Dear Jonathan,
cf-metadata-bounces at cgd.ucar.edu schrieb am 31.10.2005 10:29:36:
> Dear Burkhardt
>
> Here are my responses to your standard name proposals, with apologies
for
> delay due to lack of time.
>
No need to apologize. I appreciate very much your effort in CF
conventions.
> Already in the table:
> > surface_snow_area_fraction 1
>
OK.
> 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
> OK and also requested by Keith Williams:
> > convective_cloud_area_fraction_in_atmosphere_layer 1
>
OK
> > 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
OK.
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?
OK.However, in the standard name table there is always (as far as I can
see) a unit defined. I suggest to use "s" as unit instead of "h".
duration_of_sunshine (s)
According to WMO definition sunshine occurs when direct solar radiation at
the surface exceeds 120 W m-2
>
> > 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?
>
This parameter is in fraction of volume. How can this be expressed? Can I
use X_volume_fraction like X_area_fraction which is already a valid
construction in the standard name table?
soil_moisture_volume_fraction_at_field_capacity (1)
> > 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.
>
OK.
soil_porosity (1)
> > 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.
Same comment as for field_capacity.
soil_moisture_volume_fraction_at_wilting_point (1)
>
> > 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?
>
Examples for land use are "urban, evergreen forests, cool rain forest,
wooded wet swamp" etc.
Thus it is a string variable.
Plotting programs may have problems with string variables. Is there a
possibility to map the string array to another that holds just numbers,
i.e. a fixed number for each string (for instance 1 = urbane, 2 =
evergreen forest, ...)?
land_use (1)
> > soil_type 1
> Similarly, how is this to be used?
>
Same comments as for land use. Examples for soil types are "rock, water,
loam, sandy-loam, sand, peat ...".
soil_type (1)
> > geostrophic_eastward_wind 1
> > geostrophic_northward_wind 1
> Names OK but shouldn't the units be m s-1?
>
You are right that is a typo.
geostrophic_eastward_wind (m s-1)
geostrophic_northward_wind (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?
>
Yes.
surface_downwelling_photosynthetic_radiative_flux_in_air (W m-2)
> > 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?
>
In some models grid scale clouds (i.e. for cloud cover = 1 in a grid box)
are treated differently from sub grid clouds (i.e. for cloud cover < 1).
Thus it makes sense to have the possibility to write them into the output
file seperately. Maybe it is better to use "sub_grid" instead of
"sub_scale".
sub_grid_mass_fraction_of_cloud_liquid_water_in_air (1)
sub_grid_mass_fraction_of_cloud_ice_in_air (1)
> > precipitation_water_loading 1 (mass fraction of rain plus snow in
> > air)
> Why not
> mass_fraction_of_precipitation_in_air
>
OK.
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.
>
Regarding your suggestions on horizontal divergence of energies (see
below) the standard name may be
tendency_of_atmosphere_water_content_due_to_advection (kg m-2)
> > 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?
>
That sounds good.
tendency_of_atmosphere_kinetic_energy_content_due_to_advection (W m-2)
tendency_of_atmosphere_potential_energy_content_due_to_advection (W m-2)
tendency_of_atmosphere_enthalpy_content_due_to_advection (W m-2)
> > 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?
>
Maybe this is too specific in our model. I therefore withdraw this
parameter and will use just a long name for our local interests.
> > 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.
>
OK
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)
> > 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.
>
That is a typo. m is correct.
dry_convection_top_altitude (m)
> > snow_fall_limit_altitude m
> Could you define this, please?
>
This is the altitude where the wet bulb temperature > 1.3 Celsius
(definition by Meteo Swiss). Thus snow does not melt instantaneously, when
it passes the 0 Celsius altitude. Therefore snow_level_limit_altitude is
fifferent from freezing_level_altitude.
snow_fall_limit_altitude (m)
> > deviation_from_reference_air_pressure Pa
> Could we make this
> difference_of_air_pressure_from_reference
> Is there a standard reference pressure?
>
There is no standard reference pressure. The reference pressure profile is
different amongst non-hydrostatic atmosphere models. Even for the same
model the users may define it seperately. The difference of pressure from
reference profile is often used as prognostic variable in non-hydrostatic
models instead of the total pressure. I guess because of numeric precision
reasons.
difference_of_air_pressure_from_reference (Pa)
> > 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).
>
OK
atmosphere_momentum_diffusivity (m2 s-1)
atmosphere_heat_diffusivity (m2 s-1)
> > convective_mass_flux kg m-2 s-1
> To be precise:
> atmosphere_convective_mass_flux
>
OK
atmosphere_convective_mass_flux (kg m-2 s-1)
> > 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.
>
Hmm... I must admit I am not really in this matter. I suggest to postpone
this. I have to ask the specialists first.
> > 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.
>
The measure is concentration (mol).
If I would use the existing standard name "mole_fraction_of_ozone_in_air"
and "cell_methods", how does cell_methods look like? Should it point to a
variable that defines the altitude of the mid of the atmosphere and the
corresponding bounds variable contains top and bottom of the atmosphere?
Or would a definition like "atmosphere_mole_fraction_of_ozone_maximum"
analogue to "atmosphere_water_content" do?
> > 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.
>
Units are in "Pa O3" but this is probably not CF conform since similar "m"
is used for soil moisture instead of "m H2O" in the standard name table.I
guess your suggestion makes sense.
equivalent_pressure_of_atmosphere_ozone_content (Pa)
> > 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.
>
In atmosphere models the maximum wind speed and the maximum wind speed due
to gusts are different. The first one is given by the models prognostic
wind as a maximum over the output interval (i.e. it has the attribute
cell_methods = "time: maximum").
Gusts are diagnosed every time step from the models prognostic wind speed
and other parameters.Then the maximum of the gusts is calculated over the
output interval. Thus this parameter needs a special standard name. If you
find a more appropriate one than the following, please let me know.
wind_speed_of_gusts (m s-1)
> > 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.
I was hesitating to propose this name because of the same arguments you
give. I am struggling a bit with the definition TOA. I assume this is the
"real" TOA not the model top? Our model is not at p=0 but at z=25km. That
means the downward longwave radiation at the top of our model is not zero.
I guess I should use the general names for upwelling and downwelling
fluxes (these are "OK as proposed" above) and add a height dimension that
contains just one number (25 in this case). Actually, it would be analogue
to definitions of 2metre temperature and 10metre wind. What do you think?
>
> > 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.
OK. I was not aware that this is a CF option. I thought every quantity
should be given a standard name. I will use just the long name.
>
> The lake standard names are in a separate email.
OK
Thank you
Regards
Burkhardt
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