WMO's Emergency Response Activities (ERA) programme involves the application of specialized atmospheric dispersion-modelling techniques to track and predict the spread of airborne hazardous substances in the event of an environmental emergency. This kind of specialized application depends directly on the operational infrastructure of the numerical weather prediction systems that are implemented and maintained at many of the global, regional or national meteorological centres within WMO's World Weather Watch system.

The ERA programme was established to assist National Meteorological and Hydrological Services, their respective national agencies and relevant international organizations to respond effectively to environmental emergencies involving large-scale dispersion of air-borne hazardous substances.