A street-level sensor network in support of high-resolution modelling of urban weather and climate in Bristol, UK

The topography of Bristol, located in a basin and separated from the Bristol Channel coast by hills and a narrow gorge, creates a unique climate where urban effects occur along with orographic, and coastal effects. Nocturnal cold air pooling in the city centre can compete with urban heat island effects. Bristol is also prone to flooding and air pollution episodes due to frequent inversions in the basin. To support high-resolution atmospheric modelling efforts of the interplay between urban, orographic and coastal effects, in 2024 we deployed an automatic weather station network in the Greater Bristol area. With 40 stations measuring temperature, humidity and precipitation every 5 minutes, the network covers intra-urban differences, different altitudes and varying distances from the coast within a 15 x 15 km area. Stations are installed on lampposts at 3 m height to reflect pedestrian-level urban conditions, with selected stations in parks and rural areas.

We present individual cases and average differences in air temperature and precipitation measured during the first year of operation. Urban heat islands up to 7 K were observed within the Bristol basin. On average, nights in the city centre were 2.6 K warmer in summer and 1.3 K in winter. Frost was four times more common in the rural area than in the city centre. However, for about 10% of the time we observed that higher-elevation suburban areas were warmer compared to the basin where the city centre is located. In 7% of the nights, not the city centre, but stations close to the coast were warmest. Rain gauges provided detailed data on individual storm tracks and events and revealed clear orographic effects. This unique open dataset serves multi-institutional projects to improve and test hectometric urban weather predictions, air pollution dispersion, flooding, and thermal comfort modelling.