --- | --- | --- | ---
datetime_start | double | {time} | [seconds since 2000-01-01] | start time of the grid
datetime_length | double | {time} | [days] | length of the grid
longitude | double | {longitude} | [degree_east] | longitude of the grid cell mid-point (WGS84)
latitude | double | {latitude} | [degree_north] | latitude of the grid cell mid-point (WGS84)
NO2_column_number_density | double | {time, latitude, longitude} | [molec/cm2] | NO2 vertical column density
tropospheric_NO2_column_number_density | double | {time, latitude, longitude} | [molec/cm2] | NO2 tropospheric column density
index | int32 | {time} |  | zero-based index of the sample within the source product

## Ingestion options

The table below lists the available ingestion options for `OMI_L3_OMNO2d` products.

option name | legal values | description
--- | --- | ---
no2 | cloud_screened | whether to ingested the unfiltered NO2 (default) or cloud screened NO2 (no2=cloud_screened) data

## Mapping description

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

field name | mapping description
--- | ---
datetime_start | path | /HDFEOS/ADDITIONAL/FILE_ATTRIBUTES@TAI93At0zOfGranule
description | the time of the measurement converted from TAI93 to seconds since 2000-01-01T00:00:00
datetime_length | description | set to fixed value of 1
longitude | path | /HDFEOS/GRIDS/ColumnAmountNO2@GridSpacing, /HDFEOS/GRIDS/ColumnAmountNO2@NumberOfLongitudesInGrid
description | a uniformly increasing sequence on the interval (-180, 180)
latitude | path | /HDFEOS/GRIDS/ColumnAmountNO2@GridSpacing, /HDFEOS/GRIDS/ColumnAmountNO2@NumberOfLatitudesInGrid
description | a uniformly increasing sequence on the interval (-90, 90)
NO2_column_number_density | condition | no2 unset
path | /ColumnAmountNO2[]
condition | no2=cloud_screened
path | /ColumnAmountNO2CloudScreened[]
tropospheric_NO2_column_number_density | condition | no2 unset
path | /ColumnAmountNO2Trop[]
condition | no2=cloud_screened
path | /ColumnAmountNO2TropCloudScreened[]