The most difficult at­mo­spher­ic phe­nom­e­na riddles

Sprites are large-scale electrical discharges that occur high ( 50–90 km) above cumulonimbus, giving rise to a quite varied range of visual shapes flickering in the night sky. They are usually triggered by the discharges of positive lightning between an underlying thundercloud and the ground. Sprites have been blamed for otherwise unexplained accidents involving high altitude vehicular operations above thunderstorms. Since their 1989 discovery, sprites have been imaged from the ground, from aircraft and from space, and have become the subject of intensive investigations.

St. Elmo's fire is a form of plasma. The electric field around the object in question causes ionization of the air molecules, producing a faint glow easily visible in low-light conditions. Conditions that can generate St. Elmo's fire are present during thunderstorms, when high voltage differentials are present between clouds and the ground underneath. The nitrogen and oxygen in the Earth's atmosphere cause St. Elmo's fire to fluoresce with blue or violet light; this is similar to the mechanism that causes neon lights to glow

The Saharan Air Layer (SAL) is an extremely hot, dry and sometimes dust-laden layer of the atmosphere that often overlies the cooler, more-humid surface air of the Atlantic Ocean. The SAL passes over the Canary Islands where the phenomenon is named "Calima" and manifests as a fog that reduces visibility and deposits a layer of dust over everything.