OMI_L2_OMHCHO
Variables
The table below lists the variables that are present in the HARP product that results from an ingestion of OMI_L2_OMHCHO
data.
field name 
type 
dimensions 
unit 
description 

datetime 
double 
{time} 
[seconds since 20000101] 
time of the measurement 
longitude 
double 
{time} 
[degree_east] 
longitude of the ground pixel center (WGS84) 
latitude 
double 
{time} 
[degree_north] 
latitude of the ground pixel center (WGS84) 
longitude_bounds 
double 
{time, 4} 
[degree_east] 
longitudes of the ground pixel corners (WGS84) 
latitude_bounds 
double 
{time, 4} 
[degree_north] 
latitudes of the ground pixel corners (WGS84) 
HCHO_column_number_density 
double 
{time} 
[molec/cm^2] 
HCHO vertical column density 
HCHO_column_number_density_uncertainty 
double 
{time} 
[molec/cm^2] 
uncertainty of the HCHO vertical column density 
index 
int32 
{time} 
zerobased index of the sample within the source product 
Ingestion options
The table below lists the available ingestion options for OMI_L2_OMHCHO
products.
option name 
legal values 
description 

destriped 
true 
ingest column densities without destriping correction (default) or with destriping correction (destriped=true) 
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 greatcircle 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,m1) are real center coordinates, then c(i,m+1)  c(i,m) = c(i,m)  c(i,m1) 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(n1,m1)).
The table below details where and how each variable was retrieved from the input product.
field name 
mapping description 


datetime 
path 
/HDFEOS/SWATHS/OMI_Total_Column_Amount_HCHO/Geolocation_Fields/Time[] 
description 
the time of the measurement converted from TAI93 to seconds since 20000101T00:00:00 

longitude 
path 
/HDFEOS/SWATHS/OMI_Total_Column_Amount_HCHO/Geolocation_Fields/Longitude[] 
latitude 
path 
/HDFEOS/SWATHS/OMI_Total_Column_Amount_HCHO/Geolocation_Fields/Latitude[] 
longitude_bounds 
description 
interpolated from the available center coordinates for each of the ground pixels 
latitude_bounds 
description 
interpolated from the available center coordinates for each of the ground pixels 
HCHO_column_number_density 
condition 
destriped unset 
path 
/HDFEOS/SWATHS/OMI_Total_Column_Amount_HCHO/Data_Fields/ColumnAmount[] 

condition 
destriped=true 

path 
/HDFEOS/SWATHS/OMI_Total_Column_Amount_HCHO/Data_Fields/ColumnAmountDestriped[] 

HCHO_column_number_density_uncertainty 
available 
optional 
condition 
destriped unset 

path 
/HDFEOS/SWATHS/OMI_Total_Column_Amount_HCHO/Data_Fields/ColumnUncertainty[] 