Lecture 9: Humidity & Stability Flashcards
the heat exchanged between physical states of water provides more than ______ of the energy that powers the general circulation of the atmosphere.
30%
______ is the process by which ice changes directly to water vapour
Sublimation
______ is an important contributor to the shrinking of snowpacks in dry, windy environments.
Sublimation
True or False: Blowing snow enhances sublimation in the Canadian Rockies near Lake Louise, Banff National Park, Alberta.
True
The heat energy of a phase change is known as?
Latent heat
How many calories to change ice at 0°C to water at 0°C?
80
How many calories to change water at 0°C to water at 1°C?
100
How many calories to change water at 1°C to vapour at 100°C?
540
What is the latent heat of evaporation of 1 gram of water at 20°C?
585
True or False: evaporation can occur from a water surface at any temperature between 0 and 100 degrees Celsius and sublimation from an ices surface at any temperature below 0 °C.
True
When the phase change from liquid to vapour is induced by boiling, it requires the addition of 540 cal for each gram, this amount of energy is the ______.
latent heat of vaporization
When water vapour condenses to a liquid, each gram gives up its hidden 540 cal as the ______.
latent heat of condensation
In summary, the changing of 1 g of ice at 0°C to water and then to water vapour at 100°C—from a solid to a liquid to a gas—absorbs ______.
720 cals (80 cal + 100 cal + 540 cal)
The ______ absorbs 680 cal as a gram of ice transforms into vapour.
latent heat of sublimation
Water vapour absorbs ______, making it possible to distinguish areas of relatively high water vapour from areas of low water vapour
long wavelengths (infrared)
The amount of water vapour in the air is ______.
Humidity
_______ is a ratio (expressed as a percentage) of the amount of water vapour that is actually in the air compared to the maximum water vapour possible in the air at a given temperature.
Relative humidity
What is the equation for relative humidity?
Relative humidity = (actual vapor pressure in the air/max vapor possible in the air at that temp.) x 100%
What is the rate t which the evaporation and condensation reach equilibrium?
Saturation equilibrium
True or False: Warmer air = greater maximum water vapour possible
True
Saturation is also known as what?
100% Relative humidity
The temperature at which a given sample of vapour-containing air becomes saturated and net condensation begins to form water droplets is the ______.
dew point temperature
True or False: The air is saturated when the dew-point temperature and the air temperature are the same
True
True or False; Relative humidity is lowest in the early morning, when higher temperatures increase the rate of evaporation
False, lowest in late afternoon, a higher temperature increase rate of evaporation.
The share of air pressure that is made up of water-vapour molecules is ______.
Vapour pressure, expressed in mb (milibars)
True or False: For every temperature increase of 10 C°, the saturation vapour pressure in air nearly doubles.
True
Why do tropical storms occur in the tropics? And why is there no precipitation in the poles?
warm tropical air over the ocean can contain so much water vapor, thus providing much latent heat to power tropical storms.
because it contains too little water vapour, even though it is near the dew-point temperature
______ is the mass of water vapour (in grams) per mass of air (in kilograms) at any specified temperature
specific humidity
True or False: Specific humidity is affected by changes in temperature and pressure.
False, because its measure in mass, it is not
______ is the ratio of the mass of water vapour (grams) per mass of dry air (kilograms), as in g·kg−1.
Mixing ratio
______. is the maximum possible water vapour in a mass of water vapour per unit mass of air
Maximum specific humidity
______ is the mass of water vapour in grams per cubic metre of air
Absolute humidity
True or False: If air is cooled below its dew point, more condensation will occur than evaporation
True
What are the two forces that decide the vertical position of an air parcel?
upward buoyant force and a downward gravitational force
A parcel of lower density than the surrounding air is _____ and a parcel of higher density ______
buoyant, descends under the force of gravity
True or False: A parcel warmer then the surrounding air is more dense and a parcel colder then the surrounding air is less dense.
False, vice versa
______ refers to the tendency of an air parcel either to remain in place or to change vertical position by ascending (rising) or descending (falling)
Stability
An air parcel is ______ if it resists displacement upward or, when disturbed, tends to return to its starting place. An air parcel is ______ if it continues to rise until it reaches an altitude where the surrounding air has a density and temperature similar to its own.
stable, unstable
True or False: An ascending parcel of air tends to cool by expansion, responding to the reduced pressure at higher altitudes. In contrast, descending air tends to heat by compression
True
_____ means occurring without the loss or gain of heat.
Adiabatic
The ______ is the rate at which “dry” air cools by expansion as it rises or heats by compression as it falls.
dry adiabatic rate (DAR)
The ______ is a measure of the rate of temperature change with height in the atmosphere
environmental lapse rate
The ______ is the rate at which an ascending air parcel that is moist, or saturated, cools by expansion.
moist adiabatic rate (MAR)
Know the differences between stable and unstable parcels
If the ELR is somewhere between the DAR and the MAR, conditions are ______
neither unstable nor stable.
Know this to determine unstable and stable
____ is when the MAR and DAR are numerically smaller than the ELR, thus a dry or saturated air parcel is warmer than the surrounding air (ELR) and it will rise.
Unstable conditions
_______ occurs when the MAR and DAR are numerically larger than the ELR, thus a dry or saturated parcel of air is cooler than the surrounding air (ELR) and will tend to fall.
Stable conditions
______ occurs when the ELR (temperature profile of the surrounding air) plots between the MAR and DAR. Thus, under some circumstances moist or saturated air is warmer than the surrounding air and will rise (unstable), while dry air is cooler than the surrounding air and will fall (stable).
Conditionally unstable
Know the answers to these 2 questions: Maybe short answer.
If air rises vertically in the atmosphere, what happens to its temperature and relative humidity?
If air is unstable, and rises and becomes saturated and clouds begin to form, what types of clouds might that tend to develop?
