atmospheric inversion

Question 1

what are the inversions types?

Answer 1

1. nighttime radiation inversion: calm clear night so the ground is the coolest
2. frontal inversion: cold air moves underneath the warm air as it is denser. usually in cold front
3. marine inversion: cool moist stable marine air moves over the land
4. subsidence inversion: the middle high level air subsidences, sinks, it then warms by compression –> a layer of warm dry stable air. (large scale motion, not localised –> dangerous)

Question 2

how does stability affects the growth of cumulus

Answer 2

absolute stable: cumulus humilis
conditionally unstable: cumulus congests (clouds stops forming when it reaches stable layer)
absolute unstable: cumulonimbus, stops when it reaches tropopause.

Question 3

level of free convection (LFC)

Answer 3

level when the air parcel temperature exceeds the surrounding air temp.
atmospheric convection is found in this level, parcel is free to rise.
the parcel was stable and became unstable.

Question 4

compare CAPE and CINH

Answer 4

CAPE: the maximal energy available the the rising air parcel
measure in J/kg, exist in conditional unstable conditions. stops when reaches tropopause (B+)
CINH: area where convection is prevented.
it is the energy that needs to be put into the parcel to reach LFC (B-)

Question 5

what is the CAPE needed for a thunderstorm

Answer 5

1000s.

on a typical day, the negative area is greater than the positive

Question 6

destabilising the atmosphere by mixing

Answer 6

• mixing by convection or turbulence –> convection promotes cooling at top and warming the bottom. therefore the temp decreases greater with height, increasing ELR.
• ELR > DALR and MALR, so instability is promoted.
• if ELR happens to lie between DALR and MALR, then it is conditionally unstable

Question 7

Destabilizing the atmosphere by lifting (dry)

Answer 7

• the unsaturated air parcel was initially absolutely stable. it is lifted/cooled dry adiabatically.
• the top bit of the air parcel expands more as p decreases with height –> cools the top parcel more –> lapse rate increases.
• the final lapse rate lies between the DALR and MALR –> conditionally unstable

Question 8

Destabilizing the atmosphere by lifting (moist)

Answer 8

• the parcel was initially at an inversion (absolutely stable).
• cold air is at the bottom–> saturated (as cold water hold less water, higher RH), and warm air is at the top –> unsaturated (warm air holds more water harder to reach saturation)
• the bottom cold saturated air cools with MALR and the top warm unsaturated air cools with DALR.
• the top cools quicker with DALR, causing the final lapse rate to be greater (really flat slope). this lapse rate is greater than DALR and MALR. therefore it is absolutely unstable
• this is convective instability

Question 9

how subsidence gives inversion

Answer 9

• this is the opposite of destabilising from dry lifting
• the layer was initially conditionally unstable. when it sinks, the top is compressed more, therefore it warms more then the bottom
• inversion is developed