Cooling or heating?

ByMaki Pa

Heating degree day (HDD) index is a weather-based technical index designed to describe the need for heating in buildings. Cooling degree day (CDD) index is an index describing the need for the cooling (air-conditioning) requirements in buildings.

HDD and CDD are derived from meteorological observations of air temperature, interpolated to regular grids at 25 km resolution for Europe. Calculated gridded HDD and CDD are aggregated and subsequently presented on NUTS-2 level, for 2017 and 2018 also on NUTS-3 level.

This dataset includes monthly data as published by the Joint Research Centre’s AGRI4CAST Resources Portal. Note that Eurostat is not the producer of the monthly data but is only re-publishing it. Annual data is calculated as the sum of monthly data by Eurostat.

The calculation of HDD relies on the base temperature, defined as the lowest daily mean air temperature not leading to indoor heating. The value of the base temperature depends in principle on several factors associated with the building and the surrounding environment. By using a general climatological approach, the base temperature is set to a constant value of 18°C in the HDD calculation. Only days with a daily mean air temperature equal to or below 15°C are considered for this calculation, so:

if mean terp day i <= 15°C then HDD day i = ( 18°C-mean temp day i ) else HDD=0

HDD month i = sum ( HDD day i to n )

By analogy for CDD are calculated for the base temperature 21°C and summed the only days with a daily mean air temperature equal or above 24°C.

Examples: If the daily mean air temperature is 12°C, for that day the value of the HDD index is 6 (18°C-12°C). If the daily mean air temperature is 16°C, for that day the HDD index is 0. If the daily mean air temperature is 26°C, for that day the value of the CDD index is 5 (26°C-21°C). If the daily mean air temperature is 22°C, for that day the CDD index is 0.

These calculations are executed daily, added up to a calendar month and subsequently to calendar years. Statistical unit is gridded meteorological data from temperature measuring stations. The HDD and CDD estimates for the EU are based on observations from about 3000 weather stations across Europe. Data are available since January 1975, but for Cyprus since January 1978.

see more at: https://ec.europa.eu/eurostat/cache/metadata/en/nrg_chdd_esms.htm

Data analysis

You can request data by Eurostat’s API like this

import pandasdmx as sdmx
import pandas as pd
estat = sdmx.Request('ESTAT', timeout=100)
exr_msg = estat.dataflow('nrg_chddr2_m')
exr_msg.response.url

and then data structure

ds_metadata = estat.datastructure('DSD_nrg_chddr2_m')
ds_metadata.codelist
for cl in ['CL_FREQ', 'CL_INDIC_NRG', 'CL_OBS_FLAG', 'CL_OBS_STATUS', 'CL_UNIT']:
    print(sdmx.to_pandas(ds_metadata.codelist[cl]))

and finally, dataset

exch_data = estat.data('nrg_chddr2_m', 
                       key={'GEO': ['FI','SE'],
                           # 'FREQ': 'M',
                            'INDIC_NRG': 'HDD'
                           },
                       params={'startPeriod': '2000-01-01'} )
data = exch_data.to_pandas()
data.to_excel('dfx_data_fi_from_2000.xlsx')

Now, you can think how to show whether climate is warming up or cooling .. or stay stable. Do we need more heating or more cooling in our houses, especially in Finland and Sweden? What do you think?

Finland + Sweden HDD from 1980, data=Eurostat

Please in reading for all of you. All ideas welcomed in comments.

Dataset: NRG_CHDDR2_M

https://ec.europa.eu/eurostat/cache/metadata/en/nrg_chdd_esms.htm, https://agri4cast.jrc.ec.europa.eu/DataPortal/Resource_Files/PDF_Documents/10.pdf

Data description

Monthly Heating and Cooling Degree Days in the European Union are collected as a time series, which starts in 1979 until last year completed. The year 1978 contains the long-term average that covers the period 1991 to the last year completed.

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