Blog de sociales Abraham Jesús Fernández: UNIT 4. THE ATMOSPHERE.

1. ATMOSPHERIC PHENOMENA. WEATHER AND CLIMATE.

We have to distinguish between the atmospheric weather an the climate.

Atmospheric weather is the state of the atmosphere over one place at a specific time. The weather is changeable and can be different every day. This is because the troposphere is divide into large air masses that are moving continuously over the Earth's surface.

The science that study the weather is meteorology.

Heatwave in London.

Snowfall in Jerusalem.

The climate is the average state of the atmosphere over one place during a long period of time. It is calculated observing the succession of types of weather for at least thirty years. Is more stable than weather.

The science that study the various types of climate is climatology.

ACTIVITIES:

You can find the solutions here.

1. Indicate which of these phrases refers to weather and which to climate.

a). The summers in Madrid are very hot and almost without precipitations.

b). The evening was cloudy and windy in London yesterday.

c). Weather is always hot and rainy in Indonesia.

d). This June has been hotter than usual in Seville.

e). They said that winters are very cold in Bergen.

f). Last week was raining all the time in Barcelone.

2. SOLAR RADIATION AND TEMPERATURE.

The Sun is the source of most of the energy on our planet.

2. 1. Solar radiation.

Solar radiation is the solar energy that reaches the Earth surface. It is a continuous and unending energy source and explain the changes in the atmosphere. It has different components:

infrared rays.
visible light.
ultraviolet A
ultraviolet B

Solar energy is a rich and natural energy source and can have different effects:

beneficial: human health (sunny days and hig temperatures allow are perfect for outdoors temperatures), domestic energy, agriculture and industry (tourism)
harmful: continuous exposition can produce skin and eye diseases. The ozone layer and taning protect us from dangerous solar protection.

2. 2. Atmospheric temperatures.

Atmospheric temperature is the heating of air temperature as a result of solar radiation.
To measure temperature we use a device calle thermometer and is measured in degrees centigrade (ºC).
The Sun's rays are converted into heat when they touch the Earth's surface. This heat is transmitted to the surrounding air.
Air temperature make people fell warm and cold and high and low temperatures influence how people equip their homes, plan activities and developed economic activities.
Temperatures varies, because of that, we have to distinguish between:

Maximum temperature: the highest temperature on a specific day, year or period of years.
Minimum temperature: the lowest temperature on a specific day, year or period of years.

3. AIR HUMIDITY AND PRECIPITATION.

The temperature of the air determines how much water vapour it can absorb. Hot air absorb more water than cold air.

Air humidity.

Humidity is the amount of water vapour in the air.
It is meassured with an hygometer and is expressed as a percentage. A 100% humidity means the air is saturated and cannot absorb more water vapour.

Precipitation.

Water vapour cools at high altitudes and it condenses into droplets that accumulate and form clouds. These droplets can change into ice crystals if the coold down a lot and remain suspended because they are small and light.
If the air continues to rise, the droplets became bigger an heavier and start to fall as precipitation. There are different types of precipitation:

Rain (in spanish lluvia), water drops bigger than 0.5 mm.
Fog, (in spanish niebla) small water drops which remain near the surface and reduce visibility.
Snow (in spanish nieve), small ice crystals. When appears combined to strongs winds is called blizzard.
Dew (in spanish rocio), droplets which appear when water vapour make contact with cool surfaces.
Frost (in spanish escarcha) a thin layer of ice formed when water vapour freezes.
Hail (in spanish granizo), irregular shaped balls of ice, ranging from 5 to 50 mm.

4. ATMOSPHERIC PRESSURE AND THE WIND.

Atmospheric pressure and its factors.

Definition.

Atmospheric pressure is the weight of a column of air on a place. It is meassured with a barometer and is expressed as millibars (mb).

The average atmospheric pressure meassured at sea level it is 1.013 mb, but the atmospheric pressure changes and it is higher or lower in different areas because of two factors:

altitude, the higher the altitude, the smaller the volume and weight of the column of air over a location becomes.

air temperature:

cold air is denser and heavier, so its tends to fall. As a consequence, its warmed and produces dry and estable weather, and zones of high pressure known as anticyclones
warm air is lighter and less dense, so it tends to rise, then cools and produces precipitation. As a consequence produces zones of low pressure known as depressions.

Weather maps.

A weather map is a chart that represent meteorological conditions over a specific area at a specific time. In a weather map appear the following elements:

isobars, lines that connect all the points of equal atmospheric pressure.
anticyclones are represented with a capital A (usually are also represented with an H, high pressure). The wind moves between the isobars from left to right in the northern hemisphere and from right to left in the southern hemisphere.
depressions are represented with a capital B (usually are also represented with an L, low pressure). The wind moves between the isobars from rigth to left in the northern hemisphere and from left to right in the southern hemisphere.

fronts, areas of contact between two air massess with different characteristics. Can be:

hot fronts, represented with a red line with semicircles.
cold fronts, represented with a blue line with triangles.
Occluded front, represented with a red line with semicircles and triangles (is the meeting of a hot and a cold front). In this case, the front is about to dissapear.

Weather map.

Wind and its factors.

Wind is the horizontal movement of air. Is caused by the difference in atmospheric pressure. The wind blows from areas of high pressure towards areas of low pressure.

Measurement:

its speed is measured in kilometres per hour (km/h) or in metres per second (m/s), using a anemometer.
its direction is determined by the cardinal point of the source of the wind: east wind, north wind. Is measured using a weather vane.

Weather vane.

On Earth we are going to find:

Prevailing winds are constant all the year around and always blow in the same direction. The most important are the trade winds (in spanish: alisios) which goes from the Tropics to the Equator, the west winds and the polar winds.
seasonal winds, change direction depending on the season, such as the monsoons (in spanish: monzones) in South East Asia
Local winds, affect small geographical areas such as marine and mountains breezes (in spanish: brisas).