in atmospheric chemistry
https://doi.org/10.1351/goldbook.N04143
An amorphous, dark grey, rainy cloud layer reaching almost to the ground; 300600 m vertical velocities of 0.050.2 m s1.
Source:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2180 [Terms] [Paper]