Atmospheric motions span a hierarchy of horizontal scales, from microscale turbulence up to planetary-scale waves: microscale (eddies, metres to tens of metres) < mesoscale (fronts, thunderstorms, ~1-100 km) < synoptic scale (cyclones, ~1000 km) < planetary scale (Rossby/planetary waves, ~10,000 km).
Arranging by increasing horizontal scale: (a) small eddies are the smallest (microscale), followed by (c) fronts (mesoscale), then (d) synoptic cyclones (synoptic scale), and finally...
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