Changes in the atmosphere

CHANGES IN THE ATMOSPHERE

What is the difference between weather and climate?WEATHER is the average condition of the

atmosphere over a short period of time in a particular space.

CLIMATE is the typical weather condition in a particular space during a long period of time

FACTORS AFFECTING WEATHER

1) AIR TEMPERATUREThe temperature of the air is due to the heat

absorbs from or gives off to the environment.SPECIFIC HEAT of a substance is defined as

the total amount of energy to raise a temperature of 1gram of a substance to 1oC.

If a material has a low specific heat , then it heats up faster compared to an equal amount of material with a high specific heat.

FACTORS AFFECTING WEATHER2) AIR PRESSUREAir exerts force on all objects.The force exerted by air is due to the Gravitational force

of the earth.PASCAL (Pa) – is the SI unit of air pressureAir pressure is influenced by altitude.

When all factors are equal, air pressure decreases as altitude increases. Conversely, air pressure increases as altitude decreases.

Gravity tends to pull as many air molecules as possible closer to the center of the EARTH.

It is harder to breathe or take in more oxygen at reduced pressure.

Air pressure is always pressing on your body.

BAROMETER is the instrument used to measure air pressure.

FACTORS AFFECTING WEATHER

HumidityHumidity is the amount of water vapour

present in the air.If the air is damp and moist, the possibility of

condensation is higher than evaporation.If the air is dry, there is a higher chance of

evaporation than condensation, so the air is said to have low humidity.

FACTORS AFFECTING WEATHER

PrecipitationClouds do not remain in the sky for a long

time. They grow and become heavy as more water vapour condenses. When they become too heavy, they fall back on earth. This process is called PRECIPITATION.

RAIN is the most common type of precipitation. It is also the easiest to measure.

RAIN GAUGE measures the amount of rainfall.

OTHER FORMS OF PRECIPITATION

Drizzle - rain of very fine drops which are very close to each other and fall very slowly.

Snow – falls when ice crystals fail to melt before they reach the ground.

OTHER FORMS OF PRECIPITATION

OTHER FORMS OF PRECIPITATION

Hail is the precipitation in the form of pellets made of layers of ice and snow.

OTHER FORMS OF PRECIPITATION

Sleet – frozen rain.

FACTORS AFFECTING WEATHER

WindWinds are generated by the differences in the

temperature that occur on the Earth’s surface.

The rising and sinking of the air generate movement in the atmosphere. This pattern is called convection, the transfer of heat through moving particles of air.

The instrument used to determine the direction of the wind is called a wind vane

Anemometer is used to measure the speed of the wind blowing in a place.

Breezes

The rising and sinking of the

air creates local winds. Local

winds can easily be felt on areas near a body of water or areas

near a mountain.

SEA BREEZE

During the day, the air over the land is warmer and less dense than the air over the land is warmer and less dense than the air over the sea. This causes the air over the land rise and as it does, the air over the sea replaces the rising air.

LAND BREEZE

At night, this process is reversed. The air over the sea is warmer than air over the land. Thus, warm air over the sea rises and cold air over the land moves towards the sea.

Wind systems in the Philippines

Winds that blow by seasons toward either the continents or oceans because of the differences in air pressure and air temperature are called monsoons.

In the Philippines, two seasonal wind system affect its climate:

1. the Southwest Monsoons or Hanging Habagat

2. the Northeast Monsoons or Hanging Amihan.

SOUTHWEAST MONSOON

The southwest monsoon is caused by the warm air passing over the ocean in the equator. Because of this, air acquires moisture from evaporating water which brings considerable amount of rain as it hits land. This warm, moist air actually comes from Indian Ocean.The hanging habagat visits the Philippines from the months of June to September. It customarily produces abundant rain, causing strong winds and wet climate in the country.

NORTHEAST MONSOON

Northeast monsoon or hanging amihan brings cool and dry winds formed from the regions of Mongolia, Siberia, and Northern China during winter seasons. It brings calmer and cooler climate in the Philippines and is experienced from November to February.

Weather Disturbances

The most destructive weather disturbance is the tropical cyclone. They are called typhoons in the Philippines in the western North Pacific Ocean, cyclones in the Indian Ocean, and hurricanes in the eastern North Pacific and North Atlantic Ocean.

Table 10.1 TROPICAL CYCLONE INTENSITY AND CATEGORY

CATEGORY MAXIMUM WINDSTROPICAL DEPRESSION Between 35 kph and 64 kph near

the centerTropical storm Between 65kph and 118 kph near

the centerTyphoon 119-200 kph near the center

Super typhoon Maximum winds greater than 200kph

How does typhoon form?

INTERTROPICAL CONVERGENCE ZONE