Albedo

The ratio of the amount of electromagnetic radiation reflected by a body to the amount incident upon it.

Bar

The basic unit of pressure in the MKS system of measurements; equal to 10⁶ dyne per cm².

Baroclinicity

When contours and isotherms are out-of-phase, advection is occurring and the atmosphere is described as baroclinic. With baroclinicity, the axis of the weather system tilts with height.

Contours

A line of constant height on a constant-pressure surface (i.e., 850mb, 700mb, 500mb, etc.)

Dyne

The unit of force in the centimeter, gram, second (CGS) system of measurements.

Frontal lift

Mechanical lifting of the air caused by a frontal boundary.

Geostrophic wind

The wind that would result if there were a balance between the coriolis force and the pressure gradient force over a region.

Hydrostatic balance

The state of a fluid whose surfaces of constant pressure and constant mass (or density) coincide and are horizontal throughout.

Inversion

In meteorology, the departure from the normal decrease of temperature with altitude. Instead of the temperature normally decreasing with height, it increases.

Isobars

A line of equal or constant pressure; an isopleth of pressure.

Migratory

To move to another region.

Millibar

One one-thousandth of a bar; equal to the force of 1,000 dynes per square centimeter.

Nocturnal

Pertaining to, or occurring in, the night.

Orographic effects

Clouds produced by the lifting and subsequent condensation of water vapor due to mountainous or "hilly" terrain.

Perpendicular

A line or plane at right angles to another line or plane.

Physics

The science of the properties, changes, interactions, etc. of matter and energy.

Sling psychrometer

A piece of weather equipment in which wet- and dry-bulb thermometers are mounted upon a frame that is connected to a handle at one end by means of a bearing or a length of chain. The psychrometer is whirled by hand in order to provide the necessary ventilation to obtain the temperatures we use for dew point computations.

Thermodynamic processes

Processes dealing with the reversible transformation of heat into mechanical energy.

Virtual temperature

In a system of moist air, the temperature of dry air having the same density and pressure as the moist air.

BLC

Boundary layer convergence

BTU

British thermal unit

CAA

Cold-air advection

CCN

Cloud condensation nuclei

CeF

Centrifugal force

CFCs

chlorofluorocarbons

CGF

Contour gradient force

CoF

Coriolis force

FPS

Foot, pound, and second system of measurement

Fr

Frictional forces

IN

Ice nuclei

LFC

Level of free convection

LND

Level of nondivergence

MKS

Meter, kilogram, and second system of measurement

NCEP

National Centers for Environmental Prediction

NETWCZ

Near-equatorial trade wind convergence zone

NMC

National Meteorological Center

NVA

Negative vorticity advection

PFJ

Polar-front jet stream

PGF

Pressure gradient force

PVA

Positive vorticity advection

RH

Relative humidity

SI

Systeme International

STJ

Subtropical jet stream

WAA

Warm-air advection