GLOSSARY

Cold Advection The transport of relatively cold air by the wind.
Curvature Vorticity The component of the relative vorticity depending on the curvature of the streamlines.
Convergence The contraction of a two-dimensional wind field (u, v). Negative divergence.
Divergence The expansion of a two-dimensional wind field.
Height Contours at 1000, 500, ... hPa Countour lines of geopotential height above mean sea-level.
Isotachs Lines of equal wind speed
Negative Vorticity Advection The transport of absolute vorticity leading to less cyclonic/more anti cyclonic vorticity.
Vertical Motion (Omega) Vertical motion in terms of pressure.
(Isentropic) Potential Vorticity Vorticity which a column of air between two adjacent isentropic surfaces would have, if it were brought to an arbitrary "standard" thickness.
Positive Vorticity advection The transport of absolute vorticity leading ro more cyclonic/less anticyclonic vorticity.
Showalter Index The index of the likelihood of thunderstorm occurrence obtaines by finding the temperature which would be attained by ascent of the air from 850 hPa and substracting this from the actual air temperature at 500 hPa.
Thunderstorms become more likely when index is <+ 3.
Shear Vorticity The component of the relative vorticity.
Temperature Advection The transport of temperature by wind.
Thermal Frontal Parameter The change of temperature gradient in the direction of the temperature gradient.
(Equivalent) Thickness The thickness of the atmospheric layer between two pressure surfaces.
Potential Temperature The temperature that an unsaturated parcel of dry air would have if brought adiabatically and reversibly from its initial state to a standard pressure p0, typically 1000 hPa.
Equivalent Potential Temperature Similar to Potential Temperature, but for moist air.
Vorticity Advection The transport of absolute vorticity by the wind.
Vorticity The rotation of a two-dimensional wind field (u,v).
Warm Advection The transport of relative warm air by wind.
Wet Bulb Temperature The temperature an air parcel would have if cooled adiabatically to saturation and then compressed adiabatically to the original pressure in a moist adiabatic process.