Introduction:
The weather we see day to day may see drab and normal (especially if you live in England) but on rare occasions we see some outstanding views of the might of Earth's weather; things we cannot comprehend. Well in this blog I am, hopefully, going to un-veil some of the mysteries behind a few of these phenomena.
Moonbows:
By definition, a Moonbow is a rainbow produced by light reflected off the surface of the moon refracting off of moisture in the air.
These are a mostly unheard-of experience, and this is because they are a very rare sight, for two reasons:
1. The often appear very faintly or white in colour because they're too faint to excite the cone colour receptors in human eyes, so they are harder to detect. (look up what 'cone colour receptors' are: http://simple.wikipedia.org/wiki/Cone_cell)
2. For true moonbows, other than those produced by waterfalls or sprays,
the moon must be low in the sky (less than 42 degrees and preferably
lower) and the sky must be very dark. Since the sky is still light on a
rising full moon, this means they can only be observed 2 to 3 hours
before sunrise, a time with few observers. And, there must be
rain falling opposite the moon.
A great example of a great location to spot moonbows is Victoria Falls in Zamibia:
http://www.youtube.com/watch?v=LPD7sfeqSOo
A great example of a great location to spot moonbows is Victoria Falls in Zamibia:
http://www.youtube.com/watch?v=LPD7sfeqSOo
 |
Victoria Falls |
Lightning:
Now, we've all seen and heard of lightning, and it's partner in crime, thunder, but do we know why it occurs? Lightning is a massive electrostatic discharge between the electrically charged regions within clouds or between a cloud and the ground. The charged regions within the atmosphere temporarily balance themselves through a lightning flash, commonly referred to as a 'strike' if it hits an object on the ground.
There are three primary types of lightning:
Cloud to Ground: Lightning that occurs between the cloud and the ground.
Fire Whirls:
Definition: Fire-whirls are whirlwinds of flame that may occur when extreme heat and very fast wind conditions combine to form whirling vortex of air. These vortexes can tighten into a tornado-like structure that sucks in burning debris and gases.
Alternative names: fire devils, fire tornadoes or firenados
A fire tornado consists of a core, which is the part on fire, and an invisible pocket of spiralling air that feeds fresh oxygen to the core. The core of a typical fire tornado is 1 to 3 feet (0.30 to 0.91 m) wide and 50 to 100 feet (15 to 30 m) tall. Under the right conditions, very large fire tornadoes, more than 300 meters tall, can form. The temperature inside the core of a fire tornado can reach up to 1,090 °C , which is hot enough to potentially reignite ashes sucked up from the ground. Often, fire tornadoes are created when a wildfire or firestorm creates its own wind, which can turn into a spinning vortex of flame. Fire tornadoes can set objects in their paths on fire and can chuck burning debris out into their surroundings as they whirl onwards. The winds generated by a fire tornado can also be dangerous as they can create wind speeds of more than 100 miles per hour, which is definitely strong enough to knock down trees and dislodge unstable buildings/ debris.
Example: (2003) During the Canberra bushfires, a fire tornado with a diameter of nearly 500 metres with horizontal winds exceeding 160 mph was documented. Further research into the fires confirmed this in 2012.
There are three primary types of lightning:
- from a cloud to itself (intra-cloud or IC)
- from one cloud to another cloud (CC)
- and between a cloud and the ground (CG)
Lightning is not distributed evenly around the planet. About 70% of lightning occurs over land in the tropics where atmospheric convection is the greatest. This occurs from both the mixture of warmer and colder air masses, as well as differences in moisture concentrations, and it generally happens at the boundaries between them. The flow of warm ocean currents past drier land masses, such as the Gulf Stream, partially explains the elevated frequency of lightning in the Southeast United States.
Because the influence of small or absent land masses in the world's oceans, lightning is notably less frequent there
than over larger landforms. The North and South Poles are limited in their coverage of thunderstorms and therefore result in areas with the least amount of lightning.
Intra-cloud lightning: The most common type of lightning. It happens completely inside the cloud, jumping between different charge regions in the cloud. Intra-cloud lightning is sometimes called sheet lightning because it lights up the sky with a 'sheet' of light.
Cloud to Cloud: Lightning that occurs between two or more separate clouds.
Cloud to Ground: Lightning that occurs between the cloud and the ground.
 |
| Forked Lightning |
General Lightning Facts:
- In general, cloud-to-ground (CG) lightning flashes account for only 25% of all total lightning flashes worldwide.
- Lightning is usually produced by cumulonimbus clouds, which have bases that are typically 1-2 km (0.6-1.25 miles) above the ground and tops up to 15 km (9.3 mi) in height.
- Lightning causes an average of 80 deaths and 300 injuries each year.
- The energy from one lightning flash could light a 100 watt light bulb for more than 3 months.
- Only about 10% of people that are struck are actually killed. 90% survive, but nearly 25% of these survivors suffer long term psychological or physiological trauma.
- 92% of lightning injuries and deaths occur between May and September.
- 45% of the deaths and 80% of injuries occurred in these months between 10am and 7pm.
- Lightning can strike more than 10 miles away from any rainfall. More than 50% of lightning deaths occur AFTER the storm has passed.
Belt of Venus:
Definition: The Belt of Venus is an atmospheric phenomenon seen at sunrise and sunset (so not entirely a weather phenomenon). Shortly after sunset or shortly before sunrise, the observer is, or is very nearly, surrounded by a pinkish glow that extends roughly 10°–20° above the horizon. Often, the glow is separated from the horizon by a dark layer, the Earth's shadow. The Arch's light rose (pink) colour is due to reflection of reddened light from the rising or setting Sun. |
The Belt of Venus
|
Fire Whirls:
Definition: Fire-whirls are whirlwinds of flame that may occur when extreme heat and very fast wind conditions combine to form whirling vortex of air. These vortexes can tighten into a tornado-like structure that sucks in burning debris and gases.
Alternative names: fire devils, fire tornadoes or firenados
A fire tornado consists of a core, which is the part on fire, and an invisible pocket of spiralling air that feeds fresh oxygen to the core. The core of a typical fire tornado is 1 to 3 feet (0.30 to 0.91 m) wide and 50 to 100 feet (15 to 30 m) tall. Under the right conditions, very large fire tornadoes, more than 300 meters tall, can form. The temperature inside the core of a fire tornado can reach up to 1,090 °C , which is hot enough to potentially reignite ashes sucked up from the ground. Often, fire tornadoes are created when a wildfire or firestorm creates its own wind, which can turn into a spinning vortex of flame. Fire tornadoes can set objects in their paths on fire and can chuck burning debris out into their surroundings as they whirl onwards. The winds generated by a fire tornado can also be dangerous as they can create wind speeds of more than 100 miles per hour, which is definitely strong enough to knock down trees and dislodge unstable buildings/ debris.
Example: (2003) During the Canberra bushfires, a fire tornado with a diameter of nearly 500 metres with horizontal winds exceeding 160 mph was documented. Further research into the fires confirmed this in 2012.
 |
| Australian Firenado |
