From the TU Braunschweig website:

METTOOLS is the German-speaking conference of the technical committee environmental meteorology (FA UMET) of the German Meteorological Society.

Environmental meteorology is the branch of meteorology that deals with environmental issues. In doing so, fundamental and application-related investigations on phenomena and processes in the atmospheric environment are carried out, which are conditioned by anthropogenic interventions.

Every three years, the Technical Committee for Environmental Meteorology organizes the METTOOLS symposium, where meteorological issues of environmental protection are discussed in depth.