Variable names
To allow HARP to perform automatic operations on variables, it imposes a strict naming convention for variables. This
naming convention applies to the variable name itself and is therefore fully complementary to naming conventions that
apply to the value of a variable attribute, such as standard_name
(as specified by netCDF-CF).
Note that it is possible to use variables inside HARP products with names that do not follow the convention, but then these variables may not be handled correctly by operations that you perform on the product. The general rule is that if you have a quantity that can be represented by the naming convention below then you should use the HARP variable name for it.
HARP defines the following variable names:
Name | Prefixes | Postfixes | Quality | Vert | Lat/Lon | Spect | Comments |
---|---|---|---|---|---|---|---|
absolute_vorticity | X | X | X | ||||
absorbing_aerosol_index | X | X | |||||
aerosol_base_height | X | X | |||||
aerosol_base_pressure | X | X | |||||
aerosol_extinction_coefficient | surface | X | X | X | X | ||
aerosol_height | X | X | |||||
aerosol_optical_depth | stratospheric, tropospheric | X | X | X | X | this is equal to ‘aerosol optical thickness’ | |
aerosol_pressure | X | X | |||||
aerosol_top_height | X | X | |||||
aerosol_top_pressure | X | X | |||||
<aerosol_type>_aerosol_base_height | X | X | |||||
<aerosol_type>_aerosol_base_pressure | X | X | |||||
<aerosol_type>_aerosol_extinction_coefficient | surface | X | X | X | X | ||
<aerosol_type>_aerosol_height | X | X | |||||
<aerosol_type>_aerosol_optical_depth | stratospheric, tropospheric | X | X | X | X | this is equal to ‘aerosol optical thickness’ | |
<aerosol_type>_aerosol_pressure | X | X | |||||
<aerosol_type>_aerosol_top_height | X | X | |||||
<aerosol_type>_aerosol_top_pressure | X | X | |||||
altitude | sensor, surface | X | X | X | |||
altitude_bounds | X | X | X | ||||
area | X | the size of an area defined by latitude/longitude bounds | |||||
backscatter_coefficient | surface | X | X | X | X | ||
cloud_albedo | X | X | |||||
cloud_base_albedo | X | X | |||||
cloud_base_height | X | X | |||||
cloud_base_pressure | X | X | |||||
cloud_base_temperature | X | X | |||||
cloud_fraction | X | X | |||||
cloud_height | X | X | |||||
cloud_optical_depth | X | X | this is equal to ‘cloud optical thickness’ | ||||
cloud_pressure | X | X | |||||
cloud_temperature | X | X | |||||
cloud_top_albedo | X | X | |||||
cloud_top_height | X | X | |||||
cloud_top_pressure | X | X | |||||
cloud_top_temperature | X | X | |||||
collocation_index | zero-based index as provided in the collocation result file | ||||||
column_density | stratospheric, tropospheric | amf, apriori, avk, dfs | X | X | X | this is the mass density | |
column_number_density | stratospheric, tropospheric | amf, apriori, avk, dfs | X | X | X | ||
count | |||||||
datetime | |||||||
datetime_length | |||||||
datetime_start | |||||||
datetime_stop | |||||||
density | X | X | X | this is the mass density | |||
extinction_coefficient | surface | X | X | X | X | ||
frequency | X | ||||||
frequency_irradiance | X | X | |||||
frequency_photon_irradiance | X | X | |||||
frequency_photon_radiance | X | X | |||||
frequency_photon_transmittance | X | X | |||||
frequency_radiance | X | X | |||||
frequency_transmittance | X | X | |||||
geoid_height | X | X | |||||
geopotential | surface | X | X | X | |||
geopotential_height | surface | X | X | X | |||
hlos_wind_velocity | surface | X | X | X | hlos means ‘horizontal line of sight’ | ||
index | zero-based index of the sample within the source product | ||||||
integration_time | X | X | X | provides measurement specific integration time (at e.g. altitude or wavelength) compared to overal datetime_length; only use if integration time differs from datetime_length; integration_time longer than datetime_length that covers multiple datetime values means replication of measured value in time dimension | |||
latitude | sensor | X | (lat) | ||||
latitude_bounds | (lat) | ||||||
longitude | sensor | X | (lon) | ||||
longitude_bounds | (lon) | ||||||
molar_mass | X | X | X | this is the molar mass of the total substance (it is defined by the relation between the variables ‘density’ and ‘number_density’) | |||
month | category variable for month of year (‘January’, ..., ‘December’) | ||||||
number_density | surface | X | X | X | |||
optical_depth | X | X | X | X | this is equal to ‘optical thickness’ | ||
orbit_index | the absolute orbit number for data from polar orbiting satellites | ||||||
pressure | surface | X | X | X | |||
pressure_bounds | X | X | X | ||||
radiance | X | X | |||||
reflectance | X | X | |||||
relative_azimuth_angle | X | absolute difference between sensor and solar azimuth angles | |||||
relative_humidity | X | X | X | ||||
relative_vorticity | X | X | X | ||||
scan_direction_type | |||||||
scan_subindex | |||||||
scattering_angle | X | ||||||
sensor_azimuth_angle | X | ||||||
sensor_elevation_angle | X | ||||||
sensor_name | used mainly for ground based networks to provide a unique sensor id | ||||||
sensor_zenith_angle | X | ||||||
site_name | used for data of a specific named geographical location | ||||||
solar_azimuth_angle | sensor, surface, toa | X | |||||
solar_declination_angle | |||||||
solar_elevation_angle | sensor, surface, toa | X | |||||
solar_hour_angle | |||||||
solar_irradiance | X | X | |||||
solar_zenith_angle | sensor, surface, toa, | X | |||||
sun_normalized_radiance | X | X | |||||
surface_albedo | X | X | X | ||||
temperature | surface | X | X | X | |||
tropopause_altitude | X | X | altitude of the troposphere/stratosphere boundary location | ||||
tropopause_pressure | X | X | pressure level of the troposphere/stratosphere boundary location | ||||
validity | validity flag for each time sample or whole product; only to be used if validity flag is for multiple variables combined | ||||||
viewing_azimuth_angle | X | ||||||
viewing_elevation_angle | X | ||||||
viewing_zenith_angle | X | ||||||
virtual_temperature | X | X | X | ||||
wavelength | X | X | |||||
wavelength_irradiance | X | X | |||||
wavelength_photon_irradiance | X | X | |||||
wavelength_photon_radiance | X | X | |||||
wavelength_photon_transmittance | X | X | |||||
wavelength_radiance | X | X | |||||
wavelength_transmittance | X | X | |||||
wavenumber | X | X | |||||
wavenumber_irradiance | X | X | |||||
wavenumber_photon_irradiance | X | X | |||||
wavenumber_photon_radiance | X | X | |||||
wavenumber_photon_transmittance | X | X | |||||
wavenumber_radiance | X | X | |||||
wavenumber_transmittance | X | X | |||||
wind_speed | surface | X | X | X | |||
wind_direction | surface | X | X | X | |||
year | integer value representing a year | ||||||
<species>_column_density | stratospheric, tropospheric | amf, apriori, avk, dfs | X | X | X | this is the mass density | |
<species>_slant_column_density | X | X | this is the mass density | ||||
<pm>_column_density | stratospheric, tropospheric | X | X | X | this is the mass density | ||
<species>_column_number_density | stratospheric, tropospheric | amf, apriori, avk, dfs | X | X | X | ||
<species>_slant_column_number_density | X | X | |||||
<species>_column_mass_mixing_ratio | stratospheric, tropospheric | X | X | ||||
<species>_column_mass_mixing_ratio_dry_air | stratospheric, tropospheric | X | X | ||||
<species>_column_volume_mixing_ratio | stratospheric, tropospheric | X | X | ||||
<species>_column_volume_mixing_ratio_dry_air | stratospheric, tropospheric | X | X | ||||
<species>_density | surface | X | X | X | this is the mass density | ||
<pm>_density | surface | X | X | X | this is the mass density | ||
O3_effective_temperature | X | X | |||||
<species>_mass_mixing_ratio | surface | apriori, avk, dfs | X | X | X | ||
<species>_mass_mixing_ratio_dry_air | surface | apriori, avk, dfs | X | X | X | ||
<species>_number_density | surface | apriori, avk, dfs | X | X | X | ||
<species>_partial_pressure | surface | X | X | X | |||
<species>_partial_pressure_dry_air | surface | X | X | X | |||
<species>_volume_mixing_ratio | surface | apriori, avk, dfs | X | X | X | this is equal to ‘number mixing ratio’ | |
<species>_volume_mixing_ratio_dry_air | surface | apriori, avk, dfs | X | X | X |
The supported aerosol types are:
Aerosol type | Description |
---|---|
sea_salt | sea salt |
dust | dust |
organic_matter | organic matter |
black_carbon | black carbon |
sulphate | sulphate |
The supported PM (particulate matter) types are:
Name | Description |
---|---|
PM1 | particulate matter with d < 1 um |
PM2p5 | particulate matter with d < 2.5 um |
PM10 | particulate matter with d < 10 um |
The supported species are:
Name | Description | Aliases (not used by HARP) |
---|---|---|
dry_air | dry air | |
BrO | bromine oxide | |
BrO2 | bromine dioxide | |
CCl2F2 | dichlorodifluoromethane | freon-12, CFC-12, R-12, F12 |
CCl3F | trichlorofluoromethane | freon-11, CFC-11, R-11, F11 |
CCl4 | tetrachloromethane | |
CF4 | tetrafluoromethane | CFC-14, F14 |
CHClF2 | chlorodifluoromethane | HCFC-22, R-22, F22 |
CH3Cl | chloromethane, methyl chloride | HCC-40, R-40 |
CH3CN | acetonitrile, methyl cyanide | |
CH3OH | methanol | |
CH4 | methane | |
CO | carbon monoxide | |
COF2 | carbonyl fluoride | |
COS | carbonyl sulfide | OCS |
CO2 | carbon dioxide | |
C2H2 | acetylene | HCCH |
C2H2O2 | glyoxal | OCHCHO, CHOCHO |
C2H3NO5 | peroxyacetyl nitrate | PAN |
C2H6 | ethane | |
C3H8 | propane | |
C5H8 | isoprene | |
ClNO3 | chlorine nitrate | |
ClO | chlorine monoxide | |
HCHO | formaldehyde | CH2O, H2CO |
HCOOH | formic acid | HCO2H |
HCN | hydrogen cyanide | |
HCl | hydrogen chloride | |
HF | hydrogen fluoride | |
HNO2 | nitrous acid | |
HNO3 | nitric acid | |
HNO4 | peroxynitric acid | |
HOCl | hypochlorous acid | |
HO2 | hydroperoxyl | |
H2O | water | |
H2O_161 | water (H1/O16/H1 isotopes) | |
H2O_162 | water (H1/O16/H2 isotopes) | HDO |
H2O_171 | water (H1/O17/H1 isotopes) | |
H2O_181 | water (H1/O18/H1 isotopes) | |
H2O2 | hydrogen peroxide | |
IO | hypoiodite | |
IWC | ice water content; H2O in ice state | |
LWC | liquid water content; H2O in liquid state | |
NH3 | ammonia | |
NO | nitric oxide | |
NOCl | nitrosyl chloride | |
NO2 | nitrogen dioxide | |
NO3 | nitrate | |
N2 | nitrogen gas | |
N2O | nitrous oxide | NOS |
N2O5 | dinitrogen pentoxide | |
OClO | chlorine dioxide | ClO2 |
OH | hydroxyl | |
O2 | oxygen | |
O3 | ozone | |
O3_666 | ozone (O16/O16/O16 isotopes) | |
O3_667 | ozone (O16/O16/O17 isotopes) | |
O3_668 | ozone (O16/O16/O18 isotopes) | |
O3_686 | ozone (O16/O18/O16 isotopes) | |
O4 | tetraoxygen, oxozone | |
SF6 | sulfur hexafluoride | |
SO2 | sulfur dioxide |
Variables for which a prefix and/or postfix is provided can have any of the given prefixes and/or any of the given postfixes (separated by underscores). It is not allowed to provide more than one prefix or more than one postfix. Variables having an ‘X’ in the Quality column can have any of the following additional versions of the variable (where <variable> can include any of the allowed prefix and/or postfix combinations):
- <variable>_covariance
- <variable>_uncertainty
- <variable>_uncertainty_random
- <variable>_uncertainty_systematic
- <variable>_validity
Some examples of valid variable names are: tropospheric_O3_column_number_density
,
tropospheric_O3_column_number_density_apriori
, O3_column_number_density_apriori
,
tropospheric_O3_column_number_density_uncertainty
, O3_column_number_density_apriori_uncertainty
.
The Vert, Lat/Lon, and Spec columns indicate whether a variable can be dependent on the vertical
,
latitude
& longitude
, and/or spectral
dimensions (any variable can be dependent on the time
dimension).
The ‘surface’ prefix should only be used when quantities are combined together with quantities that have a vertical dimension. If a product just contains surface quantities then don’t use a ‘surface’ prefix but just omit the vertical dimension and indicate the vertical level (i.e. location of the surface) using a ‘pressure’, ‘altitude’, and/or ‘geopotential_height’ variable.
All (horizontal) azimuth angles in HARP should follow the convention that 0 is North facing and the angle is increasing when moving Eastwards (i.e. clockwise). Wind direction follows the same rules as for azimuth angles (North = 0, East = 90 degrees), but the direction indicates where the wind is coming from.
In addition to the conventions above there can also be variables that describe a ‘difference’. These difference variables can only be used to describe differences of the same quantity between different datasets (‘x’ and ‘y’) and only for variables that have a unit. All difference variables in a single product should apply to the same datasets ‘x’ and ‘y’ (i.e. the difference variables should only reflect a single comparison of datasets; you should not combine one difference variable for ‘x-y’ and another for ‘x-z’ (even for different quantities) within the same product). A difference variable is indicated by a postfix. The ‘difference postfix’ can come before a ‘quality postfix’ if we are talking about the ‘quality of the difference’. If the ‘difference postfix’ comes after a ‘quality postfix’ then we are talking about the ‘difference of the quality quantity’. The supported differences are:
- <variable>_diff (\(x-y\))
- <variable>_diffrelx (\(\frac{x-y}{x}\))
- <variable>_diffrely (\(\frac{x-y}{y}\))
- <variable>_diffrelmin (\(\frac{x-y}{\min(x,y)}\))
- <variable>_diffrelmax (\(\frac{x-y}{\max(x,y)}\))
- <variable>_diffrelavg (\(\frac{2(x-y)}{x+y}\))
- <variable>_diffabs (\(|x-y|\))
- <variable>_diffabsrelx (\(\frac{|x-y|}{|x|}\))
- <variable>_diffabsrely (\(\frac{|x-y|}{|y|}\))
- <variable>_diffabsrelmin (\(\frac{|x-y|}{\min(|x|,|y|)}\))
- <variable>_diffabsrelmax (\(\frac{|x-y|}{\max(|x|,|y|)}\))
- <variable>_diffabsrelavg (\(\frac{2|x-y|}{|x+y|}\))
The postfix ‘avk’ is used for averaging kernels of atmospheric vertical profiles. An AVK that only depends once on the vertical dimension is a column averaging kernel, and an AVK that depends twice on the vertical dimension is a profile averaging kernel. The ‘amf’ postfix is used for air mass factors. The ‘dfs’ postfix is used for the ‘degree of freedom for signal’ for vertical profiles which equals the trace or diagonal of the two-dimensional AVK and provides information on the vertical resolution and information content of profiles.