[CF-metadata] new standard_names

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 31 Oct 2005 09:29:36 +0000

Dear Burkhardt

Here are my responses to your standard name proposals, with apologies for
delay due to lack of time.

Already in the table:
> surface_snow_area_fraction 1

OK as proposed:
> water_potential_evaporation_amount kg m-2
> runoff_amount kg m-2
> sea_ice_temperature K
> surface_geopotential m2 s-2
> surface_specific_humidity 1
> mass_fraction_of_rain_in_air 1
> mass_fraction_of_snow_in_air 1
> mass_fraction_of_graupel_in_air 1
> convective_cloud_base_altitude m
> convective_cloud_top_altitude m
> atmosphere_surface_drag_coefficient_of_momentum 1
> atmosphere_surface_drag_coefficient_of_heat 1
> lwe_thickness_of_frozen_water_content_of_soil_layer m
> coriolis_parameter s-1
> atmosphere_enthalpy_content J m-2
> atmosphere_potential_energy_content J m-2
> upwelling_shortwave_flux_in_air W m-2
> downwelling_shortwave_flux_in_air W m-2
> upwelling_longwave_flux_in_air W m-2
> downwelling_longwave_flux_in_air W m-2
> tendency_of_air_temperature_due_to_radiative_heating K s-1

OK and also requested by Keith Williams:
> convective_cloud_area_fraction_in_atmosphere_layer 1

> surface_downward_momentum_flux Pa
We currently have
  surface_downward_eastward_stress (Pa)
  surface_downward_northward_stress (Pa)
which are the components of the surface downward momentum flux. Do you mean
the magnitude of this vector? By the guidelines, it would be
  magnitude_of_surface_downward_stress

> sunshine_hours h
I suggest the name should not imply a specific unit of time. Could we call it
  duration_of_sunshine
Is there a well-defined threshold for sunshine which we could mention in the
definition as a default?

> field_capacity_of_soil 1
We already have a standard name
  soil_moisture_content_at_field_capacity (kg m-2)
What quantity related to this is dimensionless, as you propose? Perhaps it is
a fraction of saturation?

> porosity_of_soil 1
The commonly used phrase (on the web) appears to be
  soil_porosity (1)
which is consistent with other standard names e.g. soil_moisture_content,
soil_carbon_content.

> canopy_wilting_point 1
Does this mean the same as the wilting point i.e. the soil moisture content
below which plants will wilt? That would be
  soil_moisture_content_at_wilting_point (kg m-2)
Like the field capacity, it would not be dimensionless.

> land_use 1
I'm not sure what this means - could you please clarify? Is it an area
fraction or a type of land use? In the latter case, perhaps it is a string
variable?

> soil_type 1
Similarly, how is this to be used?

> geostrophic_eastward_wind 1
> geostrophic_northward_wind 1
Names OK but shouldn't the units be m s-1?

> surface_downwelling_photosynthetic_radiative_flux W m-2
We already have
surface_downwelling_photosynthetic_radiative_flux_in_sea_water. Is that what
you want or are you asking for _in_air?

> sub_scale_mass_fraction_of_cloud_liquid_water_in_air 1
> sub_scale_mass_fraction_of_cloud_ice_in_air 1
I'm not sure what sub_scale means - could you please clarify?

> precipitation_water_loading 1 (mass fraction of rain plus snow in
> air)
Why not
  mass_fraction_of_precipitation_in_air

> horizontal_divergence_of_mass_fraction_of_water_in_air kg m-2
This doesn't look right because mass_fraction_of_water_in_air is a
dimensionless scalar. We could have horizontal_divergence_of_product_of_wind_
and_mass_fraction_of_water_in_air (s-1) but if you want kg then maybe you
don't want mass_fraction.

> horizontal_divergence_of_atmosphere_kinetic_energy W m-2
> horizontal_divergence_of_atmosphere_enthalpy W m-2
> horizontal_divergence_of_atmosphere_potential_energy W m-2
Similarly, these need a velocity before we can calculate a divergence. But if
you mean the integral through the depth of the atmosphere of div(wind*X), then
it might be easier to describe these as tendency_of_X_due_to_advection, where
X is atmosphere_(kinetic_energy|potential_energy|enthalpy)_content. What do
you think?

> moisture_convergence_in_the_air_for_kuo_type_closure m s-1
>From the units it is unclear what meaning of moisture is being used here: I
think it should be s-1 or kg m-3 s-1. Could you clarify? What is specific
to the Kuo scheme?

> layer_index_at_convective_cloud_base 1
> layer_index_at_convective_cloud_top 1
> model_layer_index_of_atmosphere_boundary_layer_top 1
Since we have a standard name of model_level_number, which says that "level"
and "layer" mean the same thing, these should be
  model_level_number_at_convective_cloud_base (1)
  model_level_number_at_convective_cloud_top (1)
  model_level_number_at_top_of_atmosphere_boundary_layer (1)
where I am suggesting an unpacked version of the layer name.

> dry_convection_top_altitude 1
I think I would suggest an unpacked version of this:
  altitude_at_top_of_dry_convection
The units should be m.

> snow_fall_limit_altitude m
Could you define this, please?

> deviation_from_reference_air_pressure Pa
Could we make this
  difference_of_air_pressure_from_reference
Is there a standard reference pressure?

> diffusion_coefficient_of_momentum m2 s-1
> diffusion_coefficient_of_heat m2 s-1
Since we have already used "diffusivity" in a standard name, let's call these
  atmosphere_momentum_diffusivity
  atmosphere_heat_diffusivity
I assume you mean atmosphere (not ocean).

> convective_mass_flux kg m-2 s-1
To be precise:
  atmosphere_convective_mass_flux

> square_root_of_two_times_turbulent_kinetic_energy m s-1
> convective_turbulent_kinetic_energy J kg-1
How are you defining the mean velocity with respect to which the TKE is
calculated? How do you separate the part of it associated with convection? It
seems to me that TKE is rather a generic concept which has to be specified
more precisely for a standard name.

> air_pressure_at_ozone_maximum Pa
What measure of ozone is maximal? - is it concentration (mol or kg m-3)?
I think it might be possible to describe "at ozone maximum" with an entry
in cell_methods.

> atmosphere_ozone_content Pa
The atmosphere_ozone_content would be in kg m-2. Is that what you want? If you
wish to express it as Pa i.e. its weight, perhaps it should be called
equivalent_pressure_of_atmosphere_ozone_content, like the equivalent
thickness. It's not the partial pressure as it's not well-mixed.

> wind_speed_of_gust m s-1
A gust is a maximum wind speed within some time interval. How is this quantity
used? If it's a timeseries of gust speed, for instance, then the standard name
of wind_speed with a cell_methods indicating it was the maximum within the
time-interval would be appropriate.

> toa_net_downward_longwave_flux W m-2
Just to check - is there really a need for this? There is no downwelling LW
flux at TOA (apart from cosmic microwave background!) so this = - TOA outgoing
LW flux.

> normalized_cloud_depth 1 (cloud depth to 0-1 for TV presentations)
> modified_cloud_area_fraction 1 ( Computation of the total cloud
> cover by minimum overlapping and multiply it by an empirical 'red'-
> factor for TV presentations)
It sounds like these are quantities of local interest, rather than of general
interest for exchanging and archiving data. Is that fair? If so, they could be
distinguished by your software using the long_name, for example.

The lake standard names are in a separate email.

Best wishes

Jonathan
Received on Mon Oct 31 2005 - 02:29:36 GMT