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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, X X X X this is equal to 'aerosol optical thickness'
tropospheric
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, X X X X this is equal to 'aerosol optical thickness'
tropospheric
<aerosol_type>_aerosol_pressure X X
<aerosol_type>_aerosol_top_height X X
<aerosol_type>_aerosol_top_pressure X X
altitude sensor, X X X
surface
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, amf, apriori, X X X this is the mass density
tropospheric avk, dfs, sic
column_number_density stratospheric, amf, apriori, X X X
tropospheric avk, dfs, sic
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)
meridional_wind_velocity surface X X X
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
planetary_boundary_layer_height X X
potential_temperature surface X X X
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, X
surface, toa
solar_declination_angle
solar_elevation_angle sensor, X
surface, toa
solar_hour_angle
solar_irradiance X X
solar_zenith_angle sensor, X
surface, toa,
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
zonal_wind_velocity surface X X X
<species>_column_density stratospheric, amf, apriori, X X X this is the mass density
tropospheric avk, dfs, sic
<species>_slant_column_density X X this is the mass density
<pm>_column_density stratospheric, X X X this is the mass density
tropospheric
<species>_column_number_density stratospheric, amf, apriori, X X X
tropospheric avk, dfs, sic
<species>_slant_column_number_density X X
<species>_column_mass_mixing_ratio stratospheric, X X
tropospheric
<species>_column_mass_mixing_ratio_dry_air stratospheric, X X
tropospheric
<species>_column_volume_mixing_ratio stratospheric, X X
tropospheric
<species>_column_volume_mixing_ratio_dry_air stratospheric, X X
tropospheric
<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, X X X
dfs, sic
<species>_mass_mixing_ratio_dry_air surface apriori, avk, X X X
dfs, sic
<species>_number_density surface apriori, avk, X X X
dfs, sic
<species>_partial_pressure surface X X X
<species>_partial_pressure_dry_air surface X X X
<species>_volume_mixing_ratio surface apriori, avk, X X X this is equal to 'number mixing ratio'
dfs, sic
<species>_volume_mixing_ratio_dry_air surface apriori, avk, X X X
dfs, sic
============================================= =============== =============== ======= ==== ======= ===== =======================================================================
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, HCC-40, R-40
methyl chloride
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.
Surface wind velocity variables are actually near-surface wind velocities (usually at surface_altitude + 10m).
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 (:math:`x-y`)
- <variable>_diffrelx (:math:`\frac{x-y}{x}`)
- <variable>_diffrely (:math:`\frac{x-y}{y}`)
- <variable>_diffrelmin (:math:`\frac{x-y}{\min(x,y)}`)
- <variable>_diffrelmax (:math:`\frac{x-y}{\max(x,y)}`)
- <variable>_diffrelavg (:math:`\frac{2(x-y)}{x+y}`)
- <variable>_diffabs (:math:`|x-y|`)
- <variable>_diffabsrelx (:math:`\frac{|x-y|}{|x|}`)
- <variable>_diffabsrely (:math:`\frac{|x-y|}{|y|}`)
- <variable>_diffabsrelmin (:math:`\frac{|x-y|}{\min(|x|,|y|)}`)
- <variable>_diffabsrelmax (:math:`\frac{|x-y|}{\max(|x|,|y|)}`)
- <variable>_diffabsrelavg (:math:`\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.
The 'sic' postfix is used for the 'Shannon information content' for vertical profiles which can be derived from the
two-dimensional AVK.
|
