Fair enough Jonathon.. Ok, then to ensure consistency with current expressions can I then request the following variable names (I've added two more..):
change_over_time_in_sea_water_salinity change_over_time_in_sea_water_temperature change_over_time_in_sea_water_potential_temperature change_over_time_in_sea_water_density change_over_time_in_sea_water_potential_density change_over_time_in_sea_water_neutral_density Cheers, P -----Original Message----- From: Jonathan Gregory [mailto:[email protected]] Sent: Thursday, April 14, 2011 6:06 PM To: Durack, Paul (CMAR, Hobart) Cc: [email protected] Subject: Re: [CF-metadata] [Standard name request] property changes over time Dear Paul We don't see to be speaking the same language. As I understand it these four quantities you are proposing should all be change_over_time_in_X. That's what they are, isn't it? > sea_water_salinity_change > sea_water_temperature_change > sea_water_potential_temperature_change > sea_water_density_change change_over_time_in_sea_water_salinity etc. would be consistent with these names that you pointed out: > change_over_time_in_atmosphere_water_content_due_to_advection > change_over_time_in_surface_snow_amount These quantities are not changes over time: > change_in_atmosphere_energy_content_due_to_change_in_sigma_coordinate_wrt_surface_pressure > change_in_energy_content_of_atmosphere_layer_due_to_change_in_sigma_coordinate_wrt_surface_pressure These quantities have _change at the end because in their case, unusually, the quantity doesn't make sense as an "absolute" value, but only as a change. That is, there is no such quantity as "global average thermosteric sea level" for instance. That's why these names are not change_over_time_in: > global_average_sea_level_change > global_average_steric_sea_level_change > global_average_thermosteric_sea_level_change These quantities (and many other others) are all time-derivatives, for which we consistently use the phrase tendency_of: > tendency_of_air_density > tendency_of_air_pressure > tendency_of_air_temperature That is not the same as change_over_time_in because it's got different physical dimensions (units). A tendency is a change_over_time divided by the length of the time interval (for infinitesimal intervals, anyway). The CF standard names have canonical units, defining their physical dimensions, and quantities always have different standard names if their physical dimensions differ. Hence we could not have the same standard name for change_over_time and tendency quantities. In summary, I think the variety of expressions we have used in existing standard names is quite systematic and indicates meaningful distinctions. Best wishes Jonathan _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
