# OMI_L2_OMDOMINO

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `OMI_L2_OMDOMINO` data.

field name | type | dimensions | unit | description
--- | --- | --- | --- | ---
datetime | double | {time} | [seconds since 2000-01-01] | time of the measurement
longitude | double | {time} | [degree_east] | longitude of the ground pixel center
latitude | double | {time} | [degree_north] | latitude of the ground pixel center
longitude_bounds | double | {time, 4} | [degree_east] | longitudes of the ground pixel corners
latitude_bounds | double | {time, 4} | [degree_north] | latitudes of the ground pixel corners
solar_zenith_angle | double | {time} | [degree] | solar zenith angle at WGS84 ellipsoid for center co-ordinate of the ground pixel
solar_azimuth_angle | double | {time} | [degree] | solar azimuth angle at WGS84 ellipsoid for center co-ordinate of the ground pixel, defined East-of-North
viewing_zenith_angle | double | {time} | [degree] | viewing zenith angle at WGS84 ellipsoid for center co-ordinate of the ground pixel
viewing_azimuth_angle | double | {time} | [degree] | viewing azimuth angle at WGS84 ellipsoid for center co-ordinate of the ground pixel, defined East-of-North
NO2_column_number_density | double | {time} | [molec/cm^2] | NO2 vertical column density
NO2_column_number_density_uncertainty | double | {time} | [molec/cm^2] | uncertainty of the NO2 vertical column density
tropospheric_NO2_column_number_density | double | {time} | [molec/cm^2] | NO2 tropospheric column density
tropospheric_NO2_column_number_density_uncertainty | double | {time} | [molec/cm^2] | uncertainty of the NO2 tropospheric column density
tropospheric_NO2_column_number_density_validity | int16 | {time} |  | flags describing the NO2 tropospheric column processing quality
cloud_fraction | double | {time} | [] | effective cloud fraction
cloud_fraction_uncertainty | double | {time} | [] | uncertainty of the effective cloud fraction
cloud_pressure | double | {time} | [hPa] | effective cloud pressure
cloud_pressure_uncertainty | double | {time} | [hPa] | uncertainty of the effective cloud pressure
index | int32 | {time} |  | zero-based index of the sample within the source product

## Mapping description

The shape and size of each ground pixel is not included in the product. HARP therefore provides its own approximation which is based on interpolation of the available center coordinates for each of the ground pixels. Each corner coordinate is determined by its four surrounding center coordinates. The corner coordinate is exactly at the intersection of the cross that can be made with these four points (each line of the cross is the great-circle distance from one center coordinate to the other). In situations where a corner coordinate is not surrounded by four center coordinates (i.e. at the boundaries) virtual center coordinates are created by means of extrapolation. The virtual center coordinate is placed such that the distance to its nearest real center coordinate equals the distance between that nearest real center coordinate and the next center coordinate going further inwards. In mathematical notation: when c(i,m+1) is the virtual center coordinate and c(i,m) and c(i,m-1) are real center coordinates, then ||c(i,m+1) - c(i,m)|| = ||c(i,m) - c(i,m-1)|| and all three coordinates should lie on the same great circle. The four virtual coordinates that lie in the utmost corners of the boundaries are calculated by extrapolating in a diagonal direction (e.g. c(n+1,m+1) is calculated from c(n,m) and c(n-1,m-1)).

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

field name | mapping description
--- | ---
datetime | path | /HDFEOS/SWATHS/DominoNO2/Geolocation_Fields/Time[]
description | the time of the measurement converted from TAI93 to seconds since 2000-01-01T00:00:00
longitude | path | /HDFEOS/SWATHS/DominoNO2/Geolocation_Fields/Longitude[]
latitude | path | /HDFEOS/SWATHS/DominoNO2/Geolocation_Fields/Latitude[]
longitude_bounds | path | /HDFEOS/SWATHS/DominoNO2/Geolocation_Fields/LongitudeCornerpoints[]
description | corners are reordered from {a,b,c,d} to {d,b,a,c}
latitude_bounds | path | /HDFEOS/SWATHS/DominoNO2/Geolocation_Fields/LatitudeCornerpoints[]
description | corners are reordered from {a,b,c,d} to {d,b,a,c}
solar_zenith_angle | path | /HDFEOS/SWATHS/DominoNO2/Geolocation_Fields/SolarZenithAngle[]
solar_azimuth_angle | path | /HDFEOS/SWATHS/DominoNO2/Geolocation_Fields/SolarAzimuthAngle[]
viewing_zenith_angle | path | /HDFEOS/SWATHS/DominoNO2/Geolocation_Fields/ViewingZenithAngle[]
viewing_azimuth_angle | path | /HDFEOS/SWATHS/DominoNO2/Geolocation_Fields/ViewingAzimuthAngle[]
NO2_column_number_density | path | /HDFEOS/SWATHS/DominoNO2/Data_Fields/TotalVerticalColumn[]
NO2_column_number_density_uncertainty | path | /HDFEOS/SWATHS/DominoNO2/Data_Fields/TotalVerticalColumnError[]
tropospheric_NO2_column_number_density | path | /HDFEOS/SWATHS/DominoNO2/Data_Fields/TroposphericVerticalColumn[]
tropospheric_NO2_column_number_density_uncertainty | path | /HDFEOS/SWATHS/DominoNO2/Data_Fields/TroposphericVerticalColumnError[]
tropospheric_NO2_column_number_density_validity | path | /HDFEOS/SWATHS/DominoNO2/Data_Fields/TroposphericColumnFlag[]
description | data is converted from uint8 to int16
cloud_fraction | path | /HDFEOS/SWATHS/DominoNO2/Data_Fields/CloudFraction[]
cloud_fraction_uncertainty | path | /HDFEOS/SWATHS/DominoNO2/Data_Fields/CloudFractionStd[]
cloud_pressure | path | /HDFEOS/SWATHS/DominoNO2/Data_Fields/CloudPressure[]
cloud_pressure_uncertainty | path | /HDFEOS/SWATHS/DominoNO2/Data_Fields/CloudPressureStd[]