Jonathan Gregory wrote:
> Dear Heinke
>
> Thanks for your email. I am not commenting here on every name, but on
> illustrative cases
>
That is no problem.
> (1)
>
>> double threshold
>> threshold:standard_name = "air_temperature_threshold" ;
>> threshold:units = "degC" ;
>>
>> frost_days_index_per_time_period ->
>> number_of_days_with_air_temperature_below_threshold
>> threshold = 0.
>> cell method = "time: minimum"
>>
>
>
>> Is this correct ?
>>
> Yes.
> The use of cell_methods in this way is an extension of current use. In fact
> I think I would refine it to be "time: minimum within days" (as suggested
> later in my last email). That makes it clearer what the minimum applies to.
>
That is much better.
>
>> Why do we need special threshold CF names ?
>> Can we use air_temperature as threshold standard name ?
>>
> It has a slightly different meaning, don't you think? "air_temperature" is
> the standard name for a quantity we measure or model, but "air_temperature_
> threshold" is a defined parameter.
>
That is o.k. for us.
>
>> air_temperature_threshold is in Kelvin not in Celsius. This should not
>> be a problem but it is a little bit confusing. What do you think ?
>>
> It could be in either degC or K, since it has a units attribute of its own.
>
o.k.
> (2)
>
>> warm_spell_days_index_wrt_90th_percentile_of_reference_period ->
>> number_of_days_with_mean_air_temperature_above_percentile_and_spell_length_above_threshold
>>
>> double percentile
>> threshold:standard_name = "percentile_function_of_air_temperature" ;
>> threshold:units = "percent" ;
>>
>> double threshold
>> threshold:standard_name = "spell_length_threshold" ;
>> threshold:units = "day" ;
>> data :
>> percentile = 90. ;
>> threshold = 6 ;
>>
>> variable attribute e.g. 1961-1990 (climate reference period)
>>
>> I would prefer the name percentile_function_of_air_temperature instead
>> of cumulative_probability_of_air_temperature.
>> What do you think ?
>>
>
> I'm not sure that's correct. I would understand "percentile function" to
> mean a function which gave a percentile, so a percentile function of air
> temperature would be a particular air temperature value. The cumulative
> probability is the independent variable i.e.
>
> 90th percentile of air temperature = percentile_function (air_temperature
> values, cumulative_probability = 90%)
>
You are right. But I am careful with the word 'probability', because
for transient climate model runs
we have different probability spaces and it mus be clear what we count.
What do you think ?
>
>> It is not the maximum. It is the mean temperature.
>>
> We can omit "mean" or "maximum" from the standard name if we put it in
> the cell_methods as "time: mean|maximum within days".
>
>
>> The name is very long.
>>
> Yes - but it is informative!
>
Thank you !
> (3)
>
>> growing_season_length_index -> growing_season_duration
>>
>> Counted are the number of days per calendar year between the first
>> occurrence of at least 6 consecutive days where the daily mean
>> temperature is above 5 degree Celsius and the first occurrence of at
>> least 6 consecutive days after 1st of July where the daily mean
>> temperature is below 5 degree Celsius.
>>
>
> This is very detailed, and I guess it is very specific and other people will
> use different definitions. I wonder whether it is really useful to have a
> standard name for a quantity with such a complicated definition involving
> many choices.
>
I think we can queue it and look what will happen in the future.
> (4)
>
>> What do you think about number_of_frost_days_with_no_snow_cover ?
>>
> Since we are not using "frost days" elsewhere, I would suggest
> number_of_days_with_air_temperature_below_threshold_and_zero_surface_snow_amount
>
> I think it is still worth considering the alternative approach for these
> quantities with one or two thresholds of simple standard names such as
> number_of_days and fraction_of_days, and rely on the coordinate variables
> alone to indicate the conditions that apply.
>
Sorry, but can you explain it. I didn't understand.
Thank you for your comments about CV. Frank has holidays and he will be
back in October.
Best wishes
Heinke
> Best wishes
>
> Jonathan
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Received on Thu Sep 13 2007 - 02:19:50 BST
