Dear Lars
> integral_of_air_temperature_excess_wrt_time
> "integral_of_Y_wrt_X" means int Y dX. The data variable should have an axis for X specifying the limits of the integral as bounds. "wrt" means with respect to. Air temperature is the bulk temperature of the air, not the surface (skin) temperature. The air temperature excess is the air temperature minus the air temperature threshold, where only positive values are included in the integral. Its integral with respect to time is often called after its units of "degree-days".
>
> And the corresponding change to the explanation of the standard_name integral_of_air_temperature_deficit_wrt_time
>
> Furthermore, recalling your response to my recent question (http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2016/058800.html) I suggest that a sentence elaborating on the temperature threshold should be included. You wrote
> "The data variable of the integral should have a scalar coordinate variable or a size-one coordinate variable with the standard name of air_temperature_threshold, to indicate the threshold."
I think these changes would all be fine.
> why does it have to be a scalar or size-one coordinate variable? If we consider the practical example of heating degree-days the threshold may not be the same over a large region (as is the case for Europe), in which case one would like to have a two-dimensional threshold variable.
That is an interesting question. We're regarding it as a coordinate i.e. it's
an independent variable on which the data depends. Coordinate variables are
one-dimensional. The situation you're thinking of is analogous to, for example,
temperature at the tropopause. Unlike the surfaces of 10 km altitude, or
200 hPa pressure, "tropopause" can't be defined with a single-valued numeric
coordinate, so for that reason we include the name of this surface in the
standard name of the quantity e.g. tropopause_air_temperature. If you have
a geographically varying air temperature threshold, is there a constant
definition which is being applied to obtain it?
Best wishes
Jonathan
Received on Mon May 23 2016 - 07:52:47 BST
