Weather And Climate Flashcards
1
Q
What is climate?
A
Average weather over an area over 30 years
2
Q
What is the atmosphere?
A
A mixture of gases held to the earth by gravitational force.
3
Q
What gases make up the atmosphere?
A
78% nitrogen
21% oxygen
1% mixture including carbon dioxide and methane
4
Q
How many layers is the atmosphere made up of?
A
4
5
Q
What are the four layers of the atmosphere?
A
Troposphere
Stratosphere
Mesosphere
Thermosphere
6
Q
What are the key features of the troposphere?
A
From Earth’s surface to 12km
Temperature decreases with altitude at 6.5 degrees c per km
No weather past tropopause
Jet streams are found just below the tropopause
7
Q
Why does temperature decrease with altitude in the troposphere?
A
The Earth’s surface warms the troposphere and so the further away the cooler it gets.
8
Q
What are the features of the stratosphere?
A
12km to 50km up
Temperature increases with altitude because the ozone layer is found here which absorbs uv radiation
Warming is greater over polar regions than tropical regions
Global warming has been linked to the stratosphere
9
Q
What are the features of the mesosphere?
A
50km to 85 km
Temperature decreases with altitude as is warmed by the stratosphere and lacks components to trap solar energy
10
Q
What are the features of the thermosphere?
A
85km to 1000km
Temperature increases with altitude because small amounts of oxygen absorb uv radiation and is also close to the sun
Temperatures can reach 1500 degrees c
11
Q
What is the atmospheric heat budget?
A
Heat gained and lost by the earth
12
Q
What is insolation?
A
Energy from the sun in the form of short wave radiation
13
Q
How is incoming insolation divided up according the the atmospheric heat budget?
A
50% absorbed by the surface of the earth, released as long wave radiation and heats the troposphere
25% reflected back into space by the air and clouds
20% absorbed by air and clouds in the atmosphere
5% reflected back into space by the Earth’s surface
14
Q
What is albedo?
A
The reflectivity of a surface
It is measured as a ratio of incoming:reflected radiation
The average albedo value for the earth is about 30%
15
Q
Is the balance of radiation loss to gain equal for the planet?
A
Yes
16
Q
Is the balance of radiation loss to gain equal for all latitudes?
A
No
17
Q
Do low latitudes have a positive or negative heat balance?
A
Positive
18
Q
Do high latitudes have a positive or negative heat balance?
A
Negative
19
Q
Why do different latitudes have variations in radiation loss and gain? 3 reasons
A
Length of day and night
Angle of obliquity
Variations in albedo
20
Q
How is the imbalance of radiation for latitudes rectified?
A
By heat transfers
21
Q
What would be different about the earth if heat transfers didn’t occur?
A
The poles would be 25 degrees c colder and the tropics 14 degrees c hotter
22
Q
What horizontal transfers rectify radiation imbalance?
A
80% transferred from tropics by winds- jet streams, depressions, hurricanes 20 % by the movement of warmer ocean currents polewards
23
Q
What vertical transfers are there?
A
Convection conduction radiation and latent heat
24
Q
Why are higher altitudes colder?
A
The Earth’s surface heats the atmosphere through conduction and air pressure decreases soo there are fewer air molecules and they move more slowly
25
What four main factors decide how much solar radiation the atmosphere receives?
Solar constant (how active the sun is)
Distance from the sun
Height of the sun in the sky
Length of day and night
26
How do winds redistribute energy from the equator to the poles?
Differences in air pressure are caused by differences in atmospheric heating between the equator and the poles
Winds are part of global atmospheric circulation cells
These cells have bodies of warm rising air and of cool falling air
27
What are winds?
Large scale movements of air caused by differences in air pressure
28
What are the three main types of cell in the tricellular model?
Hadley
Ferrel
Polar
29
What is weather?
Day to day state of the atmosphere, short term atmospheric conditions
30
From the North to the South of the Earth what are the winds that are acting on the Earth?
Polar Easterlies, South Westerlies, North Easterly Trade Winds, South Easterly Trade Winds, North Westerlies, Polar Easterlies
31
What happens at the equator according to the tricellular model?
The sun warms the earth, transferring heat to the air above, causing it to rise (Hadley cells). Rising air causes low pressure, clouds and rain. This is called the Inter Tropical Convergence Zone (ITCZ) As the air rises it cools and moves out to 30 degrees North and South of the equator.
32
What happens 30 degrees North and South of the equator according to the tricellular model?
As the air rises it cools from the equator and moves out to 30 degrees North and South of the equator. The cool sinking air creates high pressure. This is the area where sub tropical jet streams are found here where the air the Hadley cell and the Ferrel cell sinks. The cool air reaches the ground surface and move as surface winds either back to the equator or towards the poles (Ferrel cells). Surface winds going towards the equator are called trade winds which are heated by solar radiation causing them to rise, condense and form clouds. Surface winds going towards the poles are called westerlies.
33
What happens 60 degrees N and S of the equator according to the tricellular model?
The warmer surface winds meet colder air from the poles. The warmer air is less dense so rises and creates low pressure. Some of the air joins the ferrel cell and moves back towards the equator and the rest joins the polar cells and moves towards the poles. At the poles the cool air sinks, creating high pressure and is drawn back towards the equator in surface winds.
34
How can the ITCZ characteristics vary?
In location or width
35
What consequences can variations in the ITCZ have on surrounding climates?
Can lead to droughts such as the Sahel droughts of the early 1970s and most of the 1980s.
36
How is energy redistributed from the equator to the poles?
By ocean currents
37
What are ocean currents?
Large scale movements of water caused by differences in water density. They transfer heat from warmer to cooler regions. They form giant loops that travel clockwise in the N hemisphere and anticlockwise in the S hemisphere.
38
What does water density depend on?
Water temperature and salinity
39
What are currents affected by?
Surface winds, position of land masses and other currents
40
What do ocean current affect?
The climate of regions- The Golf Stream keeps Western Europe much warmer than it would be otherwise.
41
What are the 5 major climate controls?
Latitude, altitude, proportion of land and sea, prevailing winds and air masses, surface ocean currents.
42
How does latitude control climate?
Influences length of daylight hours and the angle of incidence
43
How does altitude control climate?
Insolation heats the surface of the land which warms the air above it by conduction and convection. Further away from surface, less long wave radiations, so cooler it is. Also, at altitude the air is less dense and so is less able to absorb long wave radiation.
44
What is the average environmental lapse rate?
6.4 degrees C per 1000m
45
How does proportion of land and sea control climate?
Land has a higher rate of thermal conductivity than the sea. Land heats and cools down more quickly. Places nearer the sea (maritime areas) have a more moderate climate than those at distance from it (continental areas.)
46
How do prevailing winds and air masses control climate?
Wind brings air from other locations that has acquired the temperature and water content of its source area. Winds bringing air masses from the sea will be moisture laden. Winds from high latitudes will be cold.
47
How do surface ocean currents control climate?
Warm ocean currents raise temperatures in places bordering the sea and vice versa. The coriolis force acts to deflect the ocean flows which creates a circular motion (gyre) that travels clockwise in the N hemisphere and anticlockwise in the S hemisphere.
48
What is dry adiabatic lapse rate?
10degrees C every 1000m when dry air is forced over a mountain, the consequential fall in volume means temperatures will fall more.
49
What is saturated adiabatic lapse rate?
Saturated air leads to the release of latent heat and so reduces falling temperature
50
How does cloud cover affect variations in global insolation?
The highest insolation values lie close to the tropics and not to the equator. This is because these subtropical regions are largely free from cloud whereas at the equator there's much more cloud cover.
51
How does the proportion of land and sea affect patterns of global insolation?
Evaporation from the oceans tend to cause much more cloud cover which reduce insolation reaching the Earth's surface. Land areas also tend to be darker and so absorb more radiation.
52
What is El Nino?
After the seasons El Nino (and La Nina) are the single largest cause of year to year climate variability on the Earth. El Nino brings unusually warm water between the coasts of Ecuador and Peru. El Nino refers to the warmer eastern tropical pacific seas is forced westwards which results in drenching rains over south America/ East Pacific. Meanwhile, Indonesia/ West Pacific experiences drought.
53
What is La Nina?
La Nino refers to unusually cold sea surface temperatures found in the eastern Pacific. La Nina brings excess rain in the West Pacific and dry conditions in the east Pacific.
54
What is the average return period of El Nino and La Nina events?
4 years and in equal numbers
55
Describe UK climate
UK climate is temperate. Temperature varies with the seasons from 5 degrees C in Jan and 20 in August. Rainfall is fairly constant, with 120mm in Jan and 65mm in May. Winds are mostly warm south westerlies, cold northern winds are also common, winds are generally stronger in Autumn.
56
What four factors affect the UK climate?
Latitude, Location in relation to atmospheric cells, Maritime location, Located near the Gulf Stream.
57
How does latitude affect UK climate?
It is between 50 and 55 degrees N, it doesn't get very hot because the sun is never very high in the sky and it doesn't get very cold because there are several hours of daylight.
58
How does location in relation to atmospheric cells affect UK climate?
The UK is on the northern edge of a Ferrel cell. Surface winds bring warm air from the south which rises and creates low pressure systems which bring rain all year round.
59
How does maritime location affect UK climate?
As it's surrounded by water, which gains and loses heat more slowly than land does, there are cool winds blowing to the land in the summer and vice versa in the winter. Meaning that summer is cooler and winter warmer than inland locations of the same latitude.
60
How does the Gulf Stream affect UK climate?
Makes the UK warmer as it lies within the cool temperate western maritime climate belt so doesn't experience temperature extremes.
61
How does temperature vary within the UK?
Warmer in the south because there's more insolation as the sun is higher in the sky and there's more daylight hours, annual average max temps 13.6 in Cornwall and 9.3 in the north of Scotland.
62
What are the January averages for the UK temperature?
Scottish highlands and Snowdonia colder because of altitude. Prevailing winds from Caribbean warm the south west. Warmer temperatures around the coast because it takes the sea a long time to warm up and cool. Urban heat island effect is present around London.
63
What are the July averages for the UK temperature?
Greater temperature extremes. Urban heat island more extreme in Summer- can see around London, Midlands and North West conurbation. Warming influence around the coast is less extreme because the sea hasn't had time to warm up.
64
How does precipitation vary within the UK?
Wetter in the west than the east- particularly when comparing Scotland to London because south westerly surface winds bring warm wet air from the Atlantic Ocean. The air reaches the west side of the UK and is forced up over the land. The air cools, condenses and it rains- relief rainfall. The east in in the rain shadow.
65
How do winds vary within the UK?
Winds are stronger in the west because south westerly surface winds come over the ocean and there's nothing to slow the winds down. When the winds hit land, they become weaker. Winds are stronger at higher altitudes because there are fewer obstacles to slow them down.
66
What is an air mass?
A large body of air that has similar temperature and humidity levels that cover large area and can travel long distances.
67
What are the 5 main air masses that affect the UK?
```
Arctic
Polar maritime
Polar continental
Tropical maritime
Tropical continental
```
68
Describe arctic air masses
Come from the north, forms over the arctic ocean at high latitudes and bring very cold, wet air.
69
Describe polar maritime air masses
Form at high latitudes over the North Atlantic ocean and bring cold, wet air.
70
Describe polar continental air masses
Form at high latitudes over Siberia. They bring cold, dry air.
71
Describe tropical maritime air masses
Form at low latitudes over the Atlantic ocean and bring warm wet air.
72
Describe tropical continental air masses
Form at low latitudes over Africa and bring warm, dry air.
73
What conditions do arctic air masses bring?
Very cold conditions in winter and cold in spring; winds often strong in the north, brings heavy snow to Scotland and N England.
74
What conditions do tropical maritime air masses bring?
Warm summer conditions, often tempered by moderate winds, especially in western coastal areas. Warms as it crosses the Atlantic to become unstable which can bring heavy cloud and frequent rain showers. Depressions are associated with tropical maritime air masses. Gives mild temperatures in winter often with thick stratus cloud and hill/coastal fog.
75
What conditions do tropical continental air masses bring?
May bring heatwave conditions, with temperatures in high 30s, very stable air at low levels gives cloudless, extremely dry conditions, may last several days especially if there's a blocking anticyclone. Upper levels may become unstable due to convectional uplift leading to intense, localised thunderstorms.
76
What conditions do polar maritime air masses bring?
Strong winds, heavy showers as it crosses highland regions, possibly falling as snow in winter, slowly warms as it moves south, it picks up moisture from the sea and becomes unstable, very common, especially in winter and gives cool conditions all year round.
77
What conditions do polar continental air masses bring?
Begins stable but warms slightly over the north sea where it picks up moisture to become unstable and brings heavy snow to eastern Britain. Gives very cold conditions in winter with daytime temperatures at or below freezing and at night time as low as -10 degrees C. Wind chill factor very high.
78
Define a depression
Low pressure weather systems. They usually form when the tropical maritime and polar maritime air masses meet over the Atlantic. Often below 1000mb.
79
How does a depression form?
1. Warm air constantly moves out of tropical areas, towards the poles. A warm front is the leading edge of a warm air mass.
2. Cold air moves out of polar areas towards the tropics. A cold front is the leading edge of a cold air mass.
3. Where the air masses meet, the warm air rises above the cold air because warm air is less dense.
4. The rising warm air means that atmospheric pressure is reduced.
5. Strong winds blow from surrounding areas of high pressure towards the area of low pressure and the whole system rotates as air continues to rise.
6. Cold fronts move more quickly than warm fronts so the cold front catches up with the warm front.
7. When this happens the warm air behind the warm front is undercut by the incoming cold front and is lifted away from the ground. It now sits above the cold air forming an occluded front. The warm air rises into the upper atmosphere and the depression dissolves.
80
What are the characteristics of a depression?
Winds often strong, blow inwards in an anticlockwise direction.
Generally last 2-3 days.
Ahead of the warm front, it's cool because cool air is overhead. Thin clouds form.
As the warm front passes, conditions on the ground get warmer and low thick clouds form.
When the warm air is overhead, it's warm and there's no cloud.
As the cold front passes, cool air brings the temperature down. Rapidly rising air leads to condensation and heavy showers.
When the cold front catches the warm front, there's less rain and cloud cover decreases,, wind speed also decreases. The depression dies out.
81
What is an anticyclone?
Areas of high pressure represented on a weather map with closed isobars where pressure increases towards the centre. They move slowly and can remain over an area for several days or weeks. Air is subsiding, warming as it falls, producing a decrease in relative humidity and so a lack of cloud development and dry conditions. Winds tend to be weak and flow gently outwards in a clockwise condition.
82
What are the winter weather conditions associated with anticyclones?
Cold daytime temps from below freezing to a max of 5 degrees c
Very cold nightime temps, below freezing with frosts because clear skies allow loss of heat through radiation
Low level cloud and radiation fogs
High levels of atmospheric pollution in urban areas, trapped by a temperature inversion.
83
What are the summer weather conditions associated with anticyclones?
Hot daytime temps can be 25 degrees c plus.
Warm nighttime temps not falling below 15 degrees c
Absence of clouds leads to intense insolation.
Rapid radiation at night can lead to great temp inversions, dew and morning mists
Lack of rain
Thunderstorms may occur
Coastal areas may get fogs.
84
What conditions are fogs usually associated with?
Anticyclonic
85
What is fog?
Cloud at ground level that restricts visibility to less than 1km. It consists of tiny water droplets suspended in the atmosphere.
86
What are the two types of fog?
Advection and radiation
87
How is radiation fog formed?
Under clear night skies when a moist atmosphere cools through radiation of heat from the ground surface. This cooling extends a great distance above the ground and is encouraged by light winds. The air is cooled to its due point and condensation occurs. It is common in winter, when long hours of darkness allow max cooling. It disperses through an increase in wind speed or through warming of the air and evaporation.
88
How is advection fog formed?
Fog that forms when a mass of air moves horizontally across a cooler surface. Air is cooled to its dew point and condensation occurs. This type of fog is common at coasts and over the sea in summer.
