Chapter 6 Stability and Cloud Development Flashcards
what are air parcels?
ballon-like balls of air that will rise/sink
-they rise, pressure lowers, parcel expands, it cools
-sink=compress and warm
what are adiabatic processes?
change in temperature without any exchange of heat with its surroundings
What is the dry adiabatic lapse rate?
rate of cooling of unsaturated air
dry rate= always 10 degrees C/1km
what is the moist adiabatic lapse rate?
rate of cooling in saturated air
moist rate= average 6 degrees C/1km
*always warmer than dry adiabatic air because saturated air condenses releasing latent heat
what does a bigger lapse rate mean?
bigger lapse rate=more cooling with height
What is unstable?
a parcel that is warmer/less dense than the environment around it, it will rise
what is stable?
a parcel that is cooler/more dense than the environment around, it will sink
what is an absolutely stable environment?
at every height the parcel is colder than the ENV, it will sink or stay in place
to make atmosphere more stable, we want environmental lapse rate to be small, cooling surface or warming aloft
does inversion create a stable or unstable environment?
inversion is the most extreme stable environment
what is subsidence?
sinking air creates an inversion, which acts as a cap on vertical motion, pollution is not diluted
what is an absolutely unstable environment?
at every height the parcel is warmer, it will rise
to make atmosphere more unstable, environmental lapse rate needs to be big
warming ground, cooling aloft
what is a conditionally unstable atmosphere?
moist lapse rate < ENV lapse rate <dry lapse rate
stable as long as air parcel stays unsaturated, BUT saturation brings on the potential for instability
what are the cloud formation mechanisms?
- surface heating and free convection
- uplift along topography
- widespread ascent due to convergence
- lifting along weather fronts
how does convection develop clouds?
differential and surface heating creates areas of higher surface temperature. air above warm land surface heats, forming a bubble of warm air that rises.
LCL= height where cloud forms
LFC= height where parcel is warmer than ENV
dew point lapse rate= 2 degrees C/1Km
how does topography create clouds?
orographic uplift as air goes up and over a mountain
