Hi!
Based on the input I have received in this list, I have done the following for my own project. Any comments are very welcome:
A new standard name modifier: confidence, used like this:
float wind_speed_confidence(time, latitude, longitude) ;
wind_speed_confidence:units = "1" ;
wind_speed_confidence:standard_name = "wind_speed confidence" ;
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" ;
...an alternative for percentile could be cumulative_distribution_function_over_realization.
Then, there is the problem of certainty that a temperature will be within a given range. I have tried the following, using a new standard_name (interval_of_air_temperature), along with the previously mentioned confidence modifier:
float confidence_interval(confidence_interval) ;
confidence_interval:units = "K" ;
confidence_interval:standard_name = "interval_of_air_temperature" ;
confidence_interval:long_name = "air_temperature offset from a given value (in either direction)" ;
float air_temperature_confidence(time, confidence_interval, latitude, longitude) ;
air_temperature_confidence:units = "1" ;
air_temperature_confidence:standard_name = "air_temperature confidence" ;
air_temperature_confidence:long_name = "probabilty of air_temperature within +/- confidence_interval" ;
This allows for several confidence intervals.
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 I have tried to solve by adding another standard_name (limit_of_precipitation_amount):
float precipitation_limit(precipitation_limit) ;
precipitation_limit:units = "kg m2" ;
precipitation_limit:standard_name = "limit_of_precipitation_amount" ;
float precipitation_limit_confidence(time, precipitation_limit, latitude, longitude) ;
precipitation_limit_confidence:units = "1" ;
precipitation_limit_confidence:standard_name = "precipitation_amount confidence" ;
precipitation_limit_confidence:long_name = "probability of precipitation_amount above precipitation_limit" ;
When working with this, I found that expressing percentiles and probabilities as dimensions, instead of attributes, made the relationship between them more intuitive. This also made using ncview to compare various percentiles for the same variable very easy, in case you're into that sort if things..
-- Vegard
----- Original Message -----
Fra: "Vegard B?nes" <vegard.bones at met.no>
Til: cf-metadata at cgd.ucar.edu
Sendt: 15. november 2011 10:10:02
Emne: [CF-metadata] standards for probabilities
Hi!
I am trying to create a document containing various probability values for weather forecasts. But I do have some problems finding out how to express what I want to say using the cf metadata standard.
I want to express such things as "25th percentile precipitation amount" (based on ensemble data), and probability that air temperature will be within 2.5 degrees of the forecast. How should I do this?
For percentiles, may I do something like this?
float precipitation_25(time, x, y) ;
precipitation_25:standard_name = "precipitation_amount" ;
precipitation_25:long_name = "precipitation_amount 25th percentile" ;
...
Also, as far as I can tell, there is no standardized names like probability_of_x or probability_of_x_within_y. How can I express this?
-- Vegard
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Received on Tue Nov 29 2011 - 03:03:14 GMT
