Principal plane

{
  "id": "MLC-T-MET-008152",
  "term": "Principal plane",
  "field": "Meteorology and atmospheric science",
  "definition": "The vertical plane passing through the observer, the zenith, and a celestial body, typically the sun. This plane contains the sun's entire vertical circle from the horizon to the zenith and down to the nadir. Many atmospheric optical phenomena, such as the subsun and portions of certain halos and arcs, are observed along or symmetric to the principal plane.",
  "synonyms": [
    "sun’s meridian",
    "sun’s vertical"
  ],
  "url": "https://mlchart.com/terminology/meteorology/principal-plane/"
}