Weather...

Weather... You can’t see me, but you feel me, you can’t

touch me, but I can touch you. I have been called the “Breathe of the Gods”, or the killer and giver of life, gentle and fierce, friendly and enemy, angry and happy. The Native Americans called me Moriah, and Snow Eater (Chinook). The Japanese call me Kaze and in Russia I am called Veter. I can shatter homes, or wake a child from a peaceful sleep or bring relief in times of need. I can spread the most dreaded diseases or bring a welcome freshness. What am I?

Weather is.... The current state of the

atmosphere...what is happening right now

The Earth’s Atmosphere

Main points to remember as we learn about weather:

The sun warms the earth’s surface and therefore all the air above the surface

The earth is warmed most at the equator and least at the poles---why?

The air above land is warmed more quickly than air above water.

Warm air expands and rises, creating an area of low pressure; cold air is heavy and sinks, creating an area of high pressure

High Pressure and Low Pressure

Winds and Air Pressure

Remember… • Rising air and descending air produce

different kinds of weather

Depressions• A Depression is an

area of Low Atmospheric Pressure.

• Depressions are also known as Cyclones.

• Depression often pass over Ireland.

• Depressions bring wet and windy weather. This is why we receive lots of rain.

Anticyclones• An anticyclone is an

area of high pressure.

• Anticyclones bring clear sunny weather.

• There are few clouds and a gentle breeze.

Fronts• When two air masses meet they do not mix very well because of their

different temperature, pressure and humidity.

• Where the two air masses meet is called a Front.

• We will look at two types of Fronts, a Cold Front and a Warm Front.

Fronts: the boundary between 2 air masses

Warm Front: warm air slides over departing cold air- large bands of precipitation form

This is the symbol on a map for a warm front

Cold Fronts Cold air pushes under a warm air

mass. Warm air rises quickly=narrow bands of violent storms form

This is the symbol for a cold front

Occluded Front 2 air masses merge and force

warm air between them to rise quickly. Strong winds and heavy precipitation will occur

This is the weather map symbol for an occluded front

Reading a weather map ISOBAR= connects areas of equal

pressure BAR comes from BARometric pressure

Reading a weather map... Isotherm: Connects areas of equal

temperature; therm means temperature

Understanding the weather• Rte player – weather

• Weather charts

The water cycleWater: a renewable resource

The Water Cycle Keywords

1. Evaporation2. Condensation3. Cloud4. Percipitation5. Run Off

Water

• Water is a basic natural resource needed to maintain human and animal life and to grow food

• It is a renewable resource

The Water Cycle

Run Off

Important terms• 1. Evaporation – Water

transferring from the ground into water vapour in the air.

• 2. Condensation – Water vapour in the air turning back into a liquid.

• 3. Cloud – Water droplets are held in the air in the form of clouds.

• 4. Precipitation – Water that falls to the ground in the form of Hail, Rain, Sleet, or Snow.

• 5. Run – off – Water running over the ground back to the sea.

Activity

• Draw and explain the water cycle into your copies.

• Water cycle song• http://www.youtube.com/watch?v=o3BVa7

PH_JE&feature=youtube_gdata_player

Water Cycle song

Clouds• Clouds are made when water vapour condenses into tiny

droplets.

• There are many different types of clouds.

• The most common types of clouds are;

1. Cirrus Clouds 2. Cumulus Clouds3. Stratus Clouds

TYPES OF CLOUDS Cirrus Clouds: wispy, feathery

clouds Form only at high levels, therefore are made of ice crystals

Types of Clouds Cumulus Clouds: are puffy white

cotton ball looking clouds

Cumulonimbus Clouds These are thunderstorm clouds

Types of Clouds Stratus Clouds: clouds that form in

flat layers- cover all or most of the sky and are low level clouds

Rainfall• Precipitation means hail, rain, sleet or snow.

• Rain is the most common type of precipitation.

• Rain occurs when warm air is forced to rise. As the warm air rises it cools. Cold air cannot hold as much water vapour as warm air, so condensation occurs. Clouds are formed and rain occurs.

• There are 3 different types of rain, because there are 3 different reasons why warm air is forced to rise.

1. Relief rainfall2. Frontal (cyclonic) rainfall3. Convectional rainfall

Relief Rainfall• Relief rainfall occurs when;

- Warm moist air moves in from the sea.- It hits a mountain range at the coast and is forced to rise.- It cools as it rises.- Condensation occurs, clouds form and it starts to rain.

Frontal Rainfall• Frontal rainfall occurs when;

– Warm and cold air masses meet at a Front– The warm air mass moves up over the cold air mass.– The warm air cools and condensation takes place.– Stratus clouds form and rain occurs.

Convectional Rainfall• Convectional rain occurs when;

– The sun shines on the land and heats up the air above it.– The heated air rises quickly.– As it rises it cools and condensation occurs.– Cumulus clouds are formed and heavy rain occurs.

The Weather• When we talk about the weather we usually talk about the

following things.

1. Temperature2. Precipitation (rain etc)3. Sunshine4. Wind speed5. Wind direction6. Atmospheric pressure7. Humidity

All of these different aspects of the weather can be measured.There are different weather instruments to measure each thing. These instruments are usually in a weather station.

Temperature• Temperature is

measured using a Thermometer.

• It is measured in degrees Celsius (°C).

• Lines on a weather map showing areas of equal temperature are called Isotherms.

Temperature• You need to know how to calculate the;

1. Mean Temperature 2. Temperature Range

Mean Temperature: Add all the monthly temperatures, then divide by 12.

Temperature Range: Take the lowest temperature away from the highest temperature.

Mon Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec

MeanMonthly Temp

10 13 15 17 18 21 23 28 21 15 12 11

Precipitation• Precipitation is

measured using a Rain Gauge.

• It is measured in millimetres.

• Lines on a map showing areas of equal precipitation are called Isohyets.

Sunshine• Sunshine is measured

using a Campbell Stokes sunshine recorder.

• Sunshine is measured in Hours per day.

• Lines on a weather map showing areas of equal sunshine are called Isohels.

Wind• We can measure 3 things about the wind.

• Wind Speed – Using an Anemometer.• Wind Direction – Using a Wind Vane.• Wind Strength – Using the Beaufort Scale

The Beaufort Scale

• The Beaufort Scale describes the effect the wind has on the landscape.

• Wind strength is divided into 12 forces.

• The Beaufort Scale was invented by an Irishman.

Atmospheric Pressure• Atmospheric pressure

is measured using a Barometer.

• It is measured in millibars.

• Lines on a weather map showing areas of equal pressure are called Isobars.

A Barograph can also be used to measure atmospheric pressure

• What is Humidity?Humidity is the amount of moisture in the air. It can be measured in various

ways, but the most usual is to describe it as 'relative' humidity. This is

expressed as a percentage. A relative humidity of 100% means the moisture

content of the air is the maximum possible at any particular temperature. The hotter the air, the more moisture it

can hold.

Humidity• Humidity is measured

using a Hygrometer.

• A common type of hygrometer is a wet and dry bulb thermometer.

• It is expressed as a %. 100% is the maximum.

What you have learnt1. Weather associated with high and low

pressure. 2. Fronts3. Reading weather charts4. Water cycle5. Rainfall6. Measuring weather