# Nitrogen Data Fields

## NO2 Concentration

The NO2 concentration field and associated error are given in units of mol/m3. Multiply by $$6.02214076 \times 10^{17}$$ to convert these fields to units of molecules/cm3.

NO2_concentration

Mole concentration of NO2 in units of mol/m3. Only converged values in the retrieval range and above any cloud layer are reported.

The associated error in the retrieved NO2 is given by:

NO2_concentration_standard_error

Standard uncertainty of the retrieved NO2 concentration in units of mol/m3.

The vertical resolution is computed for every retrieved profile from the FWHM of the averaging kernel and is given by:

vertical_resolution

FWHM of the averaging kernel, with units of km.

Although not recommended for general use, the field _rtm_internal_NO2_concentration may be useful in investigating possible biases due to retrieval saturation or other similar effects. This field includes altitudes affected by clouds and those that have not fully converged.

_rtm_internal_NO2_concentration

The full ozone concentration profile as used in the SASKTRAN radiative transfer model in units of mol/m3.

## Derived Nitrogen Products

Including in the nitrogen files are additional NO, NO2, and NOx profiles derived from the retrieved NO2 and shifted to different times of the day using the PRATMO photochemical box model. These are:

derived_0630_NO2_concentration

Mole concentration of NO2 shifted to a local solar time of 06:30 in units of mol/m3.

derived_daily_mean_NO2_concentration

Daily mean of mole concentration of NO2 in units of mol/m3.

derived_1200_NO2_concentration

Mole concentration of NO2 shifted to local solar noon in units of mol/m3.

derived_local_solar_time_NO_concentration

Mole concentration of NO at the local solar time of the measurement in units of mol/m3.

derived_0630_NO_concentration

Mole concentration of NO shifted to a local solar time of 06:30 in units of mol/m3.

derived_daily_mean_NO_concentration

Daily mean of NO in units of mol/m3.

derived_1200_NO_concentration

Mole concentration of NO shifted to local solar noon in units of mol/m3.

derived_local_solar_time_NOx_concentration

Mole concentration of NOx at the local solar time of the measurement in units of mol/m3.

derived_0630_NOx_concentration

Mole concentration of NOx shifted to a local solar time of 06:30 in units of mol/m3.

derived_daily_mean_NOx_concentration

Daily mean of NOx in units of mol/m3.

derived_1200_NOx_concentration

Mole concentration of NOx shifted to local solar noon in units of mol/m3.

## Clouds

The cloud altitudes retrieved during the aerosol extinction retrieval. Clouds are separated into two categories:

cloud_top_altitude

The altitude, in km, of the top of a cloud detected in this profile, NaN otherwise

psc_altitude

The altitude, in km, of a polar stratospheric cloud detected in this profile, NaN otherwise

Note

While the ozone concentration is reported in _rtm_internal_NO2_concentration when clouds are flagged, it is unlikely to be a reliable quantitative measure, as assumptions made in the retrieval are not consistent with cloud microphysics.

## Meteorology

A few meteorological fields are included in the data to aid in analysis.

temperature

Temperature taken from MERRA 2 and interpolated to the current geometrical altitude grid.

pressure

Pressure in hPa taken from MERRA 2 and interpolated to the current geometrical altitude grid.

tropopause_altitude

Tropopause in km based on WMO lapse-rate tropopause definition; the first parameter for the lowest tropopause.Calculated from MERRA 2 temperature profiles.

## Geometry

For ease of use, each OSIRIS scan is assigned to a specific geographic location and time. This is not strictly true, as a scan takes approximately 90 seconds to complete and spans a few degrees latitude over this time. The geometric data fields are defined at the 30 km point of each scan.

latitude

latitude in degrees north

longitude

longitude in degrees east

time

days since 1900-01-01 00:00:00

local_solar_time

Local solar time in hours

In addition to the geographic location, three solar angles are provided that define the measurement geometry of the line of sight with respect to sun.

ssa

Solar scattering angle. The angle between the line of sight and the solar beam.

sza

Solar zenith angle. The angle between solar beam and the vertical direction at the tangent point.

saa

Solar azimuth angle. The angle between the horizontal projection of the solar beam and the line of sight.

albedo

The retrieved albedo of the surface.

## Retrieval

These fields provide information about the retrieved NO2 concentration profiles. It should be noted that values below retrieval_lowerbound are truncated from NO2_concentration. Profiles with poor convergence are also filtered from this product.

retrieval_lowerbound

Lowest altitude in km that is valid for the NO2 retrieval.

convergence_ratio

Convergence ratio of the NO2 retrieval.

chi_sq

The $${\chi}$$2 value of the NO2 retrieval.