objective analysis
objective forecast
oblique visibility
observation
observational network
occluded depression
occluded front
occlusion
ocean station vessel
ocean weather station
oceanic meteorology
oceanicity
oceanity
octant
offshore wind
okta
ombrometer
omega equation
onshore wind
opacus (op)
opalescence
open cells
open-scale barograph
operational numerical model
optical air mass
optical density of a cloud
optical depth
optical phenomenon
optical probing of the atmosphere
optical refractive index
optical thickness
optimum interpolation
ordinary agricultural meteorological station
ordinary agrometeorological station
ordinary climatological station
ordinary radiation station
orographic
orographic cloud
orographic depression
orographic isobar
orographic occlusion
orographic precipitation
orographic vortex
orographic wind flow
osmometer
outbreak of air
outgoing radiation (long-wave)
overcast sky
overlapping averages
overshooting tops
oxygen band
oxygen-ozone system
ozone
ozone layer
ozone shield
ozone sonde
ozone spectrophotometer
ozonometer
ozonosphere