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Precipitation - Cities and FUAs

<p align="justify">This dataset provides indicators of total precipitation and extreme precipitation days in Functional Urban Areas (FUAs) and cities.</p>

<h3>Data sources and methodology</h3> <p align="justify">The indicators use <a href="https://developers.google.com/earth-engine/datasets/catalog/ECMWF_ERA5_LAND_DAILY_AGGR">ERA5-Land</a> data. Total precipitation is the sum of all liquid and frozen water—such as rain and snow—that reaches the Earth's surface each year. It excludes fog, dew, and any precipitation that evaporates before reaching the ground. Extreme precipitation days are defined as days with more than 20 mm of total precipitation. ERA5-Land is used as it provides harmonised, globally consistent coverage at fine spatial resolution (0.1 degree), enabling the production of comparable subnational indicators also where national meteorological data are not available at the required scale. </p>

<p align="justify"> These estimates may differ from official subnational climate statistics due to differences in methodological approaches, such as the use of reanalysis based top down modelling versus in situ observations, along with variations in input data sources, spatial resolution, and the models and algorithms used to generate temperature estimates. </p>

<h3>Defining FUAs and cities</h3> <p align="justify">The OECD, in cooperation with the EU, has developed a harmonised <a href="https://www.oecd.org/en/data/datasets/oecd-definition-of-cities-and-functional-urban-areas.html">definition of functional urban areas</a> (FUAs) to capture the economic and functional reach of cities based on daily commuting patterns <a href=https://doi.org/10.1787/9789264174108-en>(OECD, 2012)</a>. FUAs consist of: <ol> <li><b>A city</b> – defined by urban centres in the degree of urbanisation, adapted to the closest local administrative units to define a city.</li> <li><b>A commuting zone</b> – including all local areas where at least 15% of employed residents work in the city.</li> </ol> The delineation process includes: <ul> <li>Assigning municipalities surrounded by a single FUA to that FUA.</li> <li>Excluding non-contiguous municipalities.</li> </ul>

The correspondence table between SAUs and FUAs/cities is available in <a href=https://webfs-cfe.oecd.org/files/.Stat/cities_local_areas/fua_cities_sau_mapping.parquet>parquet </a> and <a href=https://webfs-cfe.oecd.org/files/.Stat/cities_local_areas/fua_cities_sau_mapping.csv>csv</a> format.

The definition identifies 1 272 FUAs and 1 269 cities in all OECD member countries except Costa Rica and three accession countries.</p> <h3>Cite this dataset</h3> <p>OECD Regions, cities and local areas database (<a href="http://data-explorer.oecd.org/s/1d6">Precipitations - FUAs</a>), <a href=http://oe.cd/geostats>http://oe.cd/geostats</a></p>

<h3>Further information</h3> <ul> <li> <a href=https://localdataportal.oecd.org/>OECD Local Data Portal </a> </li> <li> <a href=https://www.oecd.org/en/publications/oecd-regions-and-cities-at-a-glance-2024_f42db3bf-en.html/>OECD Regions and Cities at a Glance </a> </li> </ul> <p align="justify">For questions and/or comments, please email <a href="mailto:CitiesStat@oecd.org">CitiesStat@oecd.org</a>