Category Weather

WHAT IS CARBONATION?

Decaying leaves and plant matter give out carbon dioxide, which is also present in the air around us. Carbon dioxide dissolves in water to create carbonic acid through a process called carbonation. This acid can, over time, dissolve rocks, especially limestone. Limestone is a soft rock that consists mainly of calcium carbonate, which reacts with rainwater, dissolving away to create huge caves and cave complexes.

Carbonation is the chemical reaction between carbon dioxide present in the air, and the hydration compounds of the cement in concrete structures. The rate of carbonation depends on the physical characteristics such as the design, on-site preparation, production and protection, as well as external factors, such as the location and degree of exposure to contaminants and other environmental factors. Carbonation may lead to the corrosion of the reinforcement steel and deterioration of concrete structures.

The carbonation process starts immediately when concrete is exposed to air. Carbon dioxide (CO2) penetrates the concrete through the pores where it reacts with the calcium hydroxide and the moisture in the pores to form calcium carbonate. The carbon dioxide combines with the pore water to form a dilute carbolic acid which acts to reduce the concrete’s alkalinity.

Carbonation reduces the concrete’s natural alkalinity from pH13 to about pH8. Whereas a high pH provides a passivation layer around the steel, at pH below 9.5, the passivation layer breaks down and exposes the reinforcement steel to the corrosive effects of water and air.

When steel rusts, it expands in volume and exerts force on the surrounding concrete, causing the concrete to crack and spall at a rate that increases exponentially if the corrosion is not prevented.

Credit: Corrosionpedia

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What is Climatology?

Climatology is the study of the atmosphere and weather patterns over time. This field of science focuses on recording and analyzing weather patterns throughout the world and understanding the atmospheric conditions that cause them. It is sometimes confused with meteorology, which is the study of weather and weather forecasting. However, climatology is mainly focused on the natural and artificial forces that influence long-term weather patterns. Scientists who specialize in this field are called climatologists.

The first studies of climate can be traced back to ancient Greece, but climate science as it is now known did not emerge until the advent of the industrial age in the nineteenth century. The science of climatology grew as scientists became interested in understanding weather patterns. In recent times, climatologists have increasingly focused their research on the changes in Earth’s climate that have occurred since the industrial age. Earth has been growing warmer and warmer as human industry has expanded and released more carbon into the atmosphere. This effect, called global warming, is a particularly important object of study for climatologists. By studying global warming, climatologists can better understand and predict the long-term impact of human-caused climate change.

Credit: National Geographic Society

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What creates different weather conditions?

The weather depends on the way the air moves (wind), the moisture if carries (humidity), and its temperature (warmth). These are controlled by changes in air pressure. As air heats up, it becomes thinner and lighter. It rises upwards, creating an area of low pressure beneath it, which pulls in air from around to fill the empty space. As the air rises, it cools, forming clouds. But the cooler the air gets, the denser and heavier it becomes until eventually it starts to sink. The high pressure created pushes air down towards the ground, causing it to fan out and blow away everything in its way, stopping   the formation of clouds. This is why clear blue skies occur on high air-pressure days.

Weather comes in all different forms, and it changes by the day. It could be sunny one day and raining the next. It could even be sunny, rainy, cloudy, and stormy in one day.

Temperature

It’s getting hot out there. When you talk about the heat of the air outside on a summer day, this is the temperature. Measured with a thermometer in Fahrenheit, Celsius, or Kelvin, the temperature tells you how fast the air molecules and atoms are moving. Fast-moving molecules and atoms mean the temperature is high, while slow-moving molecules in the air create a low temperature.

Humidity

The moisture or dryness of the air is humidity. It’s an important weather aspect. Without it, humans wouldn’t be able to survive. However, the amount of water vapor, or humidity, in the air needs to have balance. Too little or too much water vapor in the air causes health issues and can be dangerous.

Precipitation

Precipitation is just a big word to describe how water falls to the ground. It can be rain, snow, sleet, ice, hail, or drizzle. The form these water or solid particles take depends on other weather factors. For example, if the temperature is cold, below 32 degrees, precipitation comes to the surface in the form of snow. If the weather is nice and warm, water comes down in the form of rain.

Wind

Air moves. All you must do is walk out your door to feel that. The movement of air is created by how the sun heats the Earth, and then convection tells you how air moves in predictable patterns. Therefore, meteorologists have some idea of how a storm will move or the type of weather you’ll have in a week.

Credit: Your Dictionary

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What is Weather?

Weather

Somewhere on the earth right now, it is cloudy and rainy. Somewhere it is sunny. Somewhere it is dark, windy, and snowing.

What is the weather like today where you are? Is it raining? Does it look as if it’s about to snow? Is the sun shining?

Do you ever talk about the weather? Many people do. Almost everyone cares about the weather.

The weather affects us in many ways. Day-to-day changes in weather can influence how we feel and the way we look at the world. Severe weather, such as tornadoes, hurricanes, and blizzards, can disrupt many people’s lives because of the destruction they cause.

Weather doesn’t just stay in one place. It moves, and changes from hour to hour or day to day. Over many years, certain conditions become familiar weather in an area. The average weather in a specific region, as well as its variations and extremes over many years, is called climate.

There are six main components, or parts, of weather. They are temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness. Together, these components describe the weather at any given time. These changing components, along with the knowledge of atmospheric processes, help meteorologists – scientists who study weather – forecast what the weather will be in the near future.

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How can scientists control the weather?

            Since the 1940s scientists have discovered techniques by which. Several weather conditions can be controlled. For example, it is pos­sible’ to prevent lightning by using an electrical earth to diffuse the electrical content of a cloud. The American scientist V. J. Schaefer has shown .that it is feasible to produce greater concentrations of ice in clouds than occur under normal conditions.

            Weather experts already are taking advantage of these dis­coveries to increase snowfall on mountains for winter sports, to prevent damaging hailstones and to moderate, or even prevent, the development of dangerous storms. Scientists are now able, in some cases, to make a cloud burst to produce rainfall over parched areas.

            These local efforts may lead the way to large-scale weather con­trol. But before then scientists may’ have to learn to cope with the damaging effect of air pollu­tion on weather conditions.

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Climate Extremes

 

 

Can sand dunes move?

Sand dunes can move slowly, causing deserts to spread over more fertile land. Continuous winds blow the sand to form crescent-shaped dunes. Sand from the top of the dune is blown farther away, and it gradually collects to form a new dune.

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How can people live in extreme climates?

Over millions of years, the human body has altered to suit the climate of the regions we inhabit. In general the hotter the region, the darker the skin of its inhabitants. Also, many people from Asia have a fold of skin in their eyelid to protect them from strong sunlight. People living in hot climates do not need a fat layer to keep warm, so they are usually slim. The Inuits of the Arctic, however, are mostly shorter and stockier to help conserve heat. 

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Which are the wettest places on the Earth?

Tropical rainforests are among the wettest places in the world. In general, most rainfall occurs on the sides of hills and mountains. The wettest place of all is Cherrapunji, in Assam, India. It faces the full force of the monsoon winds that sweep in from the Indian Ocean in July. Their warm, damp air rises in the Himalayan foothills, causing torrential rain. Mount Wai-‘ale-‘ale in Hawaii has the wet days each year. It rains on 350 days on average, and the annual rainfall is the highest recorded anywhere.

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Climate Extremes

 

What is permafrost?

Permafrost is a layer of ice and frozen soil that never thaws. It lies beneath nearly one-quarter of the Earth’s surface, throughout Alaska, Canada and Russia. Sometimes the soil in these places is frozen to a depth of up to 1,500 m. The surface layers may melt enough in summer for plants to grow, but the soil beneath is permanently frozen.

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Are there places where nothing can live?

Hot volcanic lava is probably the only place on the Earth’s surface where there is no life at all. Living things have evolved to survive in the harshest environments. Tiny bacteria can be found everywhere on the Earth, even buried in thick ice at the poles or in the very deepest parts of the ocean. 

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Climate Extremes

 

 

Where are the most extreme temperatures found?

Libya and the Antarctic have recorded the most extreme temperatures. The hottest shade temperature was in Libya in 1922, when the temperature in the Sahara desert reached 58 °C. Temperatures nearly as high as this were recorded in Death Valley in the USA in 1913. The coldest ever recorded temperature was in Antarctica in 1983, when Russian scientists measured a temperature low of – 89.2°C.

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The desert process

Deserts were once green and fertile areas, until a climate change altered them permanently. Just a small reduction in rainfall causes plants to die off. Without plant roots to bind and nourish the soil, the land gradually becomes barren. Soon the animals move away, and only desert remains. Very few deserts are completely barren, and plants and animals have evolved to live in the driest conditions, conserving their body water so they do not need to rely on rainfall.

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Climate Extremes

 

Are there cold deserts?

Antarctica is the biggest cold desert in the world. All of its water is locked up in ice and snow, so nothing can grow. The Gobi desert in Mongolia and western China is also very cold in the winter, when temperatures drop below freezing. However, it is hot in the summer.

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What is a mirage?

Mirages form in hot deserts, where the air is so hot it bends and distorts light rays. The shimmering images that a mirage produces have often tricked travellers in deserts. People think that they can see a town or oasis on the horizon, but in reality there is none. 

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Climate Extremes

Where is the world’s driest place?

The world’s driest place is the Atacama Desert in Chile. It is a narrow strip between the Andes and the Pacific, where the first rain for 400 years fell in 1971. Like other hot deserts, the Atacama lies in a region where air pressure is constantly high, with little air movement or cloud. Rainfall is very low in other deserts. Near Cairo, Egypt, annual rainfall averages about 28 mm each year, while in Bahrain, on the edge of the Arabian Desert, there is as much as 81 mm of rainfall. The rain may come in a single heavy storm, and some years there is no rainfall at all. 

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How much of the world is covered by desert?

About one-third of the world’s land surface is covered by desert. Desserts are found wherever there is too little water to allow much plant life to grow. This lack of vegetation leaves large areas of soil exposed. The largest desert in the world is the Sahara in Africa. It has an area of about 9 million sq km. 

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INTRODUCTION – WEATHER

An understanding of the weather is often vital to daily life – framers, for example, require information about the weather to try and protect their crops. Extremes of weather can ruin entire crops.

Sometimes even our safety depends on knowing about weather conditions. With advance warning of a major storm, ships or aeroplanes can be routed away from danger. Flood warnings can be issued and people moved to a safe area.

Farmers need to irrigate, or water, their crops if there is no rain.

Heavy rain can cause rivers to burst their banks and flood large areas of land.

THE WEATHER

When we say “The Sun is shining”, we are talking about the weather. However, when we say “It’s always sunny here”, we are talking about the climate. The climate describes the way weather behaves over many years. The climate depends on many factors, including how far from the equator a place is. Weather is caused by changes in the ‘atmosphere’ – the layer of air surrounding the Earth.

Generally, weather and climate are caused by parts of the world becoming warmer than others when the Sun’s rays heat the Earth’s surface. These differences in temperature make the air move and these air movements cause the different types of weather we know.

The changing weather – hot, sunny conditions in summer heavy snow in winter. Some parts of the world get hurricanes – very strong winds.

THE WIND

Winds carry warm and cold air around the world. Knowing which way the wind is blowing is a useful guide to the type of weather we can expect. Around the world, there are many differences in temperature. Air in contact with hot land or sea is warmed. As warm air is lighter than cooler air, it rises. Cooler air then moves in to take its place. This movement of air is what we call wind.

Winds can be extremely powerful; they can knock down trees, and can push along boats fitted with sails. The map shows the routes of the main winds across the globe. These routes were once followed by sailing ships carrying their cargoes around the world.

 

Sea breezes

As the Sun shines, air over the land is heated more than air over the sea, and this hot air rises. Cooler air from over the sea moves in to take its place.

The hot air cools as it rises, but it does not fall straight back down. Instead, it spreads out over the sea and falls down there. This circular air current causes an onshore breeze.

 

 

 

 

The map shows the major winds of the world.

 

 

 

 

 

 

 

 

 

Yachts with the wind in their sails

CLOUDS

Clouds are formed from water vapour. The air collects this vapour as it passes over damp places, like the sea. We call the process of a liquid turning to gas ‘evaporation’. Normally, the vapour in the air is invisible, but if the air is cooled then clouds of tiny water droplets are formed. This process we call ‘condensation’.

The amount of water vapour that the air can carry depends on how hot the air is – warmer air can carry more moisture. When warm, moist air rises, either by moving over hills and mountains, or by meeting cooler air, it is cooled. As the air cools, it can carry less vapour. The excess moisture forms clouds of tiny droplets.

Storm clouds gathering

 

 

 

 

The fluffy, white clouds you see on fine, summer days are called ‘cumulus’.

 

 

 

 

 

 

 

Your breath

The way clouds form is like the way a misty cloud forms when you breathe out on a cold day. The air that you breathe out contains a lot of moisture. On a cold day, this air is cooled as it meets the cold air outside. As it cools, it can hold less water vapour, and the extra water forms tiny droplets, like a cloud. When a whale breathes out, the water vapour in its warm breath condenses into a misty spray.

RAIN AND SNOW

 

The tiny water droplets inside a cloud may bump into each other and join together to form larger droplets. If the air inside a cloud is rising, these droplets are lifted up again and join with others to form yet larger droplets. When the droplets are very large, about the size of raindrops, the rising air can no longer lift the drops back up and so they fall as rain.

 

 

 

 

 

 

 

The water cycle

The evaporation of water caused by sunshine makes the air moist. Moist air travelling inland may have to rise over hills and this cools it. As the rising air is cooled, clouds form and rain may fall. The rain falling on the land runs into streams, which flow into rivers. The river water eventually returns to the sea.

 

Continue reading “RAIN AND SNOW”

AIR PRESSURE

 

We usually think of air as being weightless, but in fact air is quite heavy. The air in a large classroom has the same weight as a small car! The air of the Earth’s atmosphere reaches upwards for several hundred kilometres. The effect of this is that the air at ground level presses on everything it surrounds.

The exact air pressure changes from day to day. Studying air pressure, and the way it is changing, helps to tell us how the weather will change in the next few hours and days. Usually, high pressure brings good weather whereas low pressure brings bad weather. A device called a ‘barometer’ measures air pressure and is used to predict the weather.

 

 

 

 

 

On this map you can see areas of high pressure (H) and low pressure (L).

 

 

 

 

 

 

 

The effects of air pressure

You can see an effect of air pressure with a washing-up liquid bottle. If you remove most of the air from inside the bottle, by sucking it, the bottle collapses. This is because the air around it pushes inwards. Normally the air inside balances this force. Simple barometers measure changes in pressure in a similar way.

 

 

 

 

 

 

 

 

Large swirls of cloud like this one often indicate areas of low air pressure.

WEATHER ON THE MOVE

Weather forecasting is partly done by looking at the movements of ‘fronts’ – regions where warm air meets cooler air. The warm air at a front rises over the cooler air. This cools the warm air and so rain often falls near fronts.

Where warm and cool air meets, the warm air may become partly surrounded by cooler air. As warm air causes lower pressure, this creates a low pressure area called a ‘depression’. When a depression moves over us, we can expect unsettled, rainy or stormy weather.

A high pressure region called an ‘anticyclone’ form where cool air is surrounded by warmer air. An anticyclone moves slowly and can mean a long period of dry or sunny weather.

 

 

 

Bad weather can make driving very dangerous.

 

 

 

 

 

 

Movement of fronts

The region where cold air pushes against a mass of warm air is called a ‘cold front’.

The cold air burrows under the warm air (1) causing it to rise, and so clouds and rain are formed in the rising air.

The cold front catches up with a warm front, where warm air moves into a region of colder air (2). Here, the warm air rises over the cold air, causing more clouds and rain.

Eventually the cold air on the left catches up with the cold air on the right, and the warm air is lifted above ground level (3).

Finally, the warm air disappears, and we just see a region of cool air moving over a region of colder air (4).

STORMY WEATHER

 

Sometimes the weather can be extremely violent. One of the most severe types of weather is a hurricane, which may happen near tropical oceans.

Another violent form of weather is a thunderstorm. Thunderstorms happen in extremely moist air, where the grey-black thundercloud stretches up several thousand metres. Inside a thundercloud there are fast air currents which cause ‘static electricity’, electric charge, to build up inside the cloud. Lightning and thunder occur when this electric charge leaps from cloud to cloud or to the ground. The fast air currents inside thunderclouds can hold up large raindrops and so produce very heavy rain.

 

 

 

Thunderstorms can cause bolts of lightning to jump from a cloud to the ground.

 

 

 

 

 

Inside a hurricane

In the centre of a hurricane, called the ‘eye’, there is very little wind. Around the eye, there are very strong winds spiralling round and upwards. Further out there are swirling regions of cloud, reaching perhaps 50 km across. These clouds produce torrential rain.

LOOKING AT THE CLIMATE

The most important factor that influences the climate of a place is its distance from the equator – the imaginary line around the centre of the Earth. Places further away from the equator are usually cooler than places that are nearer. This is because the Sun’s light is spread over a larger area towards the Earth’s poles and it has to travel through more of the atmosphere to get there.

 

Climate and the sea

Places far from the sea, or hidden from the sea by great mountain ranges, often have very little rainfall – the air reaching them has already lost most of its moisture as rain on its journey over the land.

Places near to the sea do not usually have great temperature changes. The sea heats up much more slowly than the land and cools more slowly. Therefore, it keeps the land warm in winter and cool in summer.

 

 

 

 

Deserts often have little rainfall because they are sheltered by mountain ranges.

 

 

 

 

 

 

 

 

The climate is affected by how high up you are and where in the world you are. As you go higher, the climate becomes cooler and eventually too cold for trees to grow. Even higher, the ground is covered by snow all year round. The ‘snow line’ and ‘tree line’ become lower as you move away from the equator.

The snow line and the tree line on the side of the mountain.

THE SEASONS

 

 

As the Earth spins on its axis, it orbits about the Sun. This means that at different times of year, different parts of the world directly face the Sun in the middle of the day. In January, places about 2,000 kilometres south of the equator have the hottest weather. In July, the hottest weather is about 2,000 kilometres north of the equator. This means that the warmest season in the northern parts of the world is during July and in the southern part during January.

Many climates further away from the equator have four seasons. The weather in winter is often too cold for most plants to grow, and there is a good deal of frost. In summer and winter the weather is often stable for longer periods of time. The weather in spring and autumn often changes from day to day, with high winds and sudden showers. The main season of growth is spring.

 

 

 

 

As the hottest regions change, the directions of winds and positions of fronts change around the world. These winds and fronts affect rainfall, and so some regions have distinct rainy and dry seasons. In India, for example, there is a very rainy summer season, called the wet ‘monsoon’, but little or no rain from December to April.

The wet monsoon often causes flooding.

RECORDING WEATHER

 

Around the world, weather stations record the type of weather every day – they monitor the temperature continuously, the amount of rainfall and the hours of sunshine. Air pressure, which affects the weather, is also recorded. Measuring the ‘humidity’, or amount of moisture in the air, helps to predict clouds, fog or rain.

Satellites can be used in long-range weather forecasting – predicting the weather for a period of weeks. They orbit the Earth photographing it and recording weather patterns. Information sent back to the Earth could include warnings of a fast-developing storm in the tropics, or of a sudden snow melt in a mountainous region.

 

 

 

 

Recording sunshine

A sunshine recorder uses a large round lens to focus the Sun’s rays and burn a mark onto a piece of card. As the Sun moves across the sky, the burn mark leaves a trail showing how long the Sun has been shining.

 

 

 

 

 

 

The weather satellite Tiros orbits the Earth recording the weather.

WEATHER FORECASTS

Most people like to know in advance what the weather will be like. Weather forecasters often look for signs of fronts approaching – as a warm front approaches, the air pressure decreases and as a cold front approaches the air pressure increases. These changes in pressure often bring rain. A steady area of high pressure often says we can expect dry weather, cold in winter, warm in summer. Professional weather forecasters may use radar to watch how the clouds are moving. Information can also be processed by a computer to show, for example, temperature differences.

 

 

 

Satellite images can show a storm developing.

 

 

 

 

 

 

 

Pine cones are also a tool for the amateur weather forecaster. When the air is moist, just before rainfall, pine cones close their scales. In dry weather, the scales open again.

 

 

 

 

 

 

Many well-known sayings help amateur weather forecasters to predict the weather. “Red sky at night, shepherds delight”, says that a red sunset will bring dry and warm weather.

MORE ABOUT CLOUDS

 

 

 

The fluffy, white clouds you see on fine, summer days are called ‘cumulus’ clouds. When these rise up to form dark ‘cumulo-nimbus’ thunderclouds, there is a good chance of a heavy shower or a thunderstorm.

‘Cirrus’ clouds are the thin, wispy clouds you sometimes see very high in the sky on dry days. They usually mean a front is arriving, so you can expect the weather to change. As a front moves nearer, the cloud gets lower, turning into ‘alto-stratus’ or small ‘alto-cumulus’. Tall heaps of alto-cumulus means there may be a storm. Lower down, grey ‘nimbo-stratus’ clouds often cause continuous rain. ‘Stratus’ clouds form as a low sheet and often cause fog.