Con la fisica tra le nuvole: cenni di termodinamica dell’atmosfera PPAAFF A.A. 2011-12 T López-Arias Parte II 23 maggio 2012 La classificazione delle nuvole Misura dell’umidità relativa: punto di rugiada e temperatura del bulbo bagnato Adiabatica secca e umida: stabilità e instabilità atmosferica Ruolo delle nuvole nella previsione Quakero di origini Lavora con suo padre nella produzione di prodotti chimici farmaceutici Con il farmacista William Allen fonda la “Askesian Society” dove per la prima volta legge il suo saggio sulle nuvole Nel 1803 scrive “Essay on the modification of clouds” dove Luke Howard (1772-1864) da la nomenclatura dei ddiivveerrssii ttiippii ddii nnuuvvoollee cchhee perdura fino ad oggi Corrisponde a lungo con Goethe che gli dedica diversi poemi Nel 1819 scrive “The weather of London” Caspar D. Friedrich (1774-1840) “Since the increased attention which has been given to Meteorology, the study of the various appearances of water suspended in the Atmosphere is become an interesting and even necessary branch of that pursuit. [...] They (the clouds) are subject to certain distinct modifications, produced by the general causes which effect all the variations of the Atmosphere: they are commonly as good visible indications of the operation of these causes as is the countenance of the state of a person’s mind or body” Neither it is pretended that “ Electricity is any further concerned in the production of rain than as a secondary agent, which modifies the effect of two grand predisposing causes- a falling temperature and the influx of vapor” LLuukkee HHoowwaarrdd,, 11880033 Cirrus, cumulus, stratus, nimbus From “On the modification of clouds”, Luke Howard, 1803 CIRRUS: Nubes cirrata, tenuissima, quae undique crescat Parallel, flexuous, or diverging fibres, extensible by increase in any or in all directions CUMULUS: Nubes cumulata, densa, sursum crescens Convex or conical heaps, increasing upward from a horizontal base STRATUS: Nubes strata, aquae modo expansa, deorsum crescens A widely extended, continuous, horizontal sheet, increasing from below upward Cirrus (Ci) Cumulus (Cu) Stratus (St) From “On the modification of clouds”, Luke Howard, 1803 Intermediate modifications: CIRRO-CUMULUS: Nubecualae densiores subrotundae et quasi in agmine appositae Small, well defined roundish masses, in close horizontal arrangement or contact CIRRO-STRATUS: Nubes extenuata subconcava vel undulata. Nubeculae hujusmodi appositae Horizontal or slightly inclined masses attenuated towards a part or the whole of their circumference, bent downward, or undulated; separate, or in groups consisting of small clouds having these characters Compound modifications: CCUUMMUULLOO--SSTTRRAATTUUSS NNuubbeess ddeennssaa,, bbaassiimm ppllaannaamm uunnddiiqquuee ssuuppeerrccrreesscceennss,, vveell ccuujjuuss mmoolleess lloonnggiinnqquuaa videtur partim plana partim cumulata The Cirro-stratus blended with the Cumulus, and either appearing intermixed with the heaps of the latter or superadding a wide-spread structure to its base CUMULO-STRATUS Nubes densa, basim planam undique supercrescens, vel cujus moles longinqua videtur partim plana partim cumulata The Cirro-stratus blended with the Cumulus, and either appearing intermixed with the heaps of the latter or superadding a wide-spread structure to its base CUMULO-CIRRO-STRATUS vel NIMBUS Nubes vel nubium congeries [superné cirrata] pluvium effundes The Rain cloud. A cloud or system of clouds from which rain is falling. It is a horizontal sheet, above which the Cirrus spreads, while the Cumulus enters it laterally and from beneath Stratocumulus (Sc) LOW CLOUDS Cumulus (Cu) Cumulonimbus (Cb) Stratocumulus (Sc) Stratus (St) Stratus (St) Cumulus (Cu) Cumulonimbus (Cb) MEDIUM CLOUDS Altostratus (As) Nimbostratus (Ns) Altocumulus (Ac) Altrostratus opacus o nimbostratus (Ns) Altocumulus (Ac) stratiformis (str) Altrostratus (As) translucidus HIGH CLOUDS Cirrus (Ci) Cirrus (Ci) Cirrostratus (Cs) Cirrocumulus (Cc) CCiirrrruuss ffiibbrraattuuss oo uunncciinnuuss Cirrostratus (Cs) Cirrocumulus (Cc) stratiformis (Cc str) Cirrocumulus (Cc) floccus (Cc flo) Cirrocumulus (Cc) lenticolaris (Cc len)