Wonderful clouds (en)

Wonderful clouds

Altocumulus clouds are part of Middle Cloud group from 2000 to 7000 m up. They usually form in groups and are about 1 km thick. They contain water drops and rarely ice crystals. They don’t predict rain, unless there is a warm humid morning.

Altocumulus Cloud from the ISS

Arcus cloud is a low, horizontal cloud formation. The two types of these clouds are Roll Clouds and Shelf Clouds. A shelf cloud is associated with a leading edge of thunderstorm outflow, while roll clouds are formed by outflows of cold air from sea breezes or cold fronts in the absence of thunderstorms.

Arcus Layers with Thunderstorm

Roll Cloud in Queensland, Australia

Roll Clouds - morning glories in Queensland, Australia

Roll Cloud in Punta del Este, Uruguay

Shelf Cloud in Cape Cod

Shelf Cloud in North Dakota

Shelf Cloud in Wagga Wagga, Australia

Undulatus asperatus, from the class of Altocumulus, it was proposed as a separate cloud classification in 2009. These clouds are most closely related to undulatus clouds. They appear dark and storm-like and tend to dissipate without a storm forming.

Asperatus formation

Asperatus in Perthshire, Scotland

Cirrocumulus clouds appear white or light gray in color, forming when water vapor undergoes deposition at altitudes above 5000 m in temperate regions and above 6100 in tropical regions. With a range in thickness from 100m to 8000m. These clouds arrive in advance of the frontal system or tropical cyclone, and they indicate that the weather conditions may soon deteriorate. While they indicate the arrival of precipitations, cirrus clouds produce only fall streaks ( falling ice crystals that evaporate before  landing on the ground).

Cirrostratus nebulosus is a type of cirrostratus cloud ( the other type being cirrostratus fibratus). They are formed by gently rising air. The cloud is hard to see unless the sun shines through it at the correct angle, forming a halo.

Cirrostratus nebulosus

Cirrostratus fibratus in Sao Paolo, Brazil

Lenticular Clouds are stationary lens-shaped clouds that form at high altitudes, normally in perpendicular alignment to the wind direction. They are separated into altocumulus standing lenticularis (ACSL), stratocumulus standing lenticularis (SCSL) and cirrocumulus standing lenticularis (CCSL).

Lenticular UFO

Lenticular Arcs

Lenticular Cloud over Mt. Fuji

Lenticular Ribbon

Kelvin-Helmholts instability is occurring when there is velocity shear in a single continuous fluid or where there is a velocity difference across the interface between two fluids. As an example : wind blowing over water – the instability manifests in waves on the water surface.

Mammatus clouds ( mammatocumulus) describes a cellular patterns of pouches hanging underneath the base of a cloud. They are often associated with the anvil cloud and severe thunderstorms. They extend from the base of a cumulonimbus,  fand can also be found under altocumulus, altostratus, stratocumulus and cirrus clouds.

Mammatus with storm

The fallstreak hole or hole punch cloud/ skypunch / canal cloud or cloud hole, is a large circular or elliptical gap that appears in cirrocumulus or altocumulus clouds. This phenomenon appears when the water temperature in the clouds if below freezing, but the water has not frozen yet due to the lack of ice nucleation particles.

Polar stratospheric clouds also known as nacreous clouds, are clouds in the winter polar stratosphere at altitudes of 15000 to 25000 m. They are implicated in the formation of ozone holes due to their  content of nitric acid and/or sulfuric acid.

Cloud iridescence is the occurrence of colors in a cloud similar to those seen in oil films. An uncommon phenomenon caused by small water droplets or small ice crystals scattering light. They can be most often observed in altocumulus and lenticular clouds.

Noctilucent clouds ( night clouds) are tenuous cloud-like phenomena, commonly observed when the Sun is below the horizon. They are the highest clouds in the Earth’s atmosphere, located in the mesosphere at altitudes of around 76 to 85 kilometers.

Noctilucent clouds over tibetan plateau

A pileus cloud, also called scarf cloud or cap cloud is a small horizontal altostratus the can appear above a cumulus or cumulonimbus cloud, appearing like a hood. Pilei tend to change shape rapidly. They are formed by strong updraft at lower altitudes, acting upon moist air above, causing the air to cool to its dew point.

Wall clouds is a large, localized and persistent lowering cloud formation that develops beneath the base of a cumulonimbus cloud that often forms tornadoes . The wall clouds are formed by a process known as entrainment, when an inflow of warm, moist air rises and converges rain-cooled air from the normally downwind downdraft. As the warm air continues to entrain the cooler air, the air temperature drops and the dew point increases, the air becoming more saturated with moisture, resulting in additional clouds in the form of a wall cloud.

The vortex cloud occurs in many natural situations like tornadoes, hurricanes and cyclones. In the photo below NASA made this phenomenon observable with the use of colored smoke.