Weather and Climate questions and answers

Here are the past questions (other than comment on) for the weather and climate part of the course... Again the questions are in purple with the command word in blue, the answers are then in green with the mark scheme in black.
Remember to read how you will get the marks because that is what you need to write in your exam :D Have fun!!!!!!!!

Explain how urban structures and layout affect winds. (8 marks)

The surface area of cities is uneven due to the varying height of the buildings. Buildings in general exert a powerful frictional drag on air moving over and around them. This creates turbulence, giving rapid and abrupt changes in both wind direction and speed. Average wind speeds are lower in cities than in the surrounding areas and they are also lower in city centres than in suburbs. High rise buildings may slow down air movement but they also channel air into the canyons between them.

Winds are therefore affected by the size and shape of buildings. For a single building, air is displaced upwards and around the sides of the building and is also pushed downwards in the lee of the structure. On the windward side, the air will push against the wall on this side with relatively high pressures. As the air flows around the sides of the building it becomes separated from the walls and roof and sets up suction in these areas. On the windward side the overpressure, which increases with height, causes a descending flow which forms a vortex when it reaches the ground and sweeps around the windward corners.

This vortex is considerably increased if there is a small building to windward. In the lee of the building there is a zone of lower pressure, causing vortices behind it.

If two separate buildings allow airflow between them, then the movement may be subject to the Venturieffect in which the pressure within the gap causes the wind to pick up speed and reach high velocities.

Usually buildings are part of a group and the disturbance to the airflow depends upon the height of the buildings and the spacing between them. If they are widely spaced, each building acts as an isolated block, but if they are closer, the wake of each building interferes with the airflow around the next structure and this produces a very complex pattern of airflow.

Usually buildings are part of a group and the disturbance to the airflow depends upon the height of the buildings and the spacing between them. If they are widely spaced, each building acts as an isolated block, but if they are closer, the wake of each building interferes with the airflow around the next structure and this produces a very complex pattern of airflow.

 

Mark scheme
Level 1 (1-4 marks) (mid point 3)
Simple statements of how buildings influence air flows such as acting as windbreaks, creating turbulence and causing a .canyon. effect.

Level 2 (5-8 marks) (mid point 6)

Detailed relationships between buildings and air flow, such as the importance of the separation of buildings, and the complexity of flow around a building/buildings.

With reference to examples, discuss how pollution reduction policies have attempted to lessen the incidence of particulate pollution and photochemical smog. (10 marks)

Notes for answers
There are a number of ways in which governments and other organisations have tried to reduce atmospheric pollution in cities.

Clean Air Acts: After the London pea-souper of 1952, the government decided legislation was needed to prevent so much smoke entering the atmosphere. The act of 1956 introduced smoke-free zones into the UK.s urban areas and this policy slowly began to clean up the air. The 1956 act was reinforced by later legislation. In the 1990s, for example, very tough regulations were imposed on levels of airborne pollution, particularly on the level of PM10s in the atmosphere. Local councils in the UK are now required to monitor pollution in their areas and establish Air Quality Management Areas where levels are likely to be exceeded. Some have planted more vegetation to capture particulates on leaves.

Vehicle control in inner urban areas: a number of cities have looked at ways of controlling pollution by trying to reduce the number of vehicles that come into central urban areas. In Athens, for example, the city declared an area of about 2.5 km² in the centre traffic free. Many British towns and cities have pedestrianised their CBDs. In London, attempts to control vehicle numbers have included introducing a congestion charge which means vehicle owners have to pay if they wish to drive into the centre. The Greater London Low Emission Zone is an extension of this. In Mexico City, the city council passed driving restriction legislation known as the Hoy no Circula (don.t drive today). This bans all vehicles from being driven in the city on one weekday per week, the vehicle.s registration number determining the day.

More public transport: attempts have been made to persuade people to use public transport instead of cars. Such schemes have included Manchester.s development of a tram system (Metrolink), the development of bus-only lanes into city centres, the growth of park-and ride schemes in many British cities and the encouragement of carsharing schemes.

Zoning of industry: industry has been placed downwind in cities if at all possible and planning legislation has forced companies to build higher factory chimneys to emit pollutants above the inversion layer.

Vehicle emissions legislation: motor vehicle manufacturers have been made to develop more efficient fuel-burning engines and to introduce catalytic converters which remove some of the polluting gases from exhaust fumes. The switch to lead-free petrol has also reduced pollution.

 

Mark scheme

Level 1 (1-4 marks) (mid point 3)

Simple statements of pollution reduction policies which could apply to any area of the world, and to any form of atmospheric pollution. No specific detail provided.

Level 2 (5-8 marks) (mid point 6)

Specific statements of pollution reduction policies which can be clearly attributed to named areas and/or forms of pollution access this level.

Level 3 (9-10 marks) (mid point 9)

A fully developed answer, with good elaboration and discussion of a variety of pollution reduction policies each clearly attributed and being different from each other.

With the aid of a diagram, describe the structure of the atmosphere. (8 marks)

Notes for answers

• The troposphere: temperatures generally decrease with height (averaging 6.5ºC per km). The top of this layer is marked by a boundary called the tropopause where temperatures remain fairly constant, this occurs at a height of about 8km at the poles and 17km in the tropics and it can vary with seasonal changes in climate. The tropopause acts as a temperature inversion forming an effective ceiling to any convection in the troposphere and so provides an upper limit to the earth.s weather systems.

• The stratosphere: extends to about 50km above the Earth.s surface and within this layer temperatures increase with height. Also within this layer, ozone absorbs and filters out ultraviolet radiation. The upper limit of the stratosphere is marked by the stratopause.

• The mesosphere: temperatures again decrease with altitude to the mesopause.

• The thermosphere: temperatures start to rise again at a constant rate up to as much as 1500ºC.

Level 1 (1-4 marks) (Midpoint 3)

Simple statements/annotations of the structure of the atmosphere. Naming of terms with no development; or one zone described well (likely to be the troposphere). A basic diagram.

Level 2 (5-8 marks) (Midpoint 6)

Detailed description of at least two zones within the atmosphere with some development of each. Recognition and description of three zones should achieve maximum credit. Accurate/detailed diagram.

No diagram = maximum 6 marks.

Explain how each of altitude and oceanic circulation influence climate. (10 marks)

Notes for answers

Altitude: exerts a significant effect on temperature in mountainous areas as temperatures decrease steadily with height above sea level. Hence, areas such as the Himalayas, Alps, Rockies and Andes are cooler than similar latitudes. Air which is moving through the atmosphere cools on rising, or warms up on descending, according to adiabatic laws. In the atmosphere the change of temperature with height is called the environmental lapse rate (ELR). The average value for ELR is 6.5ºC for every 1000 metres. However, this value varies both with height and with time, being higher in the summer season.

Candidates may also refer to the influence of mountains on the pattern of upper winds. Rossby waves are thought to be due to the upper air flow being forced to divert around the great north-south mountain ranges of the Rockies and Andes in the northern and southern hemispheres respectively. Also allow rainshadow effect. Allow relief rainfall and anabatic/katabatic winds.

Oceanic circulation: the large-scale movement of water within the oceans is part of the horizontal transfer of heat from the tropics to the polar regions and is responsible for around 20% of the total transfer of heat within the energy budget. Each ocean has its own particular circular pattern of currents (called a gyre) that are produced as masses of water move from one climatic zone to another. Ocean currents are largely set in motion by the prevailing surface winds. They allow heat to become more equably distributed throughout the world.s major climate zones. The world.s major ocean currents are particularly dominant along the western sides of the ocean basins and currents that are less

well-defined and relatively weak are on the eastern sides. Heat is transferred by warm ocean currents, such as the North Atlantic Drift in the Atlantic Ocean, from the low to high latitudes. This warming influence is particularly dominant between latitudes 40º to 65º where winds blow onshore, on the western sides of continents and is confined to the winter season. Cold ocean currents generally have less effect upon temperatures because they usually lie under off-shore winds.

One exception is the Labrador Current off the East coast of North America.

Allow reference to regional scale . e.g. effects of North Atlantic Drift, El Nino/La Nina.

Mark scheme

Level 1 (1-4 marks)(Midpoint 3)

Simple statements of influence of altitude and oceanic circulation on climate. No specific detail or elaboration is provided; or discussion of one aspect only.

Level 2 (5-8 marks) (Midpoint 6)

Both elements covered with specific or detailed statements of influence of altitude or oceanic circulation on climate; may be still an imbalance of influence.

Level 3 (9-10 marks) (Midpoint 9)

A fully developed answer, with good elaboration and  explanation of a range of influences, with both elements reaching a Level 2 response.

The answer demonstrates both breadth and depth of understanding