11.5 Static Stability and Vertical Soundings

Atmospheric “convection” broadly refers to

any local vertical motion of air due to buoyancy

Visible convection occurs when

convective clouds grow deep enough for a long enough time to produce precipitation and lightning

Conditional instability only becomes effective after

latent heat release begins to add buoyancy in clouds

The faster that temperature decreases with height ( steep lapse rate), the more….

unstable

Larger amounts of ________________ will give more instability

low level water vapor

Deep intense convective motions will usually originate from the…

lowest one or two kilometers

Vertical wind shear may contribute to

organization of severe convection

Common instability indexes that use temperatures and dewpoints from 800, 700, and 500 hPa

K index

Totals index

SWEAT index

Lifted index

the environmental temperature at 500 hPa minus the temperature of a parcel lifted to 500 hPa.

General categories for the choice of parcel to lift

the surface air

an average parcel over some depth

the top of a surface inversion when present

whichever level produces the most unstable result

Precipitable water (PW)

does not measure instability, but integrates the total water vapor in the column as if condensed into liquid form that can be used as a very rough guide to potential rainfall amounts.

The three ways to increase both instability and CAPE

Low-level warming

Upper-level cooling

Low-Level moistening

high base convection

Usually due to surface based convection in a relatively hot, dry environment so that air has to rise very high before condensing into cloud

Elevated convection

Convection from parcels that originate above a stable layer