The World Meteorological Organization (WMO) is an intergovernmental organization with a membership of 193 member states and territories. It originates from the International Meteorological Organization (IMO), whose roots were laid at the International Meteorological Congress in Vienna in 1873. WMO, established by the ratification of the WMO Convention on March 23, 1950, became the UN's specialized agency for meteorology (weather and climate) a year later. operational hydrology and related geophysical sciences. The Secretariat, based in Geneva, is headed by the Secretary General. Its highest body is the World Meteorological Congress.