2. Atmosphere and Weather Flashcards
What is an energy budget
The amount of energy entering a system
The amount of energy being transferred in a system
The amount of energy leaving the system
What are the 6 components of the daytime energy budget
Incoming solar radiation Reflected solar radiation Surface absorption Sensible heat transfer Long-wave radiation Latent heat of evaporation
Incoming solar radiation
aka insolation
affected by latitude, season and cloud cover
Energy coming from the sun
Only 23-40% of insolation reaches the surface of the Earth
shortwave radiation from the sun
Reflected solar radiation
aka Albedo
Light materiels are more reflective than dark materiels
Water only has an albedo of 4%
Surface absorption
energy that reaches the earth’s surface and heats it
Rock is a poor conductor of heat
if the surface can conduct heat to lower layers then it will remain cool
Sensible heat transfer
Movement of air into and out of a specific area
rise of warm air and replacement by cooler air
Long-wave radiation
The radiation of energy from the earth into the atmosphere.
during the day there is a net loss of energy from the surface
Latent heat transfer (evaporation)
The energy used to evaporate water, which means that less energy will be available for raising local energy and temperature
4 factors of the night time energy budget
Longwave earth radiation
latent heat transfer (condensation)
Sub-surface supply
Sensible heat transfer
Long wave radiation at night
Loss of energy during cloudless nights
Reduced loss of energy during cloudy nights
Longwave radiation in hot areas
often cloudless nights
maximised energy loss
large diurnal temperature differences
Latent heat transfer (condensation)
At night, water vapour close to the surface condenses to form water as the air has been cooled by the cold surface. when water condenses, latent heat is released
Sub-surface supply
Heat transferred to the soil and bedrock can be released back to the surface at night.
offsets night time cooling a bit
Sensible heat transfer at night
cold air moving into an area reduces temperatures where as warm air may supply energy and raise temperatures
Warm air
rises
Absolute humidity
the amount of water in the atmosphere
Relative humidity
Water vapour in the air as a percentage of the maximum amount that can be held
increases as temperature rises
saturated air
relative humidity of 100%
Mist
visibility is reduced to between 1000m-5000m
relative humidity is 93%
Fog
visibility is reduced to >1000m
requirements for mist and fog to form
condensation nuclei e.g dust
condensation of moist air cools below its dew point
occur near ground level
how does condensation take place
cooling of air
more water added to atmosphere
calm, high pressure conditions required to prevent the air from mixing with drier air
e.g: water evaporates from warm surface and condenses into the cold air above to form fog
Advection fog
when warm air flows over a cold surface. the warm air reaches 100% relative humidity
Radiation fog
When the ground loses heat at night by longwave radiation. occurs during high pressure conditions
Dew
condensation on a surface as the temperature has dropped to increase the relative humidity
Temperature inversions
reversal of the normal temperature behaviour of the troposphere. cold air on the bottom
greenhouse gases
trapping of longwave radiation
tropics have a
positive budget
the poles have a
negative budget
How is the budget balanced between the poles and tropics
horizontal transfer of energy from equator to the poles via wind and ocean currents
When are the solstices
Jan, jun.
shortest days
When are the equinoxes
march, sept
longest days
high pressure
good weather
low pressure
poor weather
ITCZ
intertropical convergence zone
where winds between the tropics converge. an area of low pressure
Latitudinal variations of the ITCZ
a result of the movement of the overhead sun. In June the ITCZ is further north, in Dec it is further south
Doldrums
Light winds at the ITCZ
2 factors that affect the temperature on a global scale
angle of the overhead sun, thickness of the upper atmosphere
temperature at the equator
high quality insolation, insolation received for a long time, less atmosphere to pass through
temperature at the poles
sun is low in the sky, poor quality of insolation, thick atmosphere, high albedo
Specific heat capacity
the amount of heat energy required to raise an amount of water by 1 C
why does water heat slower
it is clear which allows the suns rays to be distributed across a wider area
tides and currents also distribute heat
How does the sea influence temperature
Water releases heat much more slowly than the land. in winter, sea air is much warmer than land air so onshore winds bring heat to coastal lands. however in summer coastal areas remain coller than inland sites
what are areas with coastal influence called
maritime or oceanic
how are surface ocean currents created
the prevailing winds blowin steadily over the sea
what are the patterns of surface ocean currents
clockwise in the northern and anticlockwise in the south
gulf stream
transports heat northwards then eastwards towards the british isles
oceanic convection movement
in polar regions, cold salty water sinks into the depths and makes its way to the equator
what factors affect air movement
pressure and wind, pressure gradient
air motion
air motion is caused by the unequal heating of the earths surface
pressure gradient
air blows from high pressure to low pressure . the poles have a high pressure, equator has a low pressure
coriolis effect
deflection of objects caused by the easterly rotation of the earth
air flowing from high pressure to low pressure is deflected to the right in the north and to the left in the south
geostrophic balance
balance between pressure gradient force and coriolis force
friction decreases…
wind speed, coriolis force
warm air is transferred…
polewards and is replaced by cold air moving to the equator
low pressure
air rises
high pressure
air that sinks
low pressure produces
rain
high pressure produces
dry condition
Jet streams
strong regular winds which blow in the upper atmosphere
Rossby waves
meandering rivers of air formed by westerly wind
Hadley cell
air is warmed at the equator, rises and travels polewards. it sinks at the subtropical anticyclone.
polar cell
cold air creates high pressure. air flows back to the poles. The poles have a high pressure due to the cold.
ferrel cell
driven by the movements of the polar cell and hadley cell
What are 2 general points about the circulation model?
Warm air is transferred polewards
Cold air moves towards the equator
What types of wind are found at high altitudes
easterlys
What states does atmospheric moisture exist in
solid, liquid, gas
evaporation
the absorption of heat. heat loss passes into the water as latent heat of vaporisation
condensation
release of latent heat locked in water vapour
reverse sublimation
heat is released when vapour converts to ice
sublimation
heat is absorbed
freezing
heat is released and temperatures drop
melting
heat is absorbed at temperatures rise
What 3 factors affect evaporation
initial humidity of air- dry air means stronger evaporation
supply of heat- hotter the air the more evaporation
wind strength - in calm conditions air becomes saturated more rapidly
What factors affect condensation
radiation cooling of the air
cooling of the air when it flows over a cold surface
adibiatic (expansive) cooling of air when it rises
precipitation
all forms of deposition of moisture from the atmosphere
What are adiabatic processes
processes that relate to the rising and sinking of air
why might air rise
convection from heat
orographic barriers
turbulence
frontal systems
What is atmospheric instability
uplift and adiabatic cooling of warm, moist air
atmospheric stability
the immediate sinking of upwardly displaced air
environmental lapse rates
the actual temperature decline with height, avg 6C/km
dry adibatic lapse rate
the adiabatic cooling and warming in dry air
what is cloud formation dependent on
unstable atmospheric conditions causing the rising of air and subsequent condensation
what are clouds made of
millions of tiny water particles held in suspension
low clouds indicate…
poor weather
appearance of stratus clouds
dense, grey and low lying
appearance of cumulus clouds
flat bottomed and heaped
what clouds may be formed in unstable conditions
cumulus clouds via convection
what clouds may be formed in stable conditions
stratiform
Banner cloud formation
orographic uplift under stable air conditions
Types of precipitation
convectional rainfall
frontal rainfall
orographic rainfall
hail
convectional rainfall
when the land is hot it heats the air. the air expands and rises. as it rises cooling and condensation occur. continued rising will cause rai to fall. common in summer, near the ITCZ, temperate areas
frontal rainfall
when warm air meets cold air. the warm air is forced to rise over the denser air. the warm air condenses and forms rain
orographic rainfall
air rises over a barrier, cools and condenses.
hail
formed by raindrops being carried up and down in vertical air currents in large cumolonimbus clouds
Thunderstorms
rapid cloud formation and heavy precipitation in unstable air conditions. instability exists to great heights causing strong updrafts to develop
where are thunderstorms common?
tropical and warm areas when air can hold lots of moisture
Snow
frozen precipitation. only forms when temperatures are below freezing and water vapour is converted into a solid.
what are the conditions required to form snow
warm moist air rising over high mountains, cooling it down or when warm air comes into contact with a very cold front
frost
a deposit of fine ice crystals on the ground.
how is frost formed
occurs on cloud free nights when radiation cooling has cooled water vapour enough to sublimate onto the surface.
dew
deopistion of water droplets onto a surface
conditions that dew is formed in
clear, calm anticylonic conditions (stable) when there is rapid radiation cooling at night. the temperature reaches dew point.
dew point
The dew point is the temperature to which air must be cooled to become saturated with water vapor. When cooled further, the airborne water vapor will condense to form liquid water. When air cools to its dew point through contact with a surface that is colder than the air, water will condense on the surface.
temperature inversion
cold air is found at ground level and warm air is above it, a reverse in normal circumstances where air temperature decreases with altitude
What are greenhouse gases
Gases that allow short-wave insolation to pass through but trap outgoing long wave radiation. they raise the temperature of the lower atmospheres. essential for life
What is the enhanced greenhouse effect
Human activity affecting the amount of greenhouse gases in the atmosphere
What greenhouse gases are increasing rapidly?
CO2, methane, CFC’s
How do human activities affect greenhouse gases
cattle raising gives off methane, destruction of natural rainforests (carbon sinks), burning of fossil fuels, release of synthetic chemicals e.g CFC
evidence for climate change
ice cores carbon analysis oxygen analysis pollen analysis sea level changes tree rings glacier retreat
Ice core sampling
show the gases (C, O) trapped in air bubbles in ice. shows temperature change over time. CO2 levels have been shown to be stable for 10000 years, but have risen from the mid 19th century onwards.
Carbone analysis
analysis of air bubbles trapped in the ice cores. the air bubbles have atmospheric gases
Pollen analysis
pollen is preserved as sediment in peat bogs and lakes. the preserved pollen can show the ecology of the past
Sea level changes
sea level is affected by things like volume of water stored as ice. past sea levels are shown by raised beaches, which can be dated. they indicate the amount of water stored as ice
evidence for medium term climate change
historical records
proxy records (paintings, literature, grape harvest)
climactic periods (little ice age, medieval warm period)
slightly unreliable due to the influence of other factors
Tree rings
a new ring is formed every year as a tree grows. trees are sensitive to climate change. thick ring= good conditions
thin ring= bad conditions
retreating glaciers
changes can be tracked via photos.
deposition of rocks from the glacier
show the amount of glacier melt
evidence for short term climate change
weather reports that have been collected from the 19th century
what are natural causes of climate change not influenced by anthropogenic forces
variations of the Earth’s orbit around the sun
variations in tilt of the earths axis
variations in sunspot activity
amount of dust in the atmosphere
changes in ocean currents as a result of continental drift
why is climate change a complex problem
large scale
affected by both natural and anthropogenic causes
long term feedback mechanisms
what are the effects of increased global temperature change
rise in sea levels, causing flooding in low lying areas
displacement of 200 million people
increase in storm activity
reduced rainfall over US and Southern Europe
water shortages
reduced crop yields
What are the findings of the Stern Review
Climate change is fundamentally altering the planet
risks of inaction are high
time is running out
what causes heat islands
anthropogenic heat height and arrangement of buildings materiels used to build strucctures presence of water pollutants
what are urban heat islands
microclimates within the urban area. there are troughs and peaks. however, overall the temperature difference is significant compared to rural areas
how are winds in urban areas modified
lower speeds
greater variability
large scale convection
urban areas have lower wind speeds than outlying suburbs
what are the differences in wind speed for rural and urban areas
rural: wind speeds dont change with height as there is less friction at the surface
urban: lower wind speed from more buildings producing friction and altering its direction
Large scale convection in urban areas
the heat island effect produces convection over the urban area, leading to lower air pressure. consequently air is drawn in from surrounding rural areas, similar to how land or se breezes are created
what is anthropogenic heat
the heat released by human activity
e.g metabolic heat, central heating systems, AC, industrial activites
what is the albedo for grass
16-26%
albedo of deciduous forest
15-20%
albedo of asphalt
5-20%
albedo of concrete
10-35%
how do pollutants affect the urban heat island
pollutants can form a dome that absorbs heat andd prevents some from escaping
How might clouds and precipitation be changed by the urban heat island
more cloud cover because of
increased condensation nuclei
enhanced convectional uplift
reducing the urban microclimate
more greenspaces, increase in albedo
