A 300-year history of understanding and classifying clouds, from a German language perspective

Abstract

Otto von Guericke was the first who experimentally demonstrated cloud formation by expanding and cooling of compressed air before 1663. Scientists initially grappled with the very question of why clouds float. Early explanations were hampered by limited theory, imprecise instruments, and gaps in meteorological knowledge. First attempts for distinguishing various cloud types arose towards the end of the 18th century. A key turning point came in 1803 when Howard proposed a first systematic scheme using Latin terminology for different cloud types. This effort laid the cornerstone for what would evolve into today's internationally recognized cloud classification system. The path to accurate understanding was long and iterative; early laboratory work and imprecise instruments produced repeated misjudgements that endured for decades. Manned balloon ascents provided direct measurements of meteorological parameters in the free atmosphere and in clouds, but more reliable and bias-free instruments and advances in theory were necessary to achieve reliable results. Additional techniques had to be developed to determine cloud altitudes and track their motion, gaining knowledge of vertical temperature and moisture profiles that shape different cloud types. Beginning in the 1890s, large-scale movements in the upper atmosphere were recognised by coordinated international observations. Contemporary early cloud atlases were published despite the limitations of low-contrast, poor photographs. Alternatives, like paintings or cloud watercolours, were even used to overcome these early hurdles. Coordinated observations using daily pilot balloons, kites, and later weather aircraft allowed researchers to further explain cloud formation both in stable and unstable atmospheric conditions. In addition, stratospheric and mesospheric clouds were discovered. After many efforts to publish international and national cloud atlases the World Meteorological Organization's founding in 1951 enabled the first modern International Cloud Atlas in 1956, standardising cloud observation practices and nomenclature.