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Guidelines for subannual data resolution

The subannual column in the data format specifies the temporal scope of the timeseries data at a sub-annual resolution. The column is not required; if it is not provided, the timeseries is understood as yearly data. The default value for this column is 'Year'.

This column is an extension compared to the format as defined by the IAMC and used in the context of IPCC Reports and other model comparison studies. These previous scenario ensembles only used yearly timeseries data.

Overview

The list of subannual "timeslices" are grouped into several categories and levels of temporal detail. Timeslices can be either understood as consecutive (continuous) periods or as representative periods (e.g., "summer-day").

Each item in the codelists below includes an attribute duration indicating the duration relative to a normal year (i.e., not a leap year).

Yearly data

The default entry for the openENTRANCE data format in the "subannual" column is "Year". Its duration attribute is set to 1.

Continuous time formats with subannual resolution

Months

See months.yaml for the codelist.

Example for using this codelist

The code snippet (Python) below shows how to obtain a mapping of months to their respective duration.

import yaml

with open(f"definitions/subannual/months.yaml", "r") as stream:
    months = yaml.safe_load(stream)

mapping = dict([(m, eval(attr['duration'])) for (m, attr) in months.items()])

Daily or hourly resolution

We follow the datetime format (ISO 8601, see this overview on Wikipedia) to describe continuous-time subannual resolution.

For consistency across the many models and tools in the consortium, we use the format defined as yyyy-mm-dd hh:mmz, where z specifies the timezone in the format +hh:mm. For Python users, more details can be found in the documentation of the datetime format.

Time zone

Given the regional focus of this project, all hourly timestamps must be given in Central European (standard) time without consideration of daylight saving time (a.k.a. "summer time").

⚠️ Any hourly timestamp must include the tag z = '+01:00'.

Calendar

It is understood that continuous-time data follows the real calendar, so that 2020-01-01 (January 1, 2020) is a Wednesday. Leap years must include the data for February 29.

Time periods

It is understood that any value identified by a datetime timestamp refers to the period following that time until the next given data point, This means that if a model/scenario reports data at an hourly resolution, the value associated with the timestamp 2020-01-01 00:00+01:00 refers to the period from midnight until 1am.

Wide format vs. long format

The common openENTRANCE data format specifies that the "year" is separated from the subannual timeslice identifier (wide format). This can be implemented by specifying the "subannual" column as mm-dd hh:mmz and setting the data column headers to yyyy.

model scenario region variable unit subannual 2015 2020 2025
GENeSYS-MOD Societal Commitment Europe Primary Energy GJ/y 01-01 00:00+01:00 7.99 7.50 ...
... ... ... ... ... ... ... ... ...

Here, 7.99 GJ/yr is the amount of primary energy used in Europe in the first hour of the year 2015.

Alternatively, one can represent the data with a "time" (in datetime format) and a "value" column (long format).

model scenario region variable unit time value
GENeSYS-MOD Societal Commitment Europe Primary Energy GJ/y 2015-01-01 00:00+01:00 7.99
GENeSYS-MOD Societal Commitment Europe Primary Energy GJ/y 2020-01-01 00:00+01:00 7.50
... ... ... ... ... ... ...

A (preliminary) utility function to translate from timeseries data in datetime format (i.e., with columns 'time', 'value') to subannual + year format is available via nomenclature.swap_time_for_subannual().

Representative timeslices and other categories

Other categories to be added over time