TROPICAL STORM

TROPICAL STORM

Occurs in the coastal areas in the tropics

Bring heavy rainfall and strong winds speed about 200 km per hour

Accompanied by thunder and lightning

In Japan, China & the Philippines are called Typhoon

In Bangladesh and Australia is known as Tropical Cyclones

Atlantic areas they are called Hurricanes

THE FORMATION OF TROPICAL STORM


Develop over the warm oceans when the surface temperatures exceed 27◦C
When air over the sea get heated, it expands and rises very rapidly.
This create an area of intense low pressure.
Warm moist air rises to a great heights, condensing to form clouds and rain.
Air from the surrounding higher pressure area rushes inward in a spiraling manner to replace the rising warm air.
The air spin in at speed of about 200 km per hour, absorbing large amount of moisture and forming cumulonimbus clouds and heavy rains.

The cold air then sink, the centre of the storm is called the eye in area of calm weather marked by clear skies

 

THE EFFECTS OF TROPICAL STORM

Destroy life – especially in the populated areas
Destroy property- uproot trees, destroy crops and houses
Storm surges- when strong winds raise the ocean surface into a giant waves and destroy coastal settlements and flood large areas.
Flood – a covering water over land which is normally dry which are related to weather.

a) continuous rain- a longer period of rain, when the water cant seep inside the ground and more runoff

b) snow melt- snow melt and increase the volume of water in the river and runoff

c) storm surge

Droughts- unusual long period during which little or no rain falls.

CASE STUDY : BANGLADESH

Storm surges 19th April, 1990 in Bangladesh

Huge waves up to 7 m high

Destroy hundred thousand of trees

Killed 132, 000 people

Injured 458,000

Loss of large portion of their land and fish farms

Storm Surge in Bangladesh

Precipitation

Precipitation is caused when moist air rises, water vapour in the air cools  and  condenses  to forms clouds.

Air cools upwards through the atmosphere because temperature falls with altitude because the Earth’s atmosphere is heated from the Earth’s surface up over.

When the water droplets in clouds grow to a certain size, gravity causes them to fall because of their own weight. Water droplet will fall as rainwater or precipitation.

Three main types of precipitation

1.Convectional rainfall

Convectional rainfall is more common in Brunei. It occurs in areas with hot, humid climates like equatorial regions.

This type of rain happens when the earth gets so hot that the warm air mass above it rises.

The air cools, condenses and cumulonimbus clouds form.

Heavy rainfall with thunder and lightning follows.

CONVECTIONAL RAINFALL

2.Relief rainfall

Relief rainfall occurs where the air over the sea moves over the land and is forced to rise over hills or a mountain range.

This air cools, condenses and forms clouds – the result is rain.

As the air descends the mountain on the other side, it warms and sinks.

Much less rain occurs on this side of the mountain. (Rainshadow)

RELIEF RAINFALL

3.Frontal rainfall

This rain occurs when a warm air mass meets a cool air mass.

The warm air mass is forced to rise over the cold air mass.

When the warm air rises it cools, condenses and forms rain clouds.

FRONTAL RAINFALL

CLOUD

The Formation of the cloud

Formation of Cloud

A diagram showing how the formation of cloud

TYPES OF CLOUD

Cirrus- high level cloud, composed of ice crystal than water thin, fine weather wispy, sunset

CIRRUS

Cumulus-massive rounded ,flat base,extend to great height, fair weather

CUMULUS

Stratus- low greyish,sheet layers, cover entire sky,light drizzles

STRATUS

Cirrocumulus- white round masses

CIRROCUMULUS

Cumulonimbus- are cumulus clouds, great vertical extent, heavy rain, warm morning, afternoon bring convectional rain, lightning and thunders

CUMULONIMBUS

Stratonimbus-dark rain clouds

Stratocumulus- lumpy and grayish

RELATIVE HUMIDITY

Relative humidity refers to the ratio between the actual amount of water vapour in a given volume of air at a particular temperature and the total amount of water vapour needed to saturate the given volume of air at that temperature.

FORMULA

RELATIVE HUMIDITY=  AMOUNT OF WATER VAPOUR IN THE AIR     X          100%

TOTAL AMOUNT OF WATER VAPOUR NEEDED TO SATURATE AIR

HYGROMETER

wet and dry bulb thermometer (hygrometer)

Digital Hygrometer

Humidity Counts

How to calculate the Relative Humidity

The dry bulb thermometers measures 22 C and the wet bulb thermometer measures 21 C , the wet bulb depression is then 1 C. When the wet bulb depression is 1 C and the dry bulb thermometer is 22 C , the relative humidity is 90% . A relative humidity of 90% indicates that there is a lot of moisture in the air at that temperature.

WINDS

WINDS ARE MOVEMENT OF AIR FROM HIGH PRESSURE TO LOW PRESSURE AREAS.

WIND CAN OCCUR ON A SMALL SCALE AND LARGE SCALE
1.LAND AND SEA BREEZE IS AN EXAMPLE OF SMALL SCALE
2. MONSOON WINDS AND PLANETARY ARE EXAMPLE OF LARGE SCALE.

LAND BREEZE AND SEA BREEZE

land and sea breeze

 

Planetary Winds

Planetary winds are winds that blow out from high pressure belt to low pressure belts.

There are three types of Planetary winds

1.Trade Winds

2.The Westerlies

3.The Easterlies


PLANETARY WINDS

The planetary winds blow in curved/deflected direction due to the rotational of the earth.

The wind deflect to the right in Northern Hemisphere and left to the Southern Hemisphere

Equator is an area of low pressure and the 30◦ N and 30◦S is the high pressure area.

Wind deflect to the right from the equator is called the North East Trade in the Northern Hemisphere

Winds deflect to the left from the equator  is called South East Trade in the Southern Hemisphere.

 

Monsoon Winds

Monsoon winds is another example of large scale wind which occurs on a regional level and blows over large land masses.

Monsoon ‘ mausin’ in arabic means season

The unequal heating and cooling of large land masses and the oceans causes a difference in pressure. This causes in the movement of large scale winds whose direction changes with each season.

Monsoon winds blow over Southern and Eastern Asia and influence the climate in these regions.

NORTH EAST AND SOUTH WEST MONSOON

 

INSTRUMENTS FOR WIND

WIND VANE

DIRECTION- EAST,WEST,NORTH & SOUTH

WIND VANE IS USED TO FIND DIRECTION

ANEMOMETER

UNIT MEASUREMENT IS IN KM PER HOUR

 


ANEMOMETER IS USED TO MEASURE THE SPEED OF THE WIND

 

WIND ROSE

Wind roses summarise the occurrence of winds at a location, showing their strength, direction and frequency.

 

BEAUFORT SCALE

 

The Beaufort Scale is an empirical measure for describing wind speed based mainly on observed sea conditions

 

 

 


AIR PRESSURE

DEFINITION
AIR PRESSURE IS THE DOWNWARD FORCE EXERTED BY THE WEIGHT OF AIR PER UNIT AREA ON THE EARTH’S SURFACE.
AIR PRESSURE MAY VARY WITH ALTITUDE AND TEMPERATURE.
AIR PRESSURE IS GREATER AT THE SEA LEVEL AND DECREASES WITH INCREASING ALTITUDE.

INSTRUMENT USED
BAROMETER

BAROMETER

MERCURY BAROMETER

ANEROID BAROGRAPH

ANEROID BAROMETER

ISOBARS IS THE LINES ARE JOINING PLACES WITH EQUAL PRESSURE.
UNIT MEASUREMENT IS IN MILLIBARS
TYPES OF PRESSURE
RISING WARM AIR IS LESS DENSE AND EXERTS LOW PRESSURE.

SINKING COLD AIR IS MORE DENSE AND EXERTS HIGH PRESSURE.

AS THE RESULT OF THE DIFFERENCE IN AIR PRESSURE BETWEEN TWO PLACES WIND IS FORMED.

HIGH PRESSURE + LOW PRESSURE = WINDS

FACTORS INFLUENCE THE TEMPERATURE

1.LATITUDE
TEMPERATURE ARE HIGHER AT OR NEAR THE EQUATOR
IF AWAY(NORTH & SOUTH POLE) FROM THE EQUATOR TEMPERATURE ARE LOWER
REASONS
FOR THIS IS THE SURFACE OF THE EARTH’S PART IS CURVED. AS THE RESULT, THE SUN ‘S VERTICAL RAY STRIKE DIFFERENT PARTS OF THE EARTH SURFACE AT DIFFERENT ANGLES. AT THE EQUATOR, THE VERTICAL RAYS HIT THE EARTH’S SURFACE AT AN ANGLE OF 90◦(ANGLE OF INCIDENCE) TOWARDS THE POLES.
2. ALTITUDE
ALTITUDE IS THE HEIGHT ABOVE THE SEA LEVEL
HIGH ALTITUDE (AT THE MOUNTAIN), LOW TEMPERATURE
LOW ALTITUDE (ON LAND SURFACE), HIGH TEMPERATURE
REASONS
AT THE HIGHER ALTITUDES , THE AMOUNT OF ATMOSPHERE DECREASES AND AS THE RESULT THERE IS LESS WATER VAPOUR IN THE AIR. THE ATMOSPHERE ABSORBS LESS HEAT AND THEREFORE THE TEMPERATURE AT HIGHER ALTITUDE DROPS.
3.DISTANCE FROM THE SEA
THE DIFFERENCE IN HEATING OF LAND AND WATER AFFECTS THE TEMPERATURE OF PLACES LOCATED NEAR THE COAST DIFFERENTLY FROM THOSE LOCATED INLAND.
MARITIME INFLUENCE
WHEN THE SEA IS COOLER THAN THE LAND IN SUMMER, IT LOWER THE TEMPERATURE OF COASTAL PLACE. HOWEVER , DURING THE WINTER THE SEA IS WARMER THAN THE LAND AND KEEP COASTAL PLACES WARMER BY MODERATING THE WINTER TEMPERATURE.
CONTINENTAL INFLUENCE
LOCATED IN THE INTERIOR OF LARGE CONTINENTS  OR LAND MASSES ARE UNDER CONTINENTAL INFLUENCE, THAT IS,THE SEA DOES NOT AN EFFECT ON THEM AS THEY ARE TOO FAR IN TEMPERATURES. AS LAND HEATS UP RAPIDLY, INLAND LOCATIONS TEND TO HAVE HOTTER SUMMERS THAN AREAS NEAR THE COAST IN SIMILAR LATITUDES.
4. OCEAN CURRENTS
OCEAN CURRENTS ARE LARGE STREAMS OF WATER FLOWING IN THE OCEANS. THESE GENERATED WHEN WINDS BLOW OVER THE WATER SURFACE.
THERE ARE TWO TYPES OF OCEAN CURRENTS.
COLD CURRENTS THAT BRINGS WATER FROM THE POLAR REGIONS
WARM CURRENTS THAT BRING WARM WATER TO THE POLAR REGIONS
OCEAN CURRENTS CAN RAISE OR LOWER THE TEMPERATURE OF NEARBY COASTAL AREA.
COASTAL AREA WHICH AFFECTED BY WARM CURRENTS WILL BE KEPT WARM DURING WINTER IF THE COLD CURRENTS MOVE ALONG THE COAST THEY WILL LOWER THE TEMPERATURES OF THE AREA.
5. HUMIDITY
HUMIDITY IS THE AMOUNT OF WATER VAPOUR IN THE ATMOSPHERE AND ITS INFLUENCES THE CLOUD COVER IN THE SKY.
THE HIGHER THE HUMIDITY THE GREATER AMOUNT OF CLOUD COVER.
THE LOWER THE HUMIDITY THE LESS AMOUNT OF CLOUD COVER.

6.CLOUD COVER
PLACE NEAR THE EQUATOR HAS GREATER AMOUNT OF CLOUD COVER
AREAS IN THE DESERT WHERE HUMIDITY IS LOW WILL HAVE LOWER AMOUNT OF CLOUD COVER.
7. ASPECT
ASPECT IS THE DIRECTION IN WHICH A SLOPE FACES IN RELATION TO THE SUN.
IN THE TROPICAL AREAS THE ASPECT IS NOT MUCH IMPORTANCE BECAUSE THE SUN IS HIGH IN THE SKY DURING MID DAY.
IN THE TEMPERATE AREAS, THE SUN IS LOW ANGLE IN WINTER, THIS WILL AFFECT THE TEMPERATURE OF SLOPES THAT FACE NORTH TO SOUTH. IN NORTH HEMISPHERE, THE SOUTH FACING SLOPE RECEIVE GREATER CONCENTRATION OF SOLAR RADIATION AND USUALLY WARMER THAN THE NORTH FACING SLOPE.
8. TYPES OF LAND SURFACE
DENSE FOREST– THE VEGETATION PREVENTS SOLAR RADIATION FROM REACHING THE GROUND DIRECTLY. THE GROUND REMAIN COOL.
IN THE CITY– THE PRESENCE OF CONCRETE SURFACE TENDS TO KEEP THE AIR TEMPERATURE HIGH. THE CONCRETE SURFACE ABSORB HEAT DURING THE DAY AND RETAIN THE HEAT AT NIGHT.