British weather, climate and cloud types.

-British Climate and weather-

Britain has a mild climate. It is in the temperate climatic zone and the sea affects the weather. In general, this means that Britain gets cool, wet winters and warm, wet summers. The weather conditions are also very changeable. Prevailing winds are the dominant wind direction in an area. The temperature of the wind and the amount of rainfall partly depend on where the air has come from. Looking at where the air has come from helps to explain the characteristics of the weather. A large body of air with similar characteristics is called an air mass. Locations that are further north receive less concentrated energy from the Sun. The equator lies directly underneath the Sun and so countries that fall on the equator receive the strongest solar energy. This means that in the Northern Hemisphere, the Sun's energy becomes less concentrated and therefore the temperatures become cooler as you travel north. Temperatures decrease with altitude. There is a 1°C drop in temperature for every increase of 100 m in height. This is because the air is less dense in higher altitudes. Distance from the sea. Coastal areas are most affected by the sea. The sea takes longer to heat up and cool down than land. So in the winter the sea keeps coastal areas warm and in summer, it cools them down. The effect that ocean currents have on the temperature depends on whether the ocean current is hot or cold. Britain is on the same latitude as Siberia and parts of Russia, yet it does not suffer the same long, harsh winters. Britain's mild climate is partly due to the Gulf Stream, a large Atlantic Ocean current of warm water from the Gulf of Mexico. When the land warms up, it heats the air above it. This causes the air to expand and rise. As the air rises it cools and condenses. If this process continues then rain will fall. This type of rainfall is very common in tropical areas but also in areas such as South East England during warm sunny spells. The British Isles are affected by a number of different air masses. When warm and cold air meet, a depression forms.

-Climate and Weather-

Weather describes the day-to-day conditions of the atmosphere. Weather can change quickly - one day it can be dry and sunny and the next day it may rain. Climate describes average weather conditions over longer periods and over large areas. The table below shows the world climatic zones.Weather affects us in many ways. It affects what we do and what we wear, how we travel and even our moods. Meteorologists measure weather conditions in different places and use this information to report and make forecasts about future weather conditions. This is useful because people can be warned about hazardous weather conditions such as storms and floods. Temperature is measured in Celsius (°C) using a thermometer. The thermometer must be shaded from direct sunlight and should have air circulating around it. The thermometers can be placed in a Stevenson Screen. This is a wooden box with slatted sides, a sloping roof and legs to keep the screen off the ground. It is painted white to reflect the sun. Precipitation is measured using a rain gauge. This is a funnel inside a graduated container. The depth of the rain in millimeters can be read from the side of the container. Wind direction is reported by the direction it is blowing from, according to the compass. Wind blowing from the west is travelling eastwards so is called a westerly wind, not an easterly wind. Wind speed can be measured using an anemometer. The strength of the wind is measured on the Beaufort scale.

-Type of Clouds-

Cloud cover is measured in units called oktas. Each okta represents one eighth of the sky covered by cloud. Air pressure. Air is light but because there is so much of it above us, it exerts a pressure on us. Air pressure is measured by a barometer. The units used are millibars. The greater the reading, the higher the pressure. A high-pressure system is called an anticyclone. Air falls in an anticyclone so no clouds are formed. In summer, high pressure usually results in clear skies, gentle breezes and fine weather. In winter high pressure leads to clear skies and colder conditions. An area of low pressure is called a depression. Air rises in a depression so clouds and rainfall are formed. Depressions therefore bring unsettled weather and rain. Winds are normally stronger. They usually form over the Atlantic Ocean and are carried across Britain by westerly winds. A synoptic chart is any map that summarize atmospheric conditions over a wide area at a given time. It displays information on temperature, precipitation, wind speed and direction, atmospheric pressure and cloud coverage, all observed from many different weather stations, aeroplanes, balloons and satellites. Clouds are categorised according to height and shape. The different categories of clouds are then given names based on Latin words, eg nimbus clouds bring rain, stratus clouds appear as layers.