| NATS 101 Lecture 11 Clouds |
| Summary: Condensation |
| Condensation | |
| Occurs by cooling or moistening of air | |
| CCN permit condensation at RH near 100% | |
| Small (<0.2 to ~1 microns) airborne particles | |
| Responsible for haze formation when RH < 100% |
| Summary: Fog |
| Fog - a cloud at the ground | |
| Composed of small (~20 micron) water drops | |
| Four primary types of Fog | |
| Radiation-Advection-Upslope-Steam | |
| Occur under distinct weather conditions |
| Cloud Types |
| Excluding fog, virtually all clouds form when air rises, expands and cools to below its dew point | |
| Despite having a similar formation mechanism, a diverse range of cloud types exists! |
| Cloud Classification |
| A morphological classification scheme developed by Luke Howard (1803) | |
| Latin words used to describe different cloud types as they appear to observer on the ground | |
| Four basic cloud types and combinations | |
| stratus - sheet-like clouds (layer) | |
| cumulus - puffy clouds (heap) | |
| cirrus - wispy clouds (curl of hair) | |
| nimbus - rain clouds (violent rain) |
| Cloud Classification |
| Height grouping modification of Howard scheme (Abercromby and Hildebrandsson, 1887) | |
| Still used today | |
| Ten principle cloud forms | |
| High - Middle - Low - Vertical Development |
| Slide 7 |
| Cloud Classification |
| Other cloud types | |
| Lenticular - stacks like saucers above and downwind of mountains (lens-shaped) | |
| Banner - cloud at top and immediately downwind of mountain peaks | |
| Mammatus - pendulous undulations that occur underneath some thunderstorm anvils (breast) | |
| Pileus - cloud situated just above the top of a thunderstorm top (hat) |
| Cloud Classification |
| Other cloud types | |
| Kelvin-Helmholtz - billowed clouds that resemble breaking waves and form in strong wind shear | |
| Nacreous - thin, sometimes iridescent clouds in stratosphere (30 km height) (mother of pearl) | |
| Noctilucent - thin clouds in upper mesosphere (80 km height), seen in polar twilight (night-light) |
| Cirrus (Ci) |
| Cirrocumulus (Cc) |
| Cirrostratus (Cs) |
| Altocumulus (Ac) |
| Altostratus (As) |
| Nimbostatus (Ns) |
| Stratus (St) |
| Stratocumulus (Sc) |
| Cumulus (Cu) Humilis |
| Cumulus Congestus (Cu) |
| Cumulonimbus (Cb) |
| Supercell Cb |
| Mammatus |
| Pileus |
| Lenticular |
| Lenticular with Rotor |
| Banner Cloud |
| Kelvin-Helmholtz |
| Jet Contrail |
| Summary: Cloud Classification |
| Next Assignments |
| Next Lecture: | |
| Topic - Vertical Stability | |
| Reading - Ahrens p 112-120 | |
| Problems - 5.1, 2, 3, 4, 5, 7 | |