test 2 Flashcards
How much freshwater is present on earth?
2.78% (Most of that is ice and glaciers)
What is deposition? sublimation?
deposition: water vapor to ice
sublimation: ice to water vapor
What is humidity?
water vapor in the atmosphere.
what is an air parcel?
an air sample taken from the atmosphere
what are the physical controls on absolute humidity (3)
changes in air volume associated with air convection, air subsidence, and surface temperature changes
maximum specific humidity
the warmer the temperature, the greater capacity for the air to hold moisture
Vapor pressure
the increase in air pressure due to water vapor in the atmosphere..because of this, vapor pressure=high amounts of water vapor in the air
saturation vapor pressure
this is the maximum amount of water that can be present in the atmosphere before condensation starts taking place
Saturation point
This is reached when the actual vapor pressure and saturation vapor pressure are the same. In other words, when e=es relative humidity is 100%
what is dew point temperature
refers to the lowest temperature that can be reached before condensation takes place
What would maximize the chance of getting dew in the morning?
- strong radiational cooling..meaning the sky must be clear and the wind needs to be calm.
- moist air at sunset
When would you get dew vs frost?
dew: saturation is above freezing point
frost: saturation happens below the freezing point
foreign objects attracting water vapor at the surface
grass blades, twigs, leaves
Dry haze
this occurs because of pollution and stable weather conditions
wet haze (damp)
frequently observed at seashores. consists of super small water droplets in the air
fog
forms by cooling or evaporation and mixing
Radiation fog
More common in late fall and winter. Produced by earths radiational cooling.
ingrediants:
- Long clear night to allow a strong ground emission of LW
- A considerable amount of moisture in the air (at sunset)
- Calm to light wind
- A terrain which allows cold air to drain downhill (i.e., valley fog)
Advection fog
caused by the transport of warm moist air over cooler surfaces. these happen a lot on the pacific coast during the summer
Upslope fog
happens because moist warm air travels up an elevated area. JUst like advection and radiational fog, cooling is taking place
Evaportion fog (mixing)
This happens during late fall when an inland lake is warmer than a cold air mass coming from north
when e>es ….?
fog takes place
what is …what is es?
e=actual vapor pressure
es= saturation vapor pressure (the max amount of water vapor that can be held in the air)
when is fog considered dense?
visibility has to be greater than .25 miles
Clouds based on height?
cumuilform
Clouds based on form?
stratiform
What are the 3 high clouds?
Cirrus, Cirrocumulus, Cirrostratus
What are the 2 middle clouds?
Altostratus, Altocumulus,
Cirrus clouds. What is their composition? Altitude? precipitation? characteristics?
composition: ice crystals
altitude: 16,000-43, 000 feet
prec: none reaching the ground
Characteristics: These clouds indicate the direction that the wind is blowing. They usually come with fair weather but indicate the weather could change in 24-48 hours
(high cloud)
Cirrocumulus. Composition? Altitude? precipitation? characteristics?
composition: ice crystals
altitude: 16,000-43,000 feet
prec: none reaching the ground
Characteristics: Indicates the presence of warm air. Weather could be changing within the next 24-48 hours
(high cloud)
Cirrostratus. Composition? Altitude? precipitation? characteristics?
composition: ice crystals
altitude: 16,000-43,000 feet
prec: none reaching the ground
Characteristics: indicates rain within the next 12-24 hours. (especially if halo is seen around the sun)
(high cloud)
What do all high clouds have in common?
made up of ice crystals, 16,000-43,000 feet. no precipitation reaching the ground
Altostratus. Composition? Altitude? precipitation? characteristics?
c: water
a: 6,500-23,000 feet
p: none reaching the ground
characteristics: associated with an incoming warm air mass over the region. If the cloud gets thicker, it indicates that it is getting closer to the ground and rain will take place within 6-12 hours
(middle cloud)
Altocumulus. Composition? Altitude? precipitation? characteristics?
c: water
a: 6,500-23,000 feet
p: none reaching the ground
characteristics: associated with an incoming warm front of air over a region. indicates that there could be thunderstorms in the afternoon if the clouds are seen in the morning
(middle cloud)
Nimbostratus. Composition? Altitude? precipitation? characteristics?
c: water
a: near the surface to 6,500 ft
p: continuous rain
characteristics: light to moderate continuous rainfall (or snowfall)
(low cloud)
Stratus. Composition? Altitude? precipitation? characteristics?
c: water
a: ground level to 6,500 ft
p: drizzle
Characteristics: Light drizzle. uniform cloud base. Associated with fog and low visibility
(low cloud)
stratocumulus. Composition? Altitude? precipitation? characteristics?
c: water
a: surface to 6,500 ft
p: occasional showers
characteristics: often appears at sunset
What are the 3 clouds with vertical developments
Cumulus humilis, Cumulus congestus, Cumulonimbus
Cumulus humilis. Composition? Altitude? precipitation? characteristics?
c: water
a: 3,200-6,500 ft
p: none
characteristics: usually there is fair weather with quite a bit of blue sky in between each cloud
(vertical development cloud)
Cumulus congestus. Composition? Altitude? precipitation? characteristics?
c: water
a: 1,900-13,00
p: Showers
characteristics: these can develop ahead of a cold front. Showers can always be generated, (Both moderate and heavy) and they can often lead to the development of cumulonimbus clouds
(vertical development cloud)
Cumbulonimbus. Composition? Altitude? precipitation? characteristics?
c: water
a: 1,900-40,000 ft
p: Moderate to heavy storms
characteristics: worst impacts includes lightning, tornadoes, strong wind gusts
What is Adiabatic?
describes the cooling and warming rates for a parcel of expanding air
What is adiabatic expansion?
An ascending parcel of air cooling
What is adiabatic compression?
An ascending parcel of air warming
Dry adiabatic lapse rate?
This is dry air cooling or warming. It happens when the air is not saturated 10/1000m
Wet adiabatic lapse rate?
The rate at which saturated air cools or heats up 5/1000m
Dew point lapse rate?
1.8/1000m
What is the environmental lapse rate?
ELR applies to NON rising air in which the temperature is measured at successively higher levels of the atmosphere with the help of a radiosonde
.
stable atmospheric conditions
Air subsidence
unstable atompsheric conditions
Air convection
Why would an air parcel start to rise above the ground?
Because it is warmer than the environment
As a cloud extends vertically, which atmospheric condition would prevent the cloud top from reaching a certain height?
x
What is an absolutely stable atmosphere?
How is it generated? Which weather outcome is expected under this atmospheric condition?
The air parcel has the same temperature as the environment at the surface, but the environment is warmer than the air parcel above the ground. The air parcel doesnt have anywhere to go. This causes anti cyclones and clear skies
What is a ground temperature inversion? How is it
generated? When is it most common and why?
It created a surface temperature inversion which prevents air parcels to rise aloft. Outgoing LW during the night warms up the lower atmosphere. The depletion of energy at the surface cools the ground. It is most common in the early morning hours
What is an absolutely unstable atmosphere?
How is it generated? Which weather outcome is expected ? which type of atmospheric lifting can take place with this?
Initally the air parcel has the same temperature as the envirnoment at the surface. The air parcel then rises above the ground because the environment above ground is cooler than the air parcel. Adiabatic cooling then takes place and precipitations are generated. Convective lifting
What is a conditionally unstable atmosphere? How is it generated?
This is the most frequent state of the atmosphere. The stability all depends on if the air parcel is dry or wet. If it is dry, the conditions are stable and there is no cloud development. If it is wet then clouds will form as the atmosphere is not stable.
What is a subsidence
inversion? How is it generated?
This refers to a stable layer of warm air in the atmosphere a couple thousand meters above ground
Surface heating and free convection
Air rises above the field because it is warmer than the surrounding environment. If convection motion takes place, clouds extend vertically and precipitation might eventually take place
orographic lifting
winds generate the ascent of air mass over a mountain range. Eventually saturation and condensation take place. leading to cloud development and precipitation on the windward side of a mountain range
warm front lifting
a warm and moist air front starts to glide gently on top of cold air. This causes nimbo-stratus clouds and continuous rain
cold front lifting
The warm air is forced upward by the invading cold air mass. Severe storms can be expected
convergent lifting
quick condensation and development of clouds with vertical extensions leading to intense precipitations. Happens near the ITCZ
What is the ITCZ
Inter-Tropical Convergence zone. A narrow area where the Trade Winds from both hemispheres are converging towards a region where surface air temperatures are hot and strong convection prevails.
what is the size of a typical cloud droplet?
20 microns. Which is about 100 times smaller than a typical raindrop
Equilibrium vapor pressure
This is when a cloud particle does not get any bigger or smaller because the water molecules condensing onto the droplet are exactly balanced by the evaporating molecules
When will cloud droplet sizes vary?
If the vapor pressure is not at equilibrium, it will either because bigger or smaller depending on if evaporation or condensation is taking place
What two effects allow cloud droplets to grow?
- The solute effect
2. The curvature effect
The solute effect
salt particles are dissolved by water and then further condensation is possible
The curvature effect
air is supersaturated (i.e., the air temperature is below the dew point and the relative humidity over 100%). This way, there is a surplus of moisture that can aggregate
to a spherical droplet.
terminal velocity of a raindrop?
a rain drop falls and picks up speed with each air molecule it encounters. Once it hits the speed of gravity it falls at a constant rate
Bergeron process
process where clouds extend upward into regions where the air temperature is well below freezing
deposition (Bergeron)
ice crystals turn to water vapor
aggregation (Bergeron)
ice crystals collide with other ice crystals. This forms snowflakes
Supercooled water droplets (Bergeron)
lose mass by evaporation and shrink.
accretion
supercooleld water droplets freeze and coalesce with ice crystals…this forms hail
Rain: Definition and characteristics. Make a distinction between rain and drizzle. What is virga? What is meant by scavenging effect?
- falling drop of liquid water larger than 500um (in diameter)
- Rain is more than 500um drizzle is less than
- virga is rain that never reaches the surface
- The scavenging effect refers to the fact that after a storm visibility is usually much better
Snow: Definition and characteristics. How do you get large soggy snowflakes? How do you get snow powdery snowflakes? Review the table on Snow Precipitations. Pay attention to specific characteristics associated with each variable.
- snow is snow
- moist air below the cloud and temps slightly above or below freezing temp under the cloud
- dry air below the cloud and temps way below freezing under the cloud
sleet:
Definition and characteristics.
freezing rain:
Definition and characteristics. Make a distinction between sleet and drizzle. What is meant by the depth of the freezing layer?
This is the same as sleet except for the fact that the freezing layer is too close to the ground so the water droplets don’t have time to turn to sleet. Instead it is ice.
Hail:
Definition and characteristics How is hail generated?
Which type of cloud is associated with hailstorms?
What is graupel?
-Water droplets are taken by updraft in the cloud and quickly go below freezing temperature
-Hail is produced exclusively by cumulonimbus (cb) clouds
-Graupel: Large frozen raindrops which can become
embryos for hailstones during thunderstorms.
standard rain gauge
funnel shaped collecter that measures the water. 10 inches of water in the tube is equal to 1 inch of rain.
tipping bucket rain gauge
The weight of the water tips the bucket at every .01 inch of rain
snow depth
callibrated stick
water equivilent to snow
This just means that an average inch of rain is equal to 10 inches of. The lighter the snow, the higher the ratio is (30:1) but the wetter the snow, the lower the ratio is. (6:1)
