Challenge of Natural Hazards: Weather Hazards: Tropical storms

Global atmospheric circulation:

Key terms:

• Insolation: the amount of solar radiation (sunlight) an area receives

• Convection cell: a worldwide system of winds moving heat from the equator to the poles to reach a balence in temperature

• Albedo effect: how well different surface reflect sunlight back into space

• Prevailing wind: the most frequent wind direction a location experiences

• Jet streams: strong, fast moving wind banks which are found at high altitudes, just below the tropopause.

• Global circulation: the movement of air accross the planet in a specific pattern.

• Differential heating: the uneven heating of the earths surface due to differences in its composition

The Coriolis Effect:

The coriolis effect is the deflection or bending of the wind due to the rotational spin of the Earth.

• THERE IS NO CORIOLIS EFFECT AT THE EQUATOR

• When air travels north from the equator to the poles, it moves east

• When air travels south from the poles towards the equator, it moves west

The Hadley cell:

• From 0-30 degrees above and below the equator

• The largest of the cells

• Very low pressure zone

• Tropical rainforests

• Very hot and humid

  • Winds blow from the tropical regions to the equator and travel in an easterly direction

  • Near the equator, the winds meet, and the hot air rises and form thunderstorms (tropical rainstorms)

  • From the top of these storms, air flows towards higher latitudes, where it becomes cooler and sinks over subtropical regions

  • This brings dry, cloudless air, which is warmed by the Sun as it descends – the climate is warm and dry (hot deserts are usually found here)

The Ferrel cell:

• From 30-60 degrees

• High pressure zone

• Travel in a different direction to the other cells

• Low amounts of rainfalls

• Hot dessert region

• Not driven by temerature

  • Air in this cell joins the sinking air of the Hadley cell and travels at low heights to mid-latitudes, where it rises along the border with the cold air of the Polar cell

  • This occurs around the mid-latitudes and accounts for frequent unsettled weather (particularly the UK)

The Polar cell:

• High pressure zone

• 60-90 degrees

• Icy desserts

• No rainfall

  • Air in these cells is cold and sinks, creating high pressure over the highest latitudes

  • The cold air flows out towards the lower latitudes at the surface, where it is slightly warmed and rises to return at altitude to the poles

Tropical Storms:

Natural Hazard - a naturally occuring event that causes death, damage or destruction

Tropical storms - when tropical warm air rises to create an area of intense low pressure - as the warm, moist air reaches a high altitude, powerful winds spiral around the calm centeral point, creating the eye - the warm air cools and condenses into heavy rainfall and thunderstorms

Deggs Model:

When the natural hazard is a potential to interact with a vunerable population then there was no interaction, and no disaster. When a natural hazard interacts with a vuenrable population, then a disaster has occured.

Global Distrubution Of Tropical Storms:

Tropical storms are found between the tropic of cancer and the tropic of capricorn at 23.5* north and south of the equator.

The ‘Ingredients’ Needed For A Tropical Storm:

a) Sea temperatures above the critical 27*C and deep water - provides heat and moisture that causes the warm air to rise rapidly in low pressure zones, latent heat is released which powers the storm

b) Not along the Equator - tropical storms need the coriolis effect to spin the gain energy NO CORIOLIS EFFECT AT THE EQUATOR!

c) Low wind sheer - (winds which remain constant and dont vary in height) means that tropical storm clouds can rise to high levals without being torn apart.

How A Tropical Storm Forms:

1. The sun sends incomming solar radiation (insolation) to Earth, heating tropical oceans to a critical 27*C

2. Air above the surface of the oceans is heated

3. Warm moist air rises through the air as thermals (upwards currents of warm air). This gives low pressure

4. The air cools as it rises at 1*C per 100m; this causes condensation to occur, cumnlonibus clouds to form and torrential rain to fall

5. Some cooled air sinks back down helping to create the eye; here conditions are dry and calm

6. The Coriolis effect causes the air to spin upwards around a calm central eye. The Coriolis effect bends winds counterclockwise in the northern hemisphere and clockwise in the southern hemisphere

7. The tropical storm travels across the ocrean in the prevailing wind

8. When the storm meets land, it is no longer fulled by the source of moisture and heat from the ocrean so it looses power and weakens. As they pass over land, friction also slows the storm.

The Structure And Features Of A Tropical Storm:

The eye:

• Relitevly calm

• Generaly clear area of sinking air and light

• Center of the storm

• Winds usually do no exeed 15mph or 20-40 miles wide

The eye wall:

• Consists of a ring of tall thunderstorms that produce heavy rain and the strongest winds

• You can get double eye walls

• Changes in the eye/eye wall can cause changes in wind speed

Rainbands:

• Curved bands of clouds/thunderstorms that trail away from the eye wall in a spiral

• Can have gaps in between spiral rain bands where no rain or wind is found.

The Effects Of A Tropical Storm:

Primary effects:

the initial impacts of a tropical storm, there a three primary effects

• Strong winds (119 KMph or 73mph)

• Torrential rain (500 mm in 24hrs)

• Storm surges

Secondary effects:

the indirect impacts of a tropical storm. Secondary effects include

• Flooding

• Landslides

• Contamination of water sources

Q: Describe three ways that tropical storms affect (a) people and (b) the enviroment

One way that tropical stroms affect people is that it can lead to homelessness as houses are destroyed by flooding. A primary impact on the enviroment is falling trees due to strong winds exeeding 73mph. A secondary impact on humans in contaminated water which becomes unsafe and unhygenic, potentially leading to the spread of diseases.

How Tropical Storms Are Measured:

The Responses To A Tropical Storm:

Case Study: Typhoon Haiyan

On the 8th November 2013 at 4.40 am local time, Typhoon Haiyan hit the Philippines. The Philippines experience an average of 20 major storms each year, Typhoon Haiyan was the 25th to enter Filipino waters in 2013. It was marked a 5 on the Safir-Simpson Sale.

How Monitoring, Prediction, Protection And Planning Can Reduce The Effects Of Tropical Storms:

Monitoring: allows predictions to be made which can save lives and reduce dammage

• The global precipitation measurement satalite was launched in 2014. It moniters precipitation every three hours between latitudes 65* North and South of the Equator to identify high-altitude rain clouds.

• Aircrafts such as the Global Hawk drone can fly into the tropical storms and conduct research.

Prediction:

• Super computers can be used to create models that predict the path and the intensity of the storm

• The met office promises that its new computer will sabe the economy alot of money in weather disruption

Protection:

Buildings have weaknesses which can be reinforced to reduce damage caused by forceful winds of tropical storms. This is caused mitigation. Examples:

• Intall hurricane straps (galvanised metal) between the roof and walls

• Intall storm shutters on windows

• Install emergancy generators

Planning:

Many countries have set times of the year where they encorage people to plan for what they need to do in the event of a tropical storm. In America National Hurricane preparedness week is in May.

The Impact Of Climate Change On Tropical Storms:

CLIMATE CHANGE: THE LONG-TERM CHANGE IN THE EARTHS CLIMATE, ESPECIALY A CHANGE DUE TO AN INCREASE IN THE AVERAGE ATMOSPHERIC TEMPERATURE>

Tropical Storm FREQUENCY: The overall frequency of tropical storms is expected to either remain the same or decrease slightly. In the last two decades there have been several years with a higher number of storms but - but the pattern is eratic

Tropical Storm INTENSITY: Due to greater warming of the oceans, tropical storms are likely to get more intense by 2-11% by 2100. This is becuase of more evaporation and more cloud.

Tropical Storm DISTROBUTION: The regions whre tropical storms are experienced are not expected to change significantly due to climate change. Tropical storms could move slightly furthur north and south of the equator becuase more areas have a sea temperature of 27* C or more.