- mass (kg) per unit volume (m^3) - near-surface air is denser than that above

AOS 3 Midterm Flashcards by HOPE CROSSLEY

Define the atmosphere

a mixture of gas molecules, small suspended particles of solid and liquid, and falling precipitation

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Compare weather and climate

Weather refers to the short-term phenomena.
Climate refers to the long-term patterns

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What is density

mass (kg) per unit volume (m^3)
near-surface air is denser than that above

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Define mean free path

average distance a molecule travels before colliding with another molecule.

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What is the relationship between density and kinetic energy?

proportional

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What is the ideal gas law

Pressure = Density x R x Temperature

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How are density and height in the atmosphere related?

the lower you are in the atmosphere, the higher the desnity

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How are pressure and height in the atmosphere related?

as you move down in the atmosphere, pressure increases

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Which thermal layer is where most weather happens?

Troposphere

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What are the ways heat can be transferred from one place to another?

Radiation (the sun heats the ground)
Conduction (the ground heats the air)
Convection (the warm air rises)

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What zones of air are clouds formed in/which are clear? What is the pressure for each?

Zones of rising air and low pressure = clouds form
Zones of sinking air and high pressure = clear skies

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PGF goes from ____ to _____ pressure.

high to low

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How does PGF relate to distance between isobars

PGF is inversely proportional to distance between isobars
Lines closer together = strong pressure gradient
Lines further apart =weak pressure gradient

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What angle does the PGF form with isobars?

90 degrees

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What is hydrostatic balance?

PGF = gravitational force

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How does heating a column of air affects its density?

Heating decreases density
so the column will contain the same amount of air but is less dense to compensate for its greater height

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What is the coriolis force?

produces an apparent deflection to the RIGHT in Northern hemisphere and LEFT in Southern
CF is zero at equator and increases with increasing latitude
increases with object it’s acting on’s speed
CF changes only the direction of object not its speed

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What is frictional force?

a force of opposition which slowed down air
matters when close to surface (within 1 mi)
friciton reduces wind speed so it also reduces CF

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What causes PGF?

differential heating of equators and poles

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What are cyclones and anticyclones?

Cyclones = enclosed areas of low pressure with roughly circular isobars (counterclockwise in N. hemisphere)
Anticyclones = enclosed areas of high pressure with roughly circular isobars (clockwise in N. hemisphere)

What are troughs and ridges?

troughs = elongated areas (low pressure)
ridges = elongated areas (high pressure)
pressure distributed as cyclones/anticyclones at surface and gradually give way to ridges and troughs in upper atmosphere

What is it called when going from solid water (ice) to gas water (water vapor)?

Sublimation
heat absorbed

What is it called when gas (water vapor) turns to solid water (ice)?

deposition
heat released

Describe evaporation

molecules escape from liquid into the overlying volume as water vapor
evaporation rate is proportional to the temperature of the liquid

Describe condensation

- water vapor molecules randomly collide with the water surface and bond with adjacent molecules - condensation rate is proportional to the "amount of vapor"

What are 2 ways to quantify humidity?

- **vapor pressure** (pressure exerted on the atmosphere by water molecules (mb) - **mixing ratio** (mass of water vapor in a unit mass of dry air (g/kg)

What is relative humidity

- amount of water vapor in relation to saturation point - highest RH in morning (coolest time) and lowest in afternoon (warmest time)

What is dew point temperature

temperature to which air must be cooled to reach saturation (without changing vapor pressure)

What are 3 processes that cause saturation

1) addition of water vapor 2) cooling the air to dew point (most clouds) 3) mixing cold air with warm moist air

What is homogeneous and heterogeneous nucleation?

- homogeneous nucleation: only water vapor molecules coming together to form water (effect or curvature, requires supersaturation so never rlly happens) - heterogeneous nucleation: water vapor molecules adhere to a solid surface (hygroscopic aerosols) on a condensation nucleus (cloud condensation nuclei - CCN)

What are the 2 types of processes that can change the temperature of an air parcel?

- diabatic processes: changes in temperature caused by **heat transfer** into our out of the air parcel (cooling air parcels to reach saturaiton) - adiabatic processes: changes in temperature or contraction due to **changes in pressure** (no heat transfer)

What is adiabatic lapse rate?

rate at which temperature decreases with increasing altitude

What is dew?

- liquid condensation on surface often occurring during the early morning hours - surface air becomes saturated and condensation forms on objects acting as a condensation nuclei

What is convection? What is buoyancy?

- convection = vertical motions caused by buoyancy - buoyancy = an air parcel that is denser than its environment sinks, while an air parcel that is less dense rises

What are the 3 types of equilibrium in the atmosophere?

1. Stable (ELR has smaller slope than DALR) (ball goes back - U shape) 2. Indifferent/neutral (ELR and DLR have = slope) (ball stays - flat) 3. Unstable (ELR has larger slope than DALR) (ball moves away - hill shape)

What is geostrophic balance?

PGF = CF

When does advection fog occur?

when warm air passes over a cool surface

When does saturation occur?

When the condensation rate = the evaporation rate

What is the LCL (lifting condensation level)?

The altitude at which clouds begin to form in a rising parcel of air

In which layer in the atmosphere is friction important in determining wind speed?

planetary boundary layer

When is the troposphere thickest?

the summer (when its warm)

What is the proportion for the dry adiabatic lapse rate (DALR)?

10 degrees per km

What is the proportion for the saturated adiabatic lapse rate (SALR)?

5 degree per km

What are the 3 basic types of clouds?

1. Stratus = Wide flat layer of clouds (stable ELR, no vertical motion) 2. Cumulus = Puffs/piles of clouds (unstable ELR, vertical motion) 3. Nimbus = Precipitating cloud (i.e. rain)

What is the prefix for high clouds above 19,000 ft?

- Cirrus - Mostly ice crystals - Wispy appearance (low water content)

What is the prefix for middle clouds between 6,000 and 19,000 ft?

- Alto - mostly liquid droplets

What is the prefix for low clouds below 6,000 ft?

- no prefix, just the base name - mostly liquid droplets

Are horizontal or vertical pressure changes bigger?

Vertical pressure changes are greater