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 B?rring
FDr, Forskare
PhD, Research Scientist
SMHI / Swedish Meteorological and Hydrological Institute
Rossby Centre
SE - 601 76 NORRK?PING
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
Bes?ksadress / Visiting address: Folkborgsv?gen 17
Received on Fri Mar 24 2017 - 02:10:08 GMT
