Occultation techniques for observing the Earth’s atmosphere and climate comprise solar, lunar, stellar, navigation, and satellite-crosslink occultation methods, exploiting the electromagnetic spectrum from optical to radio signals via refraction, absorption, scattering, and reflection. Retrieved atmospheric variables range from bending angle, refractivity, pressure, geopotential height, temperature, and water vapour to greenhouse gases and particulate species such as aerosols and cloud liquid water. Information on ionosphere and space weather is also provided.

Occultation methods share the unique properties of self-calibration, high-accuracy and vertical resolution, global coverage, and, if using radio signals, all-weather capability. Global Navigation Satellite System (GNSS) radio occultation has become particularly successful over the recent decades and provides accurate refraction-based measurements. Occultation data are of high utility in atmospheric physics, meteorology, and climate science. Their application has further broadened in recent years and new satellite missions and observation methods are on the way.

The OPAC-IROWG 2016 Workshop brought together members from the different sub-communities and users of occultation data. The present AMT special issue is dedicated to the results of this conference.