Atmospheric Stability and Weather Systems

Flashcards covering key vocabulary and concepts related to atmospheric stability and weather systems.

Atmospheric Stability

The measure of how resistant an air parcel is to vertical motion.

Stable Air

An air parcel that, when displaced vertically, returns to its original position.

Neutral Air

An air parcel that, when displaced vertically, remains in its new position.

Unstable Air

An air parcel that, when displaced vertically, accelerates away from its original position.

Dry Adiabatic Lapse Rate

The rate at which an unsaturated air parcel cools as it rises, approximately 10°C per km.

Moist Adiabatic Lapse Rate

The rate at which a saturated air parcel cools as it rises, varying from about 6°C per km to 4.6°C per km depending on the altitude.

Pressure Gradient Force (PGF)

The force that results from changes in pressure across a surface, driving the movement of air.

Coriolis Effect

The apparent deflection of moving air due to the rotation of the Earth, which varies with latitude.

Hydrostatic Balance

The balance between vertical pressure gradient force and gravity in a fluid.

Geostrophic Balance

The balance between horizontal pressure gradient force and Coriolis force in the atmosphere.

Lifted Condensation Level (LCL)

The height at which an air parcel becomes saturated and condensation begins.

Convergence

The process by which air flows together at a point, leading to rising air and potential cloud formation.

Divergence

The process by which air flows apart, leading to sinking air and possible clearing skies.

Cold Front

The boundary where a colder air mass replaces a warmer air mass, often associated with storms.

Warm Front

The boundary where a warmer air mass overtakes a colder air mass, usually resulting in lighter, steady precipitation.

Stationary Front

A front that is not moving significantly, leading to prolonged periods of precipitation.

Occluded Front

A front that occurs when a cold front overtakes a warm front, often leading to complex weather patterns.

Dry Line

A boundary that separates moist air from dry air, commonly found in the Great Plains and associated with thunderstorms.

Jet Stream

A fast-flowing river of air found at high altitudes, influencing weather patterns.

Environmental Lapse Rate (ELR)

The rate at which temperature decreases with an increase in altitude in the atmosphere.

balance between the vertical PGF and gravity

hydrostatic balance

dry adiabatic lapse rate

10C/km

when the ELR is 12C/km the air is

absolutely unstable

the lower atmosphere typically has an elr of about 7C/km which is

conditionally stable

above the LCL air will cool by the

WALR

which force acts to move air horizontally from rest

pressure gradient

where do we find winds that are very close the geostrophic balance

in the jet streams

if an air parcel is lifted and the same temp as the environment it will

neither rise or fall

what is not a common way air is lifted

radiative cooling

air moving out of a surface high will move (in the N. Hemi)

outward in a clockwise motion

release of latent high will lead to strengthening a

surface low cyclone

due to curvature of the pressure gradient wind speed at the base of a trough will be

subgeostrophic

jet streak will cause convergence in their

left entrance and right exit

curvature and jetstreaks will lead to a surface low forming in the area of greatest divergence which aligns with the

left exit region

in which front is a colder air mass not responsible for the lifting of a warmer air mass

dry line

provided the conditions of the lifted air mass is unstable, which front will not produce thunderstorms

warm front

which front would pass with little change in temperature and moisture at a surface station

upper level

why don’t cold fronts always produce thunderstorms

the lifted air needs to be very moist