Spherical harmonics
From Glossary of Meteorology
spherical harmonics
In analogy to harmonic functions in the plane, the solutions of the Laplace equation in spherical coordinates.
Spherical surface harmonics are special sets taken over the surface of a sphere; therefore, the harmonic components are restricted to an integral number of waves over the sphere. Spherical harmonics have been applied in the study of the large-scale oscillations of the atmosphere.