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

Bärring Lars Lars.Barring at smhi.se
Fri Mar 24 02:10:08 MDT 2017


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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