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Social sciences: geography

Grade 7

Natural hazards

Module 3

Tropical cyclones

1. Tropical Cyclones

  • The occurrence and cause of tropical cyclones

No weather phenomenon is more terrifying and destructive than a tropical storm. In America such storms are called hurricanes, in Asia typhoons, in South Africa tropical cyclones and in Australia Willie-willies.

Features of tropical cyclones

They develop over the warm, tropical oceans near the equator. The warm, tropical seawater heats the air that rests upon it up to temperatures of ± 27°C. The high degree of evaporation makes the air very humid. That is why the tropical easterly winds are chiefly characterized by the fact that they are hot and humid. This causes the air above the oceans to rise swiftly, resulting in extremely low pressure. The convection currents start spiralling at an ever increasing speed. The air rises more and more, and condensation and cumulus and cumulonimbus clouds are formed. The rotation of the earth on its own axis causes the cloud masses to circle, which creates a gigantic, swirling storm.

In the centre of this cyclone there is an eye of moist, cloudless weather that can be about 35-50 km wide. Here atmospheric pressure readings are less than 1 000 hPa. Directly around it storm winds rage at 120-280 km/h. Stormy weather can occur up to 200 km from the eye, and these storms can continue for a few hours or even for a number of days. They move forward slowly (15-20 km/h) and start to subside as soon as they reach the land surface or cooler water. Great destruction, heavy downpours and tidal waves occur for a number of days along the coastal areas of the affected countries.

Traditionally cyclones were named after women because of their capricious nature. Nowadays they are sometimes also named after men. The relentless tropical cyclone “Hugo” that hit the east coast of America in 1989 is one such example.

Such a storm would be indicated on a weather chart by round isobars that are closely positioned around the eye.

Synoptic weather chart

2. The effect (consequences) of tropical cyclones on peoples’ lives and their socio-economic activities

South Africa does not often experience the utter ferocity of a tropical storm. However, when it does occur, it causes just as much destruction as in other parts of the world.

The worst cyclone that has ever been recorded along the South African coast was the tropical cyclone Demoina. On 25 January 1984 Demoina veered inland from a position near Maputo. The following two days it caused violent storms, high winds and a great deal of rain over parts of South Africa. At some places as much as 540 mm was recorded in a period of 24 hours. In Northern Natal rivers burst their banks. Villages near rivers were totally destroyed, bridges were washed away and crops on the banks of the rivers were destroyed. Damage to sugar plantations was estimated at R150 000 000. At least 200 people lost their lives. It was difficult to carry out rescue operations because most of the bridges and roads in the affected areas had been washed away. The gale force winds made conditions extremely hazardous for helicopters. Bodies of victims, and even crocodiles, were washed into the sea. The death toll rose even higher as a result of waterborne diseases and famine.

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Geography grade 7. OpenStax CNX. Sep 09, 2009 Download for free at http://cnx.org/content/col11021/1.1
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