[CF-metadata] Request for new standard names for climatological statistics based on thresholds

Hollis, Dan dan.hollis at metoffice.gov.uk
Mon Mar 27 05:06:13 MDT 2017


Hi Lars,

I raised a very similar question a couple of years ago:
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057605.html

The outcome was inconclusive. One suggestion was to add a Boolean attribute that indicated whether the threshold value was included or not. Others thought that adding more standard names was the way to go, while others thought that a single name was sufficient.

I encourage you to read through the rest of the thread and see if it helps with your current request:
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/thread.html#57605

For info, we continue to use the existing standard names even though they do not strictly match the definitions of our 'days of rain' statistics.

Regards,

Dan


Dan Hollis   Climatologist
Met Office   Hadley Centre   FitzRoy Road   Exeter   Devon   EX1 3PB   United Kingdom
Tel: +44 (0)1392 884535   Mob: +44 (0)7342058682   Fax: +44 (0)1392 885681
E-mail: dan.hollis at metoffice.gov.uk   Website: http://www.metoffice.gov.uk
For UK climate and past weather information, visit http://www.metoffice.gov.uk/climate


-----Original Message-----
From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Bärring Lars
Sent: 24 March 2017 08:10
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] Request for new standard names for climatological statistics based on thresholds

Dear all,
 
Several standard names oriented towards climate indices for various impacts are based on thresholds, and the standard name includes the construct "..._above_threshold" or "..._below_threshold".  However, several well-established climate indices use non-strict inequalities in their definition. 
 
For model output using floating point precision the difference between using a strict and a non-strict inequality is small or even negligible, but for observational data discretized to some limited precision (typically one or no decimal digit) this makes a difference. 
 
At a workshop last week people involved in WMO/CCl Expert Team on Sector-specific Climate Indices (ET-SCI) and the joint CCl/WCRP/JCOMM Expert Team on Climate Change Detection and Indices (ETCCDI), as well as the European ECA&D programme and several research projects discussed this. 
 
The outcome of these discussions is to suggest new standard names similar to the existing ones but using the contructs "..._at_or_above_threshold" and "..._at_or_below_threshold". In all other respects these new standard names should be patterned after the following existing ones:
 
number_of_days_with_air_temperature_above_threshold
number_of_days_with_air_temperature_below_threshold
number_of_days_with_lwe_thickness_of_precipitation_amount_above_threshold
number_of_days_with_surface_temperature_below_threshold
number_of_days_with_wind_speed_above_threshold
spell_length_of_days_with_air_temperature_above_threshold
spell_length_of_days_with_air_temperature_below_threshold
spell_length_of_days_with_lwe_thickness_of_precipitation_amount_above_threshold
spell_length_of_days_with_lwe_thickness_of_precipitation_amount_below_threshold
 
The specific use cases for these extension are several ET-SCI defined indices that involves non-strict inequalities. 
 
The alternative of changing the ET-SCI definitions to use a strict inequality is not an option because they have been painstakingly defined in collaboration with user communities and/or are directly related to well-established operational usage. 
 
Likewise, to just adjust the threshold in order to turn the non-strict inequality to a strict equality (say from 30 C to 29.9 C or 29.99 C or ...) is not attractive and prone to cause confusion.
 
Kind regards,
Lars

--
Lars Bärring

FDr, Forskare
PhD, Research Scientist

SMHI  /  Swedish Meteorological and Hydrological Institute Rossby Centre SE - 601 76 NORRKÖPING http://www.smhi.se

E-post / Email: lars.barring at smhi.se
Tel / Phone: +46 (0)11 495 8604
Fax: +46 (0)11 495 8001
Besöksadress / Visiting address: Folkborgsvägen 17


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