Summer in the City: weather forecasts for the city in the making

Published on
February 4, 2013

The United Nations (UN) expect migration from rural areas to cities to continue in this century too. That means more and more people will be confronted with urban climatic conditions, which could have less-than-favourable effects on health. An e-Science project awarded last week to the Department of Meteorology and Air Quality of Wageningen University will develop and validate weather forecasts specifically for urban environments.

Much has been written about the ‘urban heat island effect’; that is, the tendency of human activities and dense buildings to make cities substantially warmer than their surroundings. Elderly people and those with health problems are especially likely to suffer from city heat. The heat wave that struck Europe in 2003, for example, led to some 70,000 extra deaths. The urban heat island effect is evident in the Netherlands as well. This was demonstrated by Wageningen University using street-level measurements done via specially fitted bicycles and observations of local weather enthusiasts. Yet, the effects of urban heat go beyond the physical discomfort of high temperatures. For one thing, labour productivity drops in cities during extremely warm periods, in relation to surrounding areas.

"The Summer in the City project aims to develop modelling tools that policymakers and urban planners can use to improve the climate in cities", says Bert Holtslag, professor of Meteorology at Wageningen University. "Beyond that, we want to develop a forecasting system to give businesses and residents very direct access to detailed, hour-by-hour information about the weather and forecasts for their city."

Huge technical challenges are involved in weather forecasting at the city level. Local urban conditions are highly variable, and physical factors (such as roads and buildings) influence the weather, which itself is infinitely variable. Extremely large datasets have to be used that include geo-information (on, for instance, buildings, roads and parks). The detailed simulations that have to be run in time and space are another extremely challenging aspect from a scientific perspective.

Results of the project will be made widely available, says Bert Holtslag. "We will not only publish the findings in scientific outlets, but also spread them via websites and social media. We want to reach the general public, because this is really new: weather forecasts specifically targeted for the working and living conditions in the city."

By analysing street-level measurements and observations, Wageningen University demonstrated the urban heat island effect in the Netherlands too.