the significance of dry & wet adiabatic lapse rate in cloud formation
Dry adiabatic lapse rate is the decrease in
temperature of an unsaturated air mass in it's vertical movement through a
stable equilibrium atmosphere where temperature is decreasing @
1(degree)celcius/100m ascend.
Saturated adiabetic lapse rate is the decrease in temperature of a saturated
air mass in it's vertical movement through the atmosphere where the decrease in
temperature of a saturated air mass in it's vertical movement through the
atmosphere where temperature decreases @ 0.4(degrees)C - 0.9(degrees)C ascend.
At the altitudes SALR(Saturated Adiabetic Lapse Rate) has no independent existence
in the sense that SALR=DALR(approximately)which is due to the fact that SALR
depends on water vapour concentration & temperature.
When condensation takes place in a air parcel undergoing DALR,esults in
decreased temperature due to expansion of air parcel since ENVIRONMENAL LAPSE
RATE (ELR) is less than the DALR & emergence of SALR conversion air mass
from DALR to SALR results in instability resulting in updraughts as a result of
concentration of water vapour droplets increase in the zone above line of
condensation.
The water vapour
droplets increase in the zone above the line of condensation level.the
increased concentration can be attributed to the fact that after the heat loss
due to condensation the water vapour particles contracts & it's density
increases & the number of condensation nuclei becomes relatively more than
the water vapour particles making the air mass more saturated.thus,air mass undergoing
DALR has limited capacity for vertical process(like mountains or a front)
initiates the displacement or if the equilibrium is restored just above the
dew-point level,& will result in the development of cumulus humilis clouds shallow,
fair weather cloud with distinct flattened tops).
While air parcel
undergoing SALR will form high altitude clouds.During absolute instability ELR
is greater than both SALR & DALR,at 300m.The parcel rises to until 7500m.
forming cumulus congestus.Thus,in the end it should be conclude that the difference
between DALR & SALR results in formation of various cloud types varying both in depth as well as
in their height of formation(layering of clouds at different altitudes).for
example:- if displaced warm air is associated with absolute stability then
cloud development is restricted to less than 3000m. & stratocumulus clouds
are more common. This difference also influence the precipitation regime in
different region.
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