> as lemmas

1905 A. W. Clayden Cloud Stud. i. 10 Professor Hildebrandsson, of Upsala, and the Hon. Ralph Abercromby jointly submitted a revised scheme, the main feature of which was the introduction of a new class of clouds, to be distinguished by the prefix alto- before the other name. Such alto clouds were less lofty and denser than cirrus.

1905 A. W. Clayden Cloud Stud. viii. 120 Higher clouds of the alto or cirrus kinds.

1917 A. H. Munday Eyes of Army & Navy vi. 74 The middle layer consists chiefly of the alto clouds and is to be expected at a height of from 10,000 to 25,000 feet.

1952 J. A. Steers et al. Lake's Physical Geogr. (ed. 3) i. vii. 94 In British practice the distinction between ‘alto’ and ‘cirro’ clouds lies in the fact that the first are clouds of medium height the base of which lies above 7000 but below 20,000 feet..whereas the base of the latter lies above 20,000 feet.

1990 Internat. Jrnl. Climatol. 10 580 Observed cirrus cloud frequencies varied much less than alto-level frequencies.

2004 R. Buckley et al. Weather 76 (caption) Irregular altos. These irregular altocumulus clouds are gradually thickening and may bring rain.