Nimbostratus cloud
Under Luke Howard's first systematized study of clouds, carried out in France in 1802, three general cloud "forms" were established based on appearance and characteristics of formation: "cirriform," "cumiliform" and "stratiform." These were further divided into upper and lower types depending on altitude. In addition to these three main types, Howard added two names to designate multiple cloud types joined together: "cumulostratus," a blending of cumulus clouds and stratus layers, and "nimbus," a complex blending of cirriform, cumuliform, and stratiform clouds with sufficient vertical development to produce significant precipitation.
Cirrus cloud
Cirrus (cloud classification symbol: Ci) is a genus of atmospheric cloud generally characterized by thin, wispy strands, giving the type its name from the Latin word "cirrus", meaning a ringlet or curling lock of hair. This cloud can form at any altitude between and above sea level. The strands of cloud sometimes appear in tufts of a distinctive form referred to by the common name of "mares' tails".