Midterm I Flashcards
slides 1-8
What is Latent Heat?
energy absorbed or released during the phase change of water without a change in temperature
cooling: energy is taken from the surrounding environment during melting, evaporation, and sublimation
warming: energy released to the surrounding environment during condensation, freezing, and deposition
Why does Condensation of water result in the release of Sensible heat?
During condensation, water vapor turns into liquid. As water vapor the molecules contain high potential energy, when it condenses into a liquid state it loses energy in the transition, the lost energy is released into the surrounding environment as sensible heat because it increases the temperature of the surrounding environment
Difference between Advection and Convection?
Advection: horizontal transfer of air
Convection: vertical transfer of air
What is the Planetary Boundary Layer?
lowest part of the atmosphere (1-2 km) which is affected by turbulence produced by frictional drag from the earth’s surface
- strongly influences wind and turbulence
- thicker during the day & thinner at night
What Two kinds of air Movement/Disturbance affect the air motion in the Planetary Boundary Layer?
Turbulence: caused by surface roughness & friction
Convection: caused by solar heating & creates vertical mixing
What causes Turbulence in the Turbulent Surface Layer?
Surface friction: buildings, forests, terrain
Wind shear: variation in wind speed with altitude
Daytime heating: causing convective mixing
Difference between Free Convection and Forced Convection?
Free: caused by buoyancy
Forced: caused by surface roughness
Why is it generally Windier during the Afternoon than at Night?
Daytime heating encourages vertical mixing from turbulence,
bringing high speed winds from upper atmosphere down to the surface
At night, cooling reduced turbulence, weakening winds
Why are Infrared sensors on satellites used to identify the location of Clouds more often than Visible light sensors?
Infrared sensors can detect cloud without the presence of visible light, detecting clouds day or night
Visible light sensors can only detect the cloud with the presence of a light source, like the sun- so only during the day
Why is the Warmest time of the day not at Solar Noon?
This is because the earth is always releasing radiation even when it is not receiving much radiation (at night). In the morning the temperature begins to increase when the incoming radiation overcomes the outgoing radiation, it reaches the warmest time of day once the incoming radiation equals outgoing radiation, and then begins to cool off again
How and Why do patterns of air temperature in Winnipeg throughout January and July look different?
(besides literal temp. differences)
January: the temperature pattern is cold and relatively stable due to short daylight & low sun angles
July: the temperature pattern is hotter and relatively unstable with greater fluctuation, and has strong convection due to longer daylight & more intense sun angles
What does Vapor Pressure measure?
Vapor Pressure measures the pressure exerted by water vapor molecules in the air
More moisture = higher vapor pressure
Why is the Saturation Vapor Pressure over Water higher than the Saturation Vapor pressure over Ice?
(at the same temp.)
Air over water can hold more moisture than over ice
- water vapor escapes easier than ice
What does Saturation (of water vapor in the air) mean?
The air is holding as much water vapor as possible at the given temperature
What is the difference between Mixing Ratio and Specific Humidity?
Mixing ratio: grams of water vapor for every kg of dry air
Specific humidity: grams of water vapor for every kg of air
What is Absolute Humidity?
mass of water vapor per cubic meter of air
- changes with air volume
What is the Dewpoint Depression and how does it relate to Relative Humidity?
Dewpoint Depression: air temperature - dew point temperature
- difference between temp. & dewpoint temp.
- smaller difference = higher relative humidity
Why is there an Inverse Relationship between Air Temperature and Relative Humidity?
Warmer air holds more moisture
Increase temp. but not moisture, relatively less moisture compared to its potential capacity
What is the concept behind a Torricelli Barometer?
mercury dish + tube
the air pressure pushes the mercury up into the tube to indicate the atmospheric pressure
What is this equation used for and why?
Pmsl = Pstn x exp^( (g x Zstn) / (Rd x Tv) )
What is the effect of higher/lower z values on the calculated pressure (ignoring the other variables)?
To calculate atmospheric pressure changes with height
- reduction to sea level
- higher value of z = lower pressure
- lower value of z = high pressure
Difference between Isobar and Isohypse?
Isobar: line of pressure on a weather map
Isohpyse: line of height on a pressure map
Difference between an Isobaric Map and a MSL Map?
Isobaric Map: constant pressure with varying heights (isohypses)
MSL Map: adjusts surface pressure to the mean sea level equivalent (isobars)
How is the 1000-500 mb thickness map used to assist in forecasting of where on a map it may rain vs snow? What is the basis of this process? What is the Critical Thickness used for this purpose?
Thicker = Warmer because air expands
Thinner = Colder because air shrinks
Rain >5400 m & Snow < 5400 m
How is the 1000-500 mb thickness map used to assist in identification of Arctic and Tropical air masses? What is the basis of this process? What are the associated thicknesses?
Thicker = Warmer because air expands
Thinner = Colder because air shrinks
Arctic air mass < 5100m & Tropical mass > 5700m
How is the 100-500 mb thickness map used to indicate the location of the jet stream (at 500mb)? What is the basis of this process?
An intense pressure (thickness) gradient = jet stream
Faster winds occur with strong temperature gradients
Under what circumstances would you use this equation to calculate the Pressure Gradient Force?
PGF = - (1/p) x (ΔP/Δd)
Pressure differences on a constant heigh map
eg. MSL Map
Under what circumstances would you use this equation to calculate the Pressure Gradient Force?
PGF = - |g| x (Δz/Δd)
Height differences on an isobaric chart
eg. 500 mb isobaric chart
What factors affect the magnitude of the Coriolis Force? How?
latitude & windspeed
CF is stronger at higher latitudes or where the windspeed is faster
Explain how each component in this equation affects the speed of the geostrophic wind
Vg = (ΔP/Δd) x (1/ p x fc)
PGF: drives wind high to low pressure
Coriolis Force (CF): deflects wind, balancing PDF to create geostrophic flow
Wind speed increases when PGS increases or Coriolis force strengthens
