[CF-metadata] standards for probabilities

From: Jonathan Gregory <j.m.gregory>
Date: Fri, 2 Dec 2011 10:10:20 +0000

Dear Vegard

> A dimension (and variable) for specifying percentiles:
> float percentile(percentile) ;
> percentile:units = "1" ;
> percentile:standard_name = "cumulative_distribution_function" ;
> float air_temperature_percentiles(time, percentile, latitude, longitude) ;
> air_temperature_percentiles:units = "K" ;
> air_temperature_percentiles:standard_name = "air_temperature" ;

This looks sensible to me. Are you proposing cumulative_distribution_function
as a new standard name?

> ...an alternative for percentile could be cumulative_distribution_function_over_realization.

Yes. That would be more informative, and therefore preferable, I think.

> Then, there is the problem of certainty that a temperature will be within a given range.

Could you do that like this:

float air_temperature(air_temperature);
  air_temperature:bounds="air_temperature_bounds";
  air_temperature:units="K";
float air_temperature_bounds(air_temperature,2);
float air_temperature_confidence(time,air_temperature,latitude,longitude);
  air_temperature_confidence:standard_name="probability";

Then the air_temperature_bounds specify the ranges of air temperature for
which the probability is evaluated. probability would be a new standard name
as well. Again it could be made more informative as something like
probability_over_realization. This is instead of a standard_name modifier
and seems more consistent to me with the treatment of percentile. It is a
kind of transpose.

> Also, which I did not mention in the previous emails, I also wanted to express the probability of at least x mm of precipitation.

This can be done in the same way as the probability of air temperature ranges,
with the upper bounds for precipitation ranges set high enough that they are
effectively infinite.

> When working with this, I found that expressing percentiles and probabilities as dimensions, instead of attributes, made the relationship between them more intuitive.

I agree.

Cheers

Jonathan
Received on Fri Dec 02 2011 - 03:10:20 GMT