Observation is fundamental to understanding global change. Atmospheric change impacts marine ecosystems, and the atmosphere is influenced by ocean physical and biogeochemical processes. Many impacts/feedbacks are focussed in the Tropics. TENATSO will support pre-operational atmosphere and ocean observation capability in the tropical Eastern North Atlantic Ocean, specifically at Cape Verde (17°36’N, 24°16’W). The entire region is data poor but plays a key role in air-sea interaction. Cape Verde is ideally located for both atmosphere and ocean observation. Being downwind of the Mauritanian up welling, the Observatory will provide unique information linking biological productivity and atmospheric composition. The location is critical for climate and greenhouse gas studies and for investigating dust impacts on marine ecosystems. The Observatory can contribute data for assessment of major marine biological resources. This Action proposes no research or monitoring: rather it supports transfer of European technology/ expertise to a developing country with strong ties to Europe. The Action is leveraged on financial support by the Partners and the Observatory is of use to European programmes. The atmospheric site will measure meteorological parameters, greenhouse and short-lived gases, and aerosols. Data links to the Global Atmospheric Watch of the WMO will be established. The ocean site will include a mooring for temperature, salinity, current and oxygen measurements and establish data links to international observing programmes. Cape Verde’s vessel will be equipped to collect samples for marine parameters. The data will contribute to GEOSS. The co-location of atmospheric and ocean Observatories is unique. The Observatory will support additional research measurements by international investigators and become a resource to European and international projects.