Weather & Climate Flashcards
1
Q
What meteorological instruments do you need to know?
A
- Rain gauge
- Sunshine recorder
- Maximum and minimum thermometer
- Anemometer and wind vane
- Barometer
- Hygrometer
- Stevenson Screen
2
Q
What is a Wind Vane?
A
- A wind vane is used to measure wind direction.
- A wind vane has the points of the compass (i.e. NESW) fixed and sited so that they point in the correct directions.
- Above the is an arrow that can be moved by very light winds.
When the wind blows it moves the arrow and swings it around so that the arrow is pointing to the direction from which the wind is coming.
3
Q
What is an Anemometer?
A
- An anemometer is used to measure wind speed.
- An anemometer has 3 or 4 metal cups that are fixed to metal arms that rotate freely on a vertical shaft.
- When there is wind the cups rotate.
- The stronger the wind the faster the rotation.
- The number of rotations is recorded on a meter to give the speed in kmph.
- An anemometer should be placed well away from buildings or trees that may interfere with the free movement of air – buildings may channel air through narrow passages between two buildings or decrease the flow of air by blocking its path.
4
Q
What is a Rain Gauge?
A
- Amounts of precipitation e.g. rain, snow, sleet or hail are measured using a range gauge.
- This consists of a cylinder in which there is a collecting can containing a glass or plastic jar and a funnel that fits on the top of the container.
- The gauge is placed in an open space where so that only raindrops enter the funnel, rather than run off from buildings/vegetation etc.
- The gauge is sunk into the ground so that the top of the funnel is about 30 cm above ground level. This is to prevent water splashing on the ground and then entering the funnel.
- Rainfall collects in the jar and this is usually emptied every 24 hours.
- It is poured into a tapered glass and measured in millimetres.
- Rainfall recorded for a day, week, month or year can be shown on a weather map.
5
Q
What is a Barometer?
A
- Measures pressure is the amount of air pressing down on the earth’s surface.
- The unit of measurement for air pressure is millibars (mb)
- The mean average pressure at sea level is said to be 1013 mb, so pressures below these are usually said to be low and pressures above this high.
- Low air pressure is associated with unsettled conditions (as warm air is rising off the surface of the earth – which later cools and condenses forming clouds and potentially rain).
- High pressure is associated with settled/clear conditions as cool air is descending and warming up.
- You can have aneroid (mechanical with a box that expands and contracts due to pressure) or mercury (Mercury indicates pressure on a tube, rises to fill vacuum) barometer
6
Q
What is a Hygrometer/Wet and Dry Bulb Thermometer
A
- Measures humidity in %RH (percentage relative humidity)
- Humidity is a measurement of water vapour in the air
- The hygrometer contains two thermometers - a dry bulb and a wet bulb
- The dry bulb is a normal thermometer
- The wet bulb has a wet cloth around the bulb
- If the air is not saturated (100% RH), water will evaporate from the cloth into the air, cooling down the substance in the wet bulb so the thermometer reads a lower reading
- To find out the depression of the wet bulb - find the difference (Dry bulb - Wet bulb)
- Use a relative humidity chart to find the humidity percentage in relative humidity (%RH)
7
Q
What is a Maximum-Minimum Thermometer?
A
- Measures the Maximum and Minimum temperature in degrees celcius
- The thermometer is U-shaped, so when the temperature rises, mercury-alcohol mixture pushes a metal inde upwards. This index remains at the highest temperature poit
- During colder periods, the index on the other side is pushed as the mercury pushes the other way
- These indexes can be reset with a magnet
8
Q
What is a Campbell-Stokes Recorder?
A
- The number of hours and minutes of sunshine received at a place can be measured on a sunshine recorder.
- This is a glass sphere partially surrounded by a metal frame.
- A strip of special card, divided into hours and minutes is placed below the sphere.
- When the sun shines, the sphere focuses the sun’s rays on the card.
- As the sun moves, the rays burn a trace on the card. At the end of the day the card is removed and replaced.
- The length of the trace represents the amount of sunshine the area received.
9
Q
Why are Stevenson Screens white?
A
White is the best colour to reflect heat off of the box.
10
Q
Why are Stevenson Screens elevated on stilts?
A
Being on stilts stops heat entering the box by conduction from the ground, which could affect thermometer readings
11
Q
Why do Stevenson Screens have slats?
A
The slats on the side of the box allow the wind to flow through the box as this will give the correct air temperature.
12
Q
What are the characteristics of a Stevenson Screen?
A
- Shelters meteorological instruments (e.g. Hygrometer, Max-Min Thermometer, Barometer etc.) from ground heat, wind and precipitation to increase the acuracy of readings by them
- Wooden to insulate
- On stilts to avoid heat from the ground, should be elevated by 1.25m
- Slats to let wind go through
- Door facing north to recieve smallest amounts of light as possible
- Sited on flat ground, fenced away from intervention, away from artificial source of heat
13
Q
What are the advantages of digital weather instruments?
A
- More accuracy
- More precise readings
- Human error is minimised so they are more reliable
- No need to handle the instruments
- Data is continuous, no dates are ommited
- Data can be directly logged on to and graphed on a computer
- No need to read the instruments as it can be done remotely
14
Q
What are the main types of clouds?
A
- Stratus
- Cumulus
- Cumulonimbus
- Cirrus
15
Q
Describe the Stratus Cloud
A
Layered clouds that are low, grey and shapeless and usually are like a blanket of cloud over an area. They can bring some drizzle and rain.
16
Q
Describe the Cumulus
Cloud
A
Clouds that move quite quickly. They are white and fluffy and look like cotton wool. They can bring rain showers – especially when the base is grey.
17
Q
Describe the Cumulonimbus Cloud
A
Very deep clouds that climb high into the atmosphere. They often contain a lot of heavy rain and are associated with thunder and lightning storms.
18
Q
Describe the Cirrus Cloud
A
Very high clouds that are wispy and made up from ice crystals.
19
Q
What are the main natural reasons for the formation of hot deserts?
A
- 15 - 30 degrees from the equator Hadley cells
- Rain shadows by mountains
- Western coasts
- Regions far inland
20
Q
Explain why regions from 15 to 30 degrees from the equator have more deserts
A
- Air around the Tropics of Capricorn and Cancer is dry
- This is a zone of high air pressure where the air sinks.
- Air at the equator rises and cools - condensation then forms rain.
- The air then moves north and south due to the stratosphere until it gets to about 30° north and south of the equator, where it sinks.
- This air is dry, and no condensation can form, so there is no rain.
- This is known as the Hadley Cell. It shows how air moves around the atmosphere near the equator and tropics.
21
Q
Explain why rain shadows result in deserts
A
- Some deserts form in the rain shadow of mountains
- Air is forced to rise over mountains, air cools and condensation occurs, causing rain to fall over the mountains
- The dry air sinks down the other side of the mountain
22
Q
Explain why deserts occur on some western coasts
A
- Some deserts are found on the western edges of continents
- They are caused by cold ocean currents, which run along the coast
- They cool the air and make it harder for the air to hold moisture
- Some moisture falls as rain before it reaches the land
- As the air is warmed, the air is able to hold more mositure, which results little condensation and less rainfall
23
Q
Exlain why deserts occur inland sometimes
A
- Some deserts form in areas that lie at great distances from the sea
- The air here is much drier than on the coast as there are no sources of moisture
- This is because the air loses moisture as it moves inland due to a prevailing wind, so it is dry before it arrives at the desert
24
Q
Explain why deserts on western coast experience fog
A
- They are caused by cold ocean currents, which run along the coast
- The cold air is blown over the land at a low altitude, below the warm air, leading to condensation at a low level, producing fog.
25
Q
What are typical plant adaptations in deserts?
A
- Small leaves - These ensure that less water is lost from the plant by transpiration because the leaf has a smaller surface area.
- Tap roots - These are long roots (7-10 metres long) that reach deep under the ground to access water supplies. The tap roots are much longer and bigger than the plant which is visible at the surface.
- Spines - Some plants have spines instead of leaves, eg cactuses. Spines lose less water than leaves so are very efficient in a hot climate. Spines also prevent animals from eating the plant.
- Waxy skin - Some leaves have a thick, waxy skin on their surface. This reduces water loss by transpiration.
- Water storage - Some plants, known as succulents, store water in their stems, leaves, roots or even fruits. Plants which store water in their leaves and stems also have a thick waxy skin so that they lose less water by transpiration.
26
Q
What are the typical animal adaptation in deserts?
A
- Nocturnal desert animals keep cool by being active at night
- Other desert animals get away from the sun’s heat by digging underground burrows
- Some animals have big ears with many blood vessels to lose heat and help keep them cool
- Some animals have light-coloured coats to reflect rather than absorb sunlight and to protect them from intense heat
- Some creatures get the moisture they need from their food, e.g. succulents, so they don’t need to drink much water
- Kidneys concentrate urine to reduce water loss
- Large feet to stop sinking into the sand
- Evolved to survive for long periods without water or food
27
Q
Def. Desert
A
A an area that recieves less than 250 mm of rain per year
28
Q
Describe the location of the Sonoran Desert
A
- It spreads throughout the USA and Mexico.
- It is located in a subtropical region of North America
- Located between 25 - 33 degrees from the equator
29
Q
Describe the characteristics of the Sonoran Desert climate
A
- The Sonoran is the hottest desert in both the USA and Mexico, and rarely freezes
- Summer air temperatures regularly exceed 40°C, and often reach 48°C.
- High diurnal temperature range - diurnal swings of 15°C or more are common. This is because there is low humidity and little cloud cover, which allows for rapid heating during the day and rapid cooling at night.
- A very dry climate for most of Arizona and New Mexico.
- Annual precipitation in the Sonoran Desert ranges from 75-500 mm depending on location.
- The Sonoran desert has a bi-seasonal rainfall pattern.
- From December to March frontal storms from North Pacific Ocean occasionally bring widespread, gentle rain to the northwestern areas.
- From July to mid-September, the summer monsoon brings surges of wet tropical air and frequent but localized violent thunderstorms.
