The Earth Story

Cumulonimbus Incus

A cumulonimbus incus is a subspecies of a cumulonimbus cloud, a vertical cloud formed when water vapor is carried by powerful upward air currents and associated with atmospheric instability and thunderstorms. In Latin the word literally means 'heaps of rain'. Cumulonimbus clouds can evolve into a variety of other (often spectacular-looking) clouds such as mammatus, pannus, pileus, venum or tuba clouds.

A mature Cumulonimbus incus (heaps of rain with an anvil shaped top) has reached the boundary between the troposphere and the stratosphere (at approximately 9km height), the tropopause. Here air ceases to cool with height and becomes utterly dry. Because of this abrupt change the cloud flattens and takes on an anvil shape. Remarkably, in equatorial regions the tropopause lies at a much higher altitude of 18km, so these clouds must similarly go higher in tropical areas.

It should not be surprising that the Cumulonimbus incus can produce dangerous atmospheric disturbances such as hail, heavy rain, strong winds, lightning and in some cases tornadoes.

If the correct atmospheric conditions are met these giants can eventually turn into supercells.

See here for a timelapse video of how these clouds are formed (and disappear):https://www.youtube.com/watch?v=C3Ny9lddzUk%2F

-OW-

Image: Copyright Fir0002/Flagstaffotos. A Cumulonimbus incus over Swifts Creek, Victoria, Australia.

References: http://epod.usra.edu/blog/2009/08/cumulonimbus-incus.html http://www.nssl.noaa.gov/projects/vortex2/learn/glossary.php http://www.clouds-online.com/

Cloud shadows Supercell cumulonimbus clouds some ten km high are casting shadows hundreds of kilometres long as dawn or dusk illuminates the surface of our blue marble as seen from the best vantage point of all: the International Space Station. Loz Image credit: Reid Wiseman

Cloud shadow from Mauna Kea. The sun has just set over the Pacific ocean, but from 4,200 metres up by the dome of the giant Keck telescope atop the shield volcano's summit, its rays can be seen casting shadows of cumulonimbus clouds onto higher thinner clouds above. Loz Image credit: Bill Golish via EPOD.

Timelapse videographer partners with the World Meteorological Association to tell the story of clouds.

Whoa.

Anvil

Astronaut Tim Peake shared this photograph of a developing thunderstorm earlier this week. It is an excellent example of an active cumulonimbus or anvil cloud.

A cloud like this one starts with heated, humid air. Once that air becomes less dense than the surroundings, it rises. The rising air cools, allowing moisture to condense into small liquid droplets or even ice. This condensation releases more energy that heats the air relative to the surroundings, driving the rising air even farther upwards and creating a runaway process.

The Earth’s atmosphere has several different layers. The lowermost layer of the atmosphere, the layer we live in, is called the troposphere. With increasing elevation in the troposphere, the air gets colder, but in the layer above, things change. Temperature drops with increasing elevation in the troposphere, but temperature rises with increasing elevation in the stratosphere. Consequently, rising air in a thunderstorm can rise all the way to the tropopause, the level where temperatures stop going down and start going up again, but it can’t rise farther than that. The developing storm cloud spreads out as a flat layer at this boundary.

The tiny area where the clouds have risen above the flat layer is also distinctive of this type of storm. The one place where the cloud penetrates up into the stratosphere is called an “overshooting top”. In that part of the cloud, there is enough momentum developed by rising air in the column below that the tropopause doesn’t immediately stop the upwelling air. Instead, the air rises just slightly above the tropopause while that momentum is used up.

-JBB

Image credit: Tim Peake https://twitter.com/astro_timpeake/status/724894080011014145

References: http://earthobservatory.nasa.gov/IOTD/view.php?id=8542 http://bit.ly/1SH5UPg

Storm Views

Even if you don’t live someplace that has frequent thunderstorms, you probably know what an anvil cloud looks like. The flat-topped cumulonimbus clouds are a favorite of photographers and videographers, especially when they put on a spectacular lightning display. Ever wonder what these clouds look like from the air? NASA's DC-8 airborne science laboratory spent part of this year studying how large thunderstorms affect atmospheric chemistry. Of course they took a few photos while they were at it, including a side-by-side shot of a thunderstorm supercell they were analyzing in Oklahoma. The cloud top was estimated at 13,700 meters (45,000 feet) high.

Not high enough for you?

NASA Astronaut Kjell Lindgren, currently living on the International Space Station, snapped a photo of one from the ISS. Even from orbit, the flat-top of the storm cloud is apparent.

Photo Credit: Ground: Nicholas A. Tonelli http://bit.ly/1j65Lty Air: NASA/Frank Cutler Space: NASA Astronaut Kjell Lindgren References: http://go.nasa.gov/1L5rvgK http://bit.ly/1VCIocF

Tornado that lasted for a minute - strange weather

Last month, a strange weather pattern wreaked havoc around southern West Bengal in India. The locals called it "the Mini tornado". Although it lasted for only a minute, massive trees were uprooted, tree trunks of more than a foot in diameter were sliced in half, and tin sheds and rooftops were flung a few miles away. Tornados are a rare occurrence in this part of the world; the most recent large tornado was in 2010 when a massive tornado hit the area of Assam, Bihar, West Bengal, and neighbouring Bangladesh. 140 deaths were reported in that tornado which lasted about 20 minutes, with West Bengal alone recording 44 deaths. The 2015 "mini tornado" surprised the locals as they haven't seen such a tornado in at least the last 20 years. Many blame the government for inadequate infrastructure and non availability of early warnings.

The villages of Panchla (in Howrah district) and Habra (in district North 24 Parganas) of West Bengal suffered massive damages on 28th July and 29th July, respectively. The meteorologists attribute this damage to an erratic low pressure belt over Bay of Bengal. At first, it stood still for three days, then started moving inland, and when it was 300 kms. away from Kolkata city, it shifted again moving 340 kms. away from the city. This varied motion led to the formation of multiple small twisters around the depression area which spread over an expanse of 300 kms. of sea within the pressure belt. The small twisters, dense clouds, high windspeeds of 60 - 70 kms. per hour, and heavy, localised downpours occurred in certain parts of the state throughout the week. According to Gokul Chandra Debnath, climate scientist and Director of Alipore Meteorology Department, "the low pressure belt that created funnel shaped towering cumulonimbus clouds could form destructive tornadoes, sometimes." He further states that only by studying the weather phenomenon carefully would meteorologists be able to provide the exact reasons for such strange weather conditions. Meteorologists from Alipore Weather Department, West Bengal went for an on site inspection.

--RB.

Further information: http://bit.ly/1gtYaUS http://bit.ly/1SQUgRU Image: http://bit.ly/1Ubpl54

Cumulonimbus Incus

A cumulonimbus incus is a subspecies of a cumulonimbus cloud, a vertical cloud formed when water vapor is carried by powerful upward air currents and associated with atmospheric instability and thunderstorms. In Latin the word literally means 'heaps of rain'. Cumulonimbus clouds can evolve into a variety of other (often spectacular-looking) clouds such as mammatus, pannus, pileus, venum or tuba clouds.

A mature Cumulonimbus incus (heaps of rain with an anvil shaped top) has reached the boundary between the troposphere and the stratosphere (at approximately 9km height), the tropopause. Here air ceases to cool with height and becomes utterly dry. Because of this abrupt change the cloud flattens and takes on an anvil shape. Remarkably, in equatorial regions the tropopause lies at a much higher altitude of 18km.

It should not be surprising that the Cumulonimbus incus can produce dangerous atmospheric disturbances such as hail, heavy rain, strong winds, lightning and in some cases tornadoes.

If the correct atmospheric conditions are met these giants can eventually turn into supercells.

See here for a timelapse video of how these clouds are formed (and disappear): https://www.youtube.com/watch?v=C3Ny9lddzUk%2F

-OW-

Image: Copyright Fir0002/Flagstaffotos. A Cumulonimbus incus over Swifts Creek, Victoria, Australia.

References: http://epod.usra.edu/blog/2009/08/cumulonimbus-incus.html http://www.nssl.noaa.gov/projects/vortex2/learn/glossary.php http://www.clouds-online.com/

Thunderstorm from space Photography on the space station has had a focus towards clouds and skyscapes over the past months as part of a dedicated project, resulting in some beautiful photos. Here a large anvil supercell (some 200 km across) is silhouetted against the limb of our blue orb, revealing clearly the layers of the atmosphere somewhere over northern Australia around 1,500 km from the station, which was then flying over Papua New Guinea.  The anvil convection cell is strong enough that the rising air and its condensing moisture (remember that clouds are poetically expressed as physics, written in the sky) bump against the next layer of air, spreading out below it. The hues of the lower atmosphere are due to dust and aerosols in the air reflecting red and yellow, much as they do during a sunset, in contrast to the bright blue scattering in the layer above. Astronauts note that the camera just doesn't capture the subtleties of layering in the real atmosphere, that fragile bubble that shields us from the harshness of the medium beyond. Loz Image credit: NASA http://earthobservatory.nasa.gov/IOTD/view.php?id=84778&src=fb