Global and synoptic scale processes - Climatology Flashcards
Weather vs climate
Weather = state of atmosphere at any given time, short-term variability
Climate = long term state of the atmosphere, seasonal variability/long term trends
Processes responsible for vertical motion operate on:
Processes responsible for horizontal motion operate on:
Processes of similar importance operate on:
- Microscale
- Macroscale
- Mesoscale
Atmosphere requires what to operate maintain the processes that operate at spatial and temporal scales
Energy
Energy cannot be
Created nor destroyed (first law of thermodynamics)
How does the Earth recieve energy from the sun (starting point)
By injecting radiative waves of electromagnetic energy into space and therefore into earth
Primary energy source from the sun
Radiation
What would result in the absense of continuous radiation from the sun
Atmospheric motion would cease within days due to friction
What carries energy between sun and earth
Light through a vacuum by means of electromagnetic radiation
How does electromagnetic radiation travel from the sun
In wave-like patterns/oscillations
Wavelengths vary and are ________ to frequency
Inversely proportional
Speed of light equation
Frequency x wavelength = speed of light
f x λ = c
Speed of light =
3 x 10^8 m/s
Absolute zero =
-273.15 degrees or 0 K
What objects emit electromagnetic radiation
Anything above absolute zero
Suns exterior temperature =
6000 k
Blackbody
An object that absorbs radiation that strikes from it and emits radiation at a max rate for its given temperature e.g the sun
The amount of energy emitted by an object is a function of its
Temperature
Equation that describes the thermal intensity of radiation from an object
Stefan-Boltzmann law
Stefan-Boltzmann law
Energy = emmissivity of the object x Stefan Boltzmann constant (5.67x10^-8) x temperature^4
Equation used to calculate maximum wavelength
Wiens law
Wiens law
λmax = 2897/temperature
Suns dominant wavelength
0.48 um
Primary constituents in the atmosphere
Nitrogen (78%) Oxygen (21%)
Which segment of the atmosphere has over 80% of the air
Troposphere
Solar constant
The total amount of energy of all wavelengths received at the top of the earth’s atmosphere perpendicular to the solar beam
Tropics recieve _____ times more
2.5
Is energy more concentrated on a perpendicular or surface at a lower angle
Perpendicular surface
Varaition in daily insolation at the top of the atmosphere is controlled by
Earths revolution and rotation
Earths speed of orbit averages
107,280 km hr
The plane in which earth moves around the sun
Ecliptic plane
The closest and furthest point of earth to the sun are the
Perihelion and aphelion
The tilt of earths axis from the plane of ecliptic
23.5 degrees
Primary reason for the seasons
Orientation of the polar axis in relation to its orbit around the sun
How does sunlight characteristics change between seasons
Zenith angle at noon changes between seasons, as well as the location of sunrise and sunset
Radiation as it passes through the atmosphere can be
Absorbed, reflected, transmitted
Absorption, reflection and transmission of radiation is dependent on
Wavelength
What happens to short wave radiation
- Reflected at the top of the atmosphere 2. Reflected or absorbed by gases in the atmosphere 3. Transmitted to the surface and then either absorbed or reflected back upward into the atmosphere (Albedo)
Why is the sky blue
Because when incoming radiation reaches earths atmosphere, some of it is scattered by atmospheric gases in all directions. Atmospheric gases scatter short waves most effectively which are blue.
Reflection at the earths surface is called
Albedo
Albedo values:
Snow -
Light roof -
Water bodies -
Brick and stone -
Grass -
Concrete/dry -
Crops -
Forests -
Asphalt/black top -
Dark roof -
Moon -
Earths average albedo -
Snow - 80-95%
Light roof - 35-50%
Water bodies - 10-60%
Brick and stone - 20-40%
Grass - 25-30%
Concrete/dry - 17-27%
Crops - 10-25%
Forests - 10-20%
Asphalt/black top - 5-10%
Dark roof - 8-18%
Moon - 6-8%
Earths average Albedo - 31%
What happens to long-wave radiation
The earths surface emits LW radiation at temperatures high relative to the top of the atmosphere and radiation that escapes past atmospheric gases cools the planet, Atmospheric gases emit LW radiation in all directions with the downward emissions warming the surface (greenhouse effect) and the upward emissions joining that escaped earth LW radiation.
How does water in the atmosphere affect its buoyancy
More moisture equals more bouyant
The only substance that occurs in its three states naturally on earths surface and has the highest heat capacity of all common solids and liquids (meaning it requires significant energy to change temperature)
Water
Waters highest and lowest densities
Liquid (4 degrees) and solid
Heat exchange associated with the change in phase of water
Latent heat
Heat of vaporization
The amount of energy required to convert a saturated liquid into a vapour
The motion of air is caused by
Energy exchanges in the atmosphere which absorbs and releases tremendous amounts of heat.
Clasius-Clapeyron relationship
Saturation vapour pressure of water increases with temperature, thus warmer air can hold more water
How does vertical motion relate to stable/unstable air
Vertical motion is suppressed in stable air and vertical motion is enhanced in unstable air.
Why does air density and pressure decrease with height
Because the atmosphere is compressible
How is air density calculated
With pressure and temperature measurements
Parcel
A body of air that has specific temperature and humidity characteristics
Ideal gas law
Pressure, density and temperature of a gas are dependent on each other
Does warm air produce lower or higher density of air
Lower
Rising air parcel cools by -
Falling air parcel warms by -
- Expansion
- Compression
What are adiabatic processes
Describes the warming or cooling rates for a parcel of expanding or compressing air
Adiabatic temperature change
Temperature change where there is no heat flow in or our of the system and is solely due to changes in pressure.
Atmospheric temperature profiles
Warmer with height -
Cooler with height -
No change with height -
- Inversion
- Lapse
- Isothermal
Stability states in the atmosphere
Unstable,
Conditionally unstable,
Stable,
Neutral state where no vertical motion occurs,
Three main cloud terms to describe shape and texture
Cumulus, stratus and cirrus
Both oceanic and atmospheric circulations operate to do what
Transport thermal energy from source to sinks
Factors controlling the motion of air
Pressure gradient force,
Coriolis force,
Friction
Pressure gradient force
Initial stimulant for horizontal air motion
Pressure gradient force equation
Pressure gradient = ∆pressure/∆change
What does earths rotation produce
Coriolis force
Coriolis force
An apparent force used to explain deflection created by the earths rotation, which operates to the left of motion in the southern hemisphere, and is a function of wind speed and latitude
Coriolis force equation
Coriolis force = 2 x angular velocity of spin (7.29 x 10^-5) x wind speed x sin latitude
Why is the Coriolis force called an ‘apparent’ force
Because it results in deflection relative only to the earth’s surface
How does the deflection in the Coriolis effect operate
- Maximum deflection at the poles, no reflection at the equator 2. Deflection gets larger as wind speed increases
The geostrophic wind
Approximates the observed wind and is a result of the balance between the pressure gradient force and the Coriolis force
Impacts of friction on wind
Friction near the surface reduces wind speed and deflects it towards low pressure, and there would be no weather without friction impacting airflow.
High pressure and low pressure systems air flow directions (southern hemisphere)
High pressure (anticyclone) - Anticlockwise
Low pressure (cyclone) - clockwise
Vertical air flow in high/low pressure systems
High - divergence
Low - convergence
Airmass
A large body of air whose physical properties (temperature, moisture content and lapse rate) are uniform horizontally for hundreds of km.
Three factors that determine the uniformity of an airmass
- The nature of the source area where the airmass obtained its original qualities
- The direction of movement and changes that occur as an airmass moves over long distances
- The age of the airmass
Two airmass classification factors
- Temperature (arctic, polar, tropical, equatorial)
- The surface type in their region of origin (maritime or continental)
Mid-latitude synoptic weather sysytems develop in a
Heterogeneous atmospheric environment - large variations in airmass characteristics
In the southern hemisphere, westerly winds lie where
Between the subtropical highs and southern ocean lows
Frontogenesis
The origin of fronts in the mid-latitudes, caused by the the interaction of air masses of contrasting temperatures.
Where does warm and cold air flows originate
Northerly and southerly flow
Fronts are characterized by air-mass discontiniuty, with differences in
- Temperature
- Wind speed
- Pressure gradient
- Air density
Vertical motion occurs along the front due to
Surface convergence and upper level divergence
Cold air generally undercuts the warmer air because the warmer air
Is more bouyant
Four main types of fronts
- Warm front
- Cold front
- Occluded front
- Stationary front
Warm front
Occurs when an advancing warm air mass replaces cold air
Cold front
Occurs when an advancing cold air mass approaches a warm air mass, causing the warm air to rise much more quickly forming a steep frontal boundary
Occluded front
Occurs when a cold front catches up with a warm front, and the warm air mass wedged between them is lifted up (Occlusion).
Stationary front
Similar to cold front in structure, but neither warm or cold air mass dominates and doesn’t move.
Are warm or cold fronts faster and more intense
Cold fronts
Three phases of the frontal wave model - Cyclogenesis
Phase 1: Interaction of two different air masses that leads to frontal development and instability, with vertical motion and divergence of air at upper levels
Phase 2: Low level convergence, rising motion leads to rotation and initial development of cyclonic system.
Phase 3: Cyclone matures and have warm sector that is wedged between cold and warm fronts
The two main regions for the development of low pressure systems that affect NZ
- Southern ocean
- Tasman sea
Anticylones
Characterized by descending air leading to stable weather conditions
How do Anticyclones interact with depressions
Anticyclones tend to move slower than depressions (lows) and sometimes become stationary which can block the path of depressions
Why is anticyclonic blocking important
Because High pressure systems are associated with settled weather, and can be sources of: 1. winter cold 2. enhanced atmospheric turbidity/air pollution 3. fog and low level clouds (stratocumulus) 4. belts of strong winds can occur around their peripheries
