2. Weather
The weather is all around us, all the time. It is an
important part of our lives and one that we cannot
control. Instead the weather often controls how and
where we live, what we do, what we wear and what we
eat. Someone who studies the weather is called a
meteorologist. Weather predictions are made by
forecasters who you see on television.
What is weather???
Weather is the day-to-day conditions of a particular
place.
3. Forecasting
weather
On television and radio, we often hear weather
forecasts predicting the weather. They are not fortune
tellers but base their reports on the collection of a large
amount of scientific information. Satellites have been put
into orbit around the earth to measure the amount of
heat from the sun. We can see pictures from the
satellites on the television. All these observations are
used to produce the weather forecast.
Weather forecasting is one of those rare activities that
unite nations in a common effort from which people
world wide benefit. Through weather satellites and
combined effort of more than 180 countries of the World
Meteorological Organization, we can track the forces that
control our weather and forecast their behavior up to a
4. Climate
Climate is often spoken about at the same time as
weather, but it is something quite different. The climate is
the common, average weather conditions at a particular
place over a long period of time (for example, more than
30 years). We learn about different climates around the
world. Deserts have a hot and dry climate while the
Antarctic has a very cold and dry climate.
5. Weather
There are number of important elements of weather that
have to be measured and recorded hourly or daily.
1.Temperature
2. Wind
3. Cloud
4. Sunshine
5. Visibility
6. Humidity
7. Pressure
8. Precipitation
6. Temperature
Temperature is the measure of how cold
or hot somewhere is. Temperature is
usually higher during the day than at night.
Rural areas (the countryside) are often
cooler than towns and cities. This is
because there are more buildings and
factories ( known as 'heat islands') which
absorb heat during the day, releasing it
slowly at night and warming the
surrounding air.
7. Wind
The earth’s atmosphere and air around us is
always moving. Wind is simply moving air.
Sometimes it moves slowly creating a gentle
breeze. Other times it can move faster creating
stronger, more powerful winds. We cannot see
the wind, but we can see what it does to trees
outside and kites on the beach. If you are
outside on a windy day you can sometimes feel
the wind on your face. It may be so windy that it
is difficult to walk.Both the direction and speed of
the wind should be measured for weather
observations.
8. Cloud
Clouds are made up of millions of tiny
water droplets. Clouds are made when
quite warm, moist air rises into the sky
where it cools down and condenses.
Clouds can form in a few minutes or over
a number of hours. There are many
different types of cloud and looking at
them can help you to predict the weather.
9. Sunshine
The amount of sunshine we have
depends on latitude and how much cloud
there is in the sky. In some of the world's
deserts the number of sunshine hours is
very high, more than 3,600 hours each
year. In the Eastern Sahara desert, the
sun is covered by clouds for less than 100
hours a year. In Britain we have from
1,850 hours in Southern England to 1,200
hours in North Scotland. There is usually
10. Visibility
We have all seen a foggy day when it is difficult to
see, and no matter how fast you run the fog
seems just as thick and just as far away from you.
This is because there is no insulating blanket of air
above to keep the earth's heat in. The air closest
to the ground cools rapidly, with all the water
vapour in the air condensing as tiny floating
droplets of water.
Visibility is simply how far you can see. In
weather terms it is how clear the atmosphere and
air are, taking into account fog, mist and urban
pollution. Fog and mist are like clouds on the
ground. They are made up of lots of tiny water
droplets, which is why you can sometimes get wet
11. Humidity
Humidity is how much water vapour is in
the atmosphere. Like a sponge, the air is
always evaporating and storing water from
rivers, lakes and oceans. In tropical parts
of the world, warm air is able to hold more
water vapour and humidity is higher as a
result.
12. Pressure
Pressure is the weight of the atmosphere
on the earth’s surface. This atmospheric
pressure is lower at the top of mountains
and highest at sea level. This is beacuse
all the air above the sea pushes down on
its' surface. Rapid drops in air pressure
mean unstable conditions and a storm is
on its way, while rises in pressure mean
conditions are more stable and fair
weather is returning.
13. Precipitation
Precipitation is the release of water from
the atmosphere to the earth’s surface as a
solid or liquid. It includes rain, snow, hail,
sleet and dew.
RAIN
In the British Isles, rainfall is a very common
type of weather. Rain starts above us when
small droplets of water in the clouds join
together until they get too big and heavy and fall
from the clouds. However, different cloud types
can produce different rainfall. Heavy rainfall after
a hot summer day may fall from tall, large white,
14. Precipitation
SNOW
During the winter months when
temperatures are cold, (at or close to 0º
Celsius) snow will fall from clouds instead
of rain. Snow starts off in the same way as
rain, with tiny droplets of water joining
together in clouds until they are too heavy.
However, when they fall it is important that
the air is freezing for there to be snow.
Otherwise the snowflakes will melt and
become sleet or rain before they reach the
15. Precipitation
HAIL
Hail falls as hailstones, which are like
small balls of ice. Their diameter usually
ranges from under a centimetre to 5cm.
Larger hailstones can cause damage to
crops and gardens, greenhouses and
glass roofs
16. Measuring instruments of
weather
Why are they needed?
Measuring instruments of weather are
needed to measure different kinds of
weather conditions accurately. There are
many different types of instruments for
measuring weather like-
Thermometers, barometers, anemometer,
rain gauge, scales etc
17. Temperature
Temperature is measured using a
thermometer, with units in degrees on
Fahrenheit (ºF) or Celsius (ºC) scales. The
main type of thermometer used is the
liquid-in-glass thermometer. A liquid
(usually alcohol) expands depending on
temperature. It then moves up a small tube
alongside a scale, from which temperature
readings can be made. Thermometers
should be put within a Stevenson Screen
to stop temperature readings being
affected by direct sunlight.
18. Wind
Wind Direction
One of the oldest pieces of equipment used to
measure weather is a wind vane. This wind or
weather vane is usually made from a strong
material, (like metal) and placed above ground,
usually on top of a building. The wind vane will
show clearly the 4 principle directions of the
compass: North, East, South and West, and have
a moveable arm that can point in any direction.
Once true north is known (using a compass), the
wind direction can be found by looking at the
direction the arm is pointing from. For example, air
moving from east to west will create an easterly
wind.
19. Wind
Wind speed
The wind speed is measured using an
anemometer. Most weather stations
measure wind speed using a spinning cup
anemometer, which rotates depending on
the wind.
20. Cloud
Cloud can be measured through a number of
observations. Consider whether the cloud is:
HIGH
(5,500-14,000 meters)
Includes: Cirrus, cirrocumulus, and cirrostratus
MEDIUM
(2,000-7,000 meters)
Includes: Altocumulus, altostratus, and nimbostratus
LOW
(below 2,000 meters)
Includes: Stratocumulus, Stratus, Cumulus, and
Cumulonimbus
21. Cloud
Altitude Name Color Descripti Weather
on
High Thin silky
Cirrus White and Fair
feathery
High Cirrocumulu Ripples/bu
White Fair
s mps
High Fat, smooth
Cirrostratus Whitish transparent Worsening
sheet
Medium Layers and
waves often
Altocumulus White/grey Fair
separated
by blue sky
22. Cloud
Altitude Name Color Descripti Weather
on
Low Layers in
Stratocum Grey/whit rounded
Dry/dull
ulus e rolls. No
breaks.
Low Thin
sheet
Stratus Grey Drizzle
blanketing
sky
Low Grey/whit Puffy
Cumulus Good
e clouds
Low Storms.
23. Cloud
The cloud types above are the most common in
the UK, though more unusual clouds may
sometimes be seen. In May 2004, mammoths
cloud was visible at the base of a cumulonimbus
formation over Broad Oak Nature Reserve.
The amount of cloud in the sky is measured in
eighths (or okras by meteorologists). Simple
observation can be made such as
Clear - no cloud cover
Partly cloudy - less than half cloud cover
Mainly cloudy - more than half cloud cover but
with some breaks in the cloud
Overcast - complete cloud cover
24. Sunshine
Hours of sunshine are usually recorded
on a simple machine called a
pyrheliometer. also known as a Campbell-
Stokes recorder. It works by using a glass
ball to focus the sunlight and rays onto a
strip of card. As the sun moves round
during the day, the card is scorched
creating a record of how many sunshine
hours there were.
25. Visibility
Visibility can be estimated using descriptive words such as:
good, poor, foggy etc. How far you can see is also used to
describe visibility:
Fog – less than 1km
Poor – 1 to 5km
Moderate – 5 to 10km
Good – more than 10km
Different environments around the world experience
different levels of fog. People living high in the mountains
may see fog all year. The city of San Francisco in North
America is famous for its thick mist that moves in from the
Pacific Ocean. In the United Kingdom we mainly see fog in
autumn and winter, but some tropical parts of the world
may never have seen fog.
There are two types of fog. Click to find out more:
1. Advection Fog
2. Radiation Fog
26. Fog
Advection Fog
Forms when quite warm, moist and stable air is
blown across a cooler surface (land or water). The
air temperature falls until the dew point is reached
and condensation occurs.
Examples of advection fog include San Francisco.
Radiation Fog
This type of fog is a thin layer that forms because
land cools down overnight. When the dew point is
reached and condensation occurs, the fog moves
slowly upwards. Radiation fog is common at lakes,
harbours and in river valleys.
27. Humidity
Relative humidity is a measure of how
much water vapour is actually in the air
compared to how much water vapour the
air could hold. This is measured using a
wet and dry hygrometer. This type of
thermometer has two bulbs; one is kept
wet in distilled water and the other dry. The
difference in temperature between them
can be calculated to give relative humidity.
Humidity must be high for fog or clouds to
29. Precipitation
Rain
It is useful to measure the amount of
rainfall we have, as it provides an
important source of water to reservoirs
giving us drinking water. Rainfall is easy to
measure by recording how much water
collects in a rain gauge. The rain gauge is
quite accurate as long as it is set up safely
at ground level in an exposed place. The
amount of rainfall collected in the gauge is
measured in millimetres. Rainfall data can
be used to work out monthly averages and
30. Precipitation
Snow
Snow cannot be measured in the same way as
rain, as a normal rain gauge may get blocked.
Instead, the amount of snowfall is measured
by inserting a ruler into a layer of snow that is
flat and has not been drifted by the wind.
31. Measuring instruments of
weather
So, these are the different types of
Measuring instruments of weather that I
explained you about. Hope you enjoyed
the ppt as much as I enjoyed making it.
