URCLIMInfoRequirements

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This page is dedicated to express requirements wrt geodata needed by urban climate scientists to run their models, in particular in the context of the project URCLIM. The purpose of this page is to isolate somehow the need of data from existing sources to be as technology neutral as possible. It is a wiki so that there may be discussion -on the page or through the discussion view- about the need to specify it more.

Content : morphology (physical characteristics of the surface of earth in contact with atmosphere)

  • mean building height
  • surface of walls in contact with the atmosphere (or the ratio between this quantity and the surface of the area)
  • building fraction (surface of buildings seen from above divided by the surface of the area)
  • road fractions
  • other impervious surfaces fractions
  • high vegetation fraction (can be above the other elements)
  • low vegetation fraction

Content : architectural properties

  • depth, thermal conductivity, heat capacity of each layer of wall (for example for the layer of structural material and for the insulation layer inside or outside).
  • the same for roofs
  • the same for the inner floors and walls (all packed together)
  • albedo and emissivity of walls
  • the same for roofs
  • the fraction of windows on the external facades
  • the thermal characteristics of the windows
  • the presence of shelters on windows
  • note : proxies for indicators on architectural parameters, that can be interpreted provided we have an architecture database (Principle : to define with experts in architecture, an architecture database that will describe how, in each city, buildings are typically built, depending on the following parameters)
    • building's age
    • building's use (residential, commercial, offices, ...)
    • building's type (single house detached, high-rise building, etc...)

Content : building's use and socioeconomic information

  • fraction of each use in the building (e.g. to describe complex patterns as commercial in first floor, then offices and residential appartements above)
  • information on internal charges (how much energy per square meter comes from electric apparatus, cooking and so on)
  • information on the domestic heating target temperatures (day/night)
  • type of domestic heating
  • information on the occupancy or not of the building during daytime/nighttime/holidays
  • information on air conditionning use and, if any, target temperature

Content : vegetation description

  • (for high vegetation only) height of trees
  • (for high and low vegetation) type of trees (at least coniferous/broadleaf)
  • (for high and low vegetation) quantity of leaves (m2 of leaves per m2 of soil below), depending of time in the year
  • (for high and low vegetation) soil depth (depth where roots are present)


Spatial extent, resolution, accuracy

  • Spatial extent : the cities of Helsinki, Toulouse, Bucharest, Gent, Brussels, Rotterdam, The Hague, Amsterdam, Utrecht, Paris.
  • During URCLIM, the spatial resolution of the atmospheric models with TEB will typically range between 4km and 100m. TEB has sometimes been used at finer scale, but this reaches the limits of its hypothesis of 'averaged urban canyon'. Technically, the input data should be at better resolution than the model resolution (so better than 100m). However, given the physics of the model, the spatial scale of the 'urban block' (typically the urban area containind buildings, vegetation and car parks surrounded by roads) is preferred. In general, in the city centers the urban blocks are smaller than 1ha, while they can be larger in suburban areas.

Temporal extent

Format

  • Format : The climate models process raster data. Either regular grid data (50x50m) or areal data at comparable resolution for the thematic info (for example following statistical units). Regular grid make it easier to do comparison across time

Other

  • Reproducibility : if data are available only on one city, it is relevant to mention if similar data are available on other cities of the project.
  • License : URCLIM is attached to open data -creative commons license or similar-. Whenever a dataset is not open it should be at least available for free for the scientist to use it.

Explanation associated on TEB

The Town Energy Balance (TEB) model is used to simulate the energy exchanges between the urban surface and the atmosphere. when coupled to an atmospheric model, this allows to simulate the urban microclimate (such as the urban heat island, the potential modification of rain by the city, ...), as well as some impacts of weather and climate on the city (such as energy consumption of buildings, thermal comfort, water needs by urban vegetation, ...). TEB is indeed based on an idealization of the urban morphology, where all buildings, pervious and impervious surfaces within the grid mesh are merged into an urban canyon-like feature (one road, mixed with gardens, being situated between 2 facing identical buildings). In addition to the land cover and morphological information necessary to define this canyon, TEB also requires some information on the architecture of the building (what materials and surface materials of roofs and walls, at minimum, and their thermal and radiative properties), the building's uses, the vegetation (at least low and high vegetation fractions), the inhabitants energetic behaviour.