Megacities: a new focus for weather and climate services
The growing need for weather, climate and environmental services targeted to megacities has been highlighted as an area for attention during the 16th WMO Congress.
“Seventy percent of the world’s population will be living in urban areas by 2050,” said Mr Michel Béland, President of the WMO Technical Commission for Atmospheric Sciences, during a side event on 25 May about megacities. “That will have a great impact on the types of services we provide to cities. What will be needed is quite different from a typical present-day forecast.”
Concentrated transport, heating, industry and the densely constructed environment lead to specific weather and climate patterns, as does the geographic particularities of urban areas, which are often located in coastal areas,. Examples of local patterns include anomalous heat fluxes, small-scale turbulent flows, chemical weather and contrasting albedoes.
Among the multidisciplinary threats that arise are wind storms, poor air quality, flooding, traffic impacts, and amplified impact of sea level rise and storm surges.
“Many of the world’s megacities are already experiencing air well beyond the quality guidelines recommended by the World Health Organization,” noted Liisa Jalkanen, manager of the GAW Urban Research Meteorology and Environment (GURME) project. WMO is conducting modelling, capacity building through workshops and training and pilot projects that focus on air quality forecasting,. GURME pilot projects have recently enhanced capabilities to better deal with these issues in Shanghai, Latin America and India.
A model for megacities
The Shanghai Multi-hazard Early Warning System was singled out as a prototype for addressing weather, climate and environmental issues in megacities. The initiative, developed jointly with WMO through GURME, the Shanghai Meteorological Bureau (SMB) of CMA, and the Shanghai People’s Municipal Government, includes a health-meteorology forecasting service, and cooperation at the municipal level with many government departments. “Our experience shows that we need a better understanding of atmospheric physics and chemistry, including the effects of “urban ovens” and “urban chimneys”; referring to sources of excessive heat and air pollution. We need new types of measurements and forecasts; and we need multidisciplinary teams,” said Tang Xu, Director-General of SMB.
Alexander Baklanov of the Danish Meteorological Institute shared results of the European Union MEGAPOLI project (Megacities: Emissions, Impact on Air Quality and Climate, and Improved Tools for Mitigation and Assessment), which focuses on the multiple spatial and temporal scales from street to global levels and vice versa. “Megacities, air quality and climate have complex effects on each other,” he noted. “Cities see a local, meso-scale impact of greenhouse gas emissions and urban heat islands on climate. At a regional level, the impact is still unclear.”
A new initiative proposed by the Technical Commission for Atmospheric Sciences, through the Global Atmosphere Watch (GAW) and the World Weather Research Programme (WWRP) will mobilize some, but not all, of the research to address the unique and growing needs related to urban areas and megacities, Mr Béland added.
WMO is also developing a report on megacities with the International Global Atmospheric Chemistry Project (IGAC), to be issued later this year.
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