Task: Class Definition Understanding (ontology: Earth_Environment/SWEET)

Which of the following definitions best describes 'mesoscale convective system'?

A. A cloud system that occurs in connection with an ensemble of thunderstorms and produces a contiguous precipitation area on the order of 100 km or more in horizontal scale in at least one direction. An MCS exhibits deep, moist convective overturning contiguous with or embedded within a mesoscale vertical circulation that is at least partially driven by the convective overturning.
B. A storm characterized by a fall of freezing liquid precipitation. The attendant formation of glaze on terrestrial objects creates many hazards.
C. Any disturbed state of the atmosphere, especially as affecting the earth's surface, implying inclement and possibly destructive weather.
D. A subset of mesoscale convective systems (MCS) that exhibit a large, circular (as observed by satellite), long-lived, cold cloud shield. Alternatively, a dynamical definition of an MCC requires that the system have a Rossby number of order 1 and exhibit a horizontal scale comparable to the Rossby radius of deformation. In midlatitude MCS environments, the Rossby radius of deformation is about 300 km.

Answer: A cloud system that occurs in connection with an ensemble of thunderstorms and produces a contiguous precipitation area on the order of 100 km or more in horizontal scale in at least one direction. An MCS exhibits deep, moist convective overturning contiguous with or embedded within a mesoscale vertical circulation that is at least partially driven by the convective overturning.