In extreme dry conditions when moist convection is just barely possible, cumulus clouds with very high bases form above the surface; below this high-based cloud layer there is a deep, dry adiabatic layer of microburst. In extreme wet conditions a deep, nearly saturated layer with a nearly moist pseudoadiabatic lapse rate forms that is topped by an elevated dry layer which is a cause of microburst.
In case of dry microburst the rain falls below the cloud base mixes with dry air from where it begins to evaporate and this evaporation process cools the air. The cool air descends and accelerates as it approaches the ground from where it spreads in all directions and the divergence of wind is the sign of a microburst. The wet microburst is accompanied by heavy rainfall at the surface which are warmer then the environment. This downburst pushes the downward acceleration of parcels that cause negative buoyancy which tends to drive dry microburst.
Wind shear is the difference in wind speed and direction over a short distance in the atmosphere. The extent and suddenness of a microburst accompanied with low-level wind shears are a cause of many fatal aircraft crashes; particularly they affect in landing and take-off phases.
The microburst is recorded to last no more then 15 minutes from the time they strike on the ground. ...Show more