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A throughout description of the database can be found in:

Di Napoli C, Barnard C, Prudhomme C, Cloke HL and Pappenberger F (

2020

2021) ERA5-HEAT: A global gridded historical dataset of human thermal comfort indices from climate reanalysis. Geoscience Data Journal

,

8: 2–10. https://

rmets.onlinelibrary.wiley.com/doi/full/

doi.org/10.1002/gdj3.102



Thermal comfort indices descriptions

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Mean radiant temperature (MRT): The MRT is the uniform temperature of a fictive black-body radiation enclosure which would result in the same net radiation energy exchange with a human subject as the actual, more complex radiation environment (Figure 1). The MRT is an international standard for thermal environment ergonomics according to the International Organization for Standardization.[2] It also a standard for thermal environmental conditions for human occupancy according to the American Society of Heating, Refrigerating and Air-Conditioning Engineers.[3]

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Figure 1 Graphical explanation of the mean radiant temperature (MRT). Adapted from [4].

 

Summary variable table


Variable

Description

UNIT

Mean radiant temperature

Numerical representation of how human beings experience radiation. It applies to a human subject placed in an outdoor environment and irradiated by solar and thermal radiation both directly and diffusely.

K

Universal thermal climate index

Numerical representation of the thermal comfort/discomfort perceived by a human subject when exposed to outdoor conditions. It is based on a state-of-the-art model that simulates human body’s physiological responses to air temperature, humidity, wind speed and radiation.

K


Thermal comfort indices algorithm

The dataset is computed via a sequence of well-defined, computer-automated steps (algorithm, Figure 2). The algorithm takes as input the following ERA5 reanalysis atmospheric variables: air temperature and relative humidity (from dew point temperature) at 2 meters above the ground, wind speed at 10 meters above ground level and radiation fluxes at the Earth’s surface. Radiation fluxes - both solar and thermal - are used to calculate the MRT by taking into account the time period in which modelled radiation is accumulated and the Sun’s position changes.[5] The MRT, air temperature, relative humidity and wind speed are input into a multi-variable equation which has the UTCI as a result.[6] The outputs of the algorithm (products) are hourly reanalysis data of MRT and UTCI at the global scale (except Antarctica).


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Figure 2 Workflow of the thermal comfort indices algorithm.

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File names are as follows:

PRODUCER_VARIABLE_DATE_Version_Dataset.nc

where:

  1. Producer: ECMWF
  2. Variable: UTCI or MRT
  3. Date: Date of the reanalysis
  4. Version: Version of the reanalysis
  5. Dataset:
    1. con: Consolidated ERA5 Data
    2. int: Intermediate ERA5 Data (ERA5T)

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