Weather hazards and climate change Flashcards
What is the atmosphere?
The atmosphere is the layer of air surrounding the Earth’s surface which extends hundreds of kilometres high
What is weather and what is climate?
Weather is the short term day to day conditions of the atmosphere
while Climate is the long term average temperature and rainfall.
Which part of the atmosphere does weather take place in?
Troposphere
What and where is the Hadley cell and what are its effects?
The first cell is called the Hadley cell. At the equator, the ground is intensely heated by the sun. This causes the air to rise which creates a low-pressure zone on the Earth’s surface. As the air rises, it cools and forms thick cumulonimbus (storm) clouds. The air continues to rise up to the upper atmosphere, and the following then happens:
The air separates and starts to move both north and south towards the poles.
When it reaches about 30° north and south, the air cools and sinks towards the ground forming the subtropical high-pressure zone.
As the air sinks, it becomes warmer and drier. This creates an area of little cloud and low rainfall, where deserts are found.
The Hadley cell is then complete. The air completes the cycle and flows back towards the equator as the trade winds.
In the northern hemisphere, the winds flow to the right and are called northeast trade winds. In the southern hemisphere the winds flow to the left and are called the southeast trade winds. This is down to the Coriolis effect and friction.
What is the Coriolis effect and its impacts on the weather of the uk?
Apparent force, due to the spinning of the Earth, which deflects movement of particles and wind.
In the UK, which winds are blown from the south due to the Ferrell cell but the earth spins to the right causing the prevailing wind to hit the UK in a south-westerly direction.
What and where is the Ferrell cell?
The Ferrel cell occurs at higher latitudes (between 30 degrees and 60 degrees N and 30 degrees and 60 degrees S):
Air on the surface is pulled towards the poles, forming the warm south-westerly winds in the northern hemisphere and north-westerly winds in the southern hemisphere.
These winds pick up moisture as they travel over the oceans. At around 60 degrees N and 60 degrees S, they meet cold air, which has drifted from the poles.
The warmer air from the tropics is lighter than the dense, cold polar air and so it rises as the two air masses meet.
This uplift of air causes low pressure at the surface and the unstable weather conditions that are associated with the mid-latitude depressions. Much of our wet and windy weather in the UK is determined by this.
What is the polar cell and its effects?
At the poles, air is cooled and sinks towards the ground forming high pressure, this known as the Polar high. It then flows towards the lower latitudes. At about 60 degrees N and S, the cold polar air mixes with warmer tropical air and rises upwards, creating a zone of low pressure called the subpolar low. The boundary between the warm and cold air is called the polar front. It accounts for a great deal of the unstable weather experienced in these latitudes.
What are ocean currents?
Heat from the tropics can be transferred to the cold polar regions, by large-scale water movement within the oceans. Each ocean has its own circular pattern of currents. Heat is transferred by warm ocean currents, such as the North Atlantic Drift in the Atlantic Ocean, from low latitudes to high latitudes. Ocean currents are set in motion by the prevailing surface winds associated with the general atmospheric circulation. The direction of water movement is also deflected by the
Coriolis effect.
What is pressure and the difference between high and low pressure?
Pressure is measured in millibars. Standard pressure at sea level is 1013 millibars, but large areas of either high or low pressure can occur. Areas of high and low pressure are caused by rising and sinking air. As air warms, it rises, leading to low pressure at the surface. As air cools, it sinks leading to high pressure at the surface.Low pressure causes wet conditions and High pressure causes dry and clearer conditions.
What is relief rainfall and why is the west of the UK so wet?
Relief rainfall, also known as orographic rainfall, occurs in areas where land increases height. It is widespread on the west coast of the United Kingdom due to the prevailing weather coming from that direction.
Relief rainfall is formed when the air cools as it rises over relief features in the landscape such as hills or mountains. As the air rises, it cools, condenses and forms rain.
In the UK, prevailing winds from the west lead to air rising over upland areas like the Pennines. As a result, rainfall totals of over 1,600 mm per year occur in the west of the UK. The downwind or leeward slope receives a small amount of rainfall in comparison.
Stage 1.
Warm wet air is forced to rise over high land.
Stage 2.
As the air rises, it cools and condenses. Clouds form, and precipitation occurs.
Stage 3.
The drier air descends.
Stage 4.
As the air descends, it warms, meaning it can carry water moisture, so there is little rain on this side of the mountain. This area is known as a rain shadow.
What is the climate of the UK?
The UK has a temperate climate. In general, this means that Britain gets cool, wet winters and warm, wet summers. It rarely features the extremes of heat or cold, drought or wind that are common in other climates. The weather conditions are also very changeable.
Not all parts of the UK have the same climate. London, in the south-east of the UK, is a region characterised by a warm and dry climate in the summer and a cold and dry climate in the winter.
Cumbria, in the mountainous north-west of England, has generally cooler temperatures and more rainfall throughout the year.
What is a glacial and an interglacial?
A glacial is a period of cold while an interglacial is a period of warm?
What are the patterns of climate across the UK
The general pattern of the climate across the UK has four distinct regions:
south-east – cold winters, warm and dry summers
south-west – mild and very wet winters, warm and wet summers
north-west – mild winter, cool summers and heavy rain all year
north-east – cold winter, cool summers and steady rain all year
What is precipitation?
Precipitation is any form of moisture which falls to the earth. This includes rain, snow, hail and sleet.
Precipitation occurs when water vapour cools. When the air reaches saturation point (also known as condensation point and dew point) the water vapour condenses and forms tiny droplets of water. These tiny droplets of water from clouds.
Complex forces cause the water droplets to fall as rainfall.
All rain is the same. It happens as the result of warm, moist air being cooled, leading to condensation and in turn rain. The following examples show three different ways air is cooled causing rainfall.
What was the last major cold period?
The last major cold period was known as the Pleistocene. It started 2.6 million years ago and ended just 10,000 years ago. Since then, conditions have been warmer. This current warm phase is known as the Holocene. The Holocene and Pleistocene are part of the Quaternary Period of Earth’s history.
What are the different methods of collecting evidence of climate change?
Ice Cores:
Scientists often use
ice cores to detect changes in temperatures. When snow falls it traps air into the ice. When scientists take a core of ice it reveals the atmospheric gas concentrations at the time the snow fell. This is used to calculate temperature at that time. The ice can reveal the temperature of each year for the past 400,000 years. Scientists that study the ice cores say there is clear evidence that there has been a rapid increase in temperature in the past decades.
Thermometer readings:
Ongoing temperature recordings using thermometers have shown a clear warming of the Earth’s temperature over the past few decades. By using this data, scientists have found that the Earth’s average surface air temperature has increased by around 1°C since the year 1900. The period between 2013 and 2022 was the warmest 10-year period on record; 2016 and 2022 are the warmest years since records began. The degree to which the climate warms in the future will depend on natural climate variability and the level of greenhouse gas emissions. If greenhouse gas emissions continue then average global temperatures will rise. However, some regions such as the Arctic will warm faster than others.
Pollen:
By analyzing pollen from well-dated sediment cores, paleo climatologists can obtain records of changes in vegetation going back hundreds of thousands, and even millions of years. Not only can pollen records tell us about the past climate, but they can also tell us how we are impacting
our climate.
Tree rings:
Because trees are sensitive to local climate conditions, such as rain and temperature, they give scientists some information about that area’s local climate in the past. For example, tree rings usually grow wider in warm, wet years and they are thinner in years when it is cold and dry.
What is the greenhouse effect?
A natural function of the Earth’s atmosphere is to keep in some of the heat that is lost from the Earth. This is known as the
greenhouse effect
.
The atmosphere allows the heat from the Sun (short-wave radiation) to pass through to heat the Earth’s surface.
The Earth’s surface then gives off heat (long-wave radiation).
This heat is trapped by
greenhouse gases
(eg methane, carbon dioxide and nitrous oxide), which radiate the heat back towards Earth.
This process heats up the Earth.
What human factors increase global warming?
Burning fossil fuels, eg coal, gas and oil - these release carbon dioxide into the atmosphere.
Deforestation - trees absorb carbon dioxide during photosynthesis. If they are cut down, there will be higher amounts of carbon dioxide in the atmosphere.
Dumping waste in landfill - when the waste decomposes it produces methane.
Agriculture - agricultural practices lead to the release of nitrogen oxides into the atmosphere.
What are the natural factors increasing global warming?
There are also natural factors which contribute to increased global warming:
Orbital changes - the Earth has natural warming and cooling periods caused by
Milankovitch cycles
or variations in the tilt and/or orbit of the Earth around the Sun (Wobble, roll and stretch theory).
Volcanic activity - during a volcanic eruption carbon dioxide is released into the atmosphere.
Solar output - there can be fluctuations in the amount of radiation from the sun. If there is high amount emitted there will be an increase in Earth’s temperatures.
