The Secchi disk is a device used to measure water transparency in open waters of lakes, bays, and the ocean. A pattern is drawn or painted onto a card or acrylic, mounted on a pole or line, and lowere
d slowly in the water. The depth at which the pattern on the disk is no longer visible is taken as a measure of the transparency of the water. This measure is known as the Secchi depth and is related to water turbidity.
A special (and rare) case of the process of occlusion, where the point at which the cold front first overtakes the warm front (or quasi-stationary front) is at some distance from the apex of the wave
cyclone.
A burst of secondary charged and neutral particles arising when primary cosmic rays collide with the atmospheric oxygen or nitrogen nuclei in the upper atmosphere. The collision produces mostly pions
(π), along with some kaons (K), antiprotons, and antineutrons. Neutral pions very quickly decay, usually into two gamma rays. Charged pions also decay but after a longer time. Therefore, some of the pions may collide with yet another nucleus of the air before decaying, which would be into a muon and a neutrino. The fragments of the incoming nucleus also interact again, also producing new particles.
A burst of secondary charged and neutral particles arising when primary cosmic rays collide with the atmospheric oxygen or nitrogen nuclei in the upper atmosphere. The collision produces mostly pions
(π), along with some kaons (K), antiprotons, and antineutrons. Neutral pions very quickly decay, usually into two gamma rays. Charged pions also decay but after a longer time. Therefore, some of the pions may collide with yet another nucleus of the air before decaying, which would be into a muon and a neutrino. The fragments of the incoming nucleus also interact again, also producing new particles.
An ice crystal formed by a process other than homogeneous or heterogeneous nucleation, as by shatter of a drop freezing on accretion, or breakup of an ice particle on evaporation.