The amount of water vapour in the air at any given time e.g 6 grams in a cubic metre of air.
Process by which water droplets stick with ice in a cloud causing the ice to become bigger. Responsible for hail formation.
Adiabatic Lapse Rate
This shows the rate at which an air parcel's temperature decrease if lifted or increase if it descends.
Adiabatic Temperature Change
Temperature changes occurring within an air parcel without the addition or subtraction of heat. Pressure changes are inversely proportional to temperature, high pressure => low temperatures, low pressure => high temperature.
When warm air parcels move along a cold surface causing them to be cooled to dew point temperature. Occurs mainly along coasts where differential heating of ocean and land exists.
A type of fog found along coasts formed when warm air parcels condenses along a cold surface.
A substance enclosed under pressure and released by a propellant gas such as aCFC as spray
Partially melted ice crystals with their liquid coating stick with solid ice crystals forming hexagonal snowflakes. Responsible for snow formation.
The reflectivity of a surface.
A large body of air whose characteristics temperature, pressure and humidity are acquired from source region and placed in the path of movement.
Height above sea level.
A middle level cloud with a white grey appearance and a layered puffy structure.
A uniform grey or bluish, middle level cloud that often covers the whole sky. A glimpse of the sun is seen. Drizzles are common with this type of cloud.
A warm air rising up a mountain.
An area of high pressure where winds converge at high elevations, descends and then diverge on the surface. Characterized by stable weather conditions.
A mixture of gases surrounding earth.
Abbreviated as CFC. An ozone depleting compound of chlorine, fluorine and carbon. Often used in refrigerants and aerosol propellants.
An uncommon high level cloud with thin broken ripples. Usually these clouds are remnants of cirrus or cirrostratus.
A high level cloud appearing as a milky white veil. Very thin and almost transparent and often producing a halo effect.
The highest level cloud with a wispy and feathery filament appearance. Mostly composed of ice crystals.
The prevailing weather conditions of a broad area over a given period of time (30-50 years).
When cold air moves in an area formerly occupied by warm air. See fronts
A process of rain formation where small water droplets collide and merge together forming bigger droplets which then split again to form rain droplets. See Rainfall Formation Theories
A process whereby water vapour (gas) changes into liquid.
Minute particulates such as dust and ash found in the atmosphere which where water vapour accumulate to form tiny water droplets.
This occurs when the environmental lapse rate is lower (cooling at a slower rate) than the DALR (cooling at a first rate) but higher than the saturated adiabatic lapse rate (cooling at a lower rate). See Stability and Instability
The transfer of heat through matter from high to low pressure.
The process by which air parcels are heated by the earth's surface causing them to become lighter, rises and cools.
A type of rainfall where air parcels are heated by the earth's surface causing them to become lighter, rises, cools and condenses producing towering cumulonimbus clouds with heavy rainfall.
A type of rainfall whereby two bodies of air usually originating from the sea rises together on a low pressure area usually over land.
A type of force caused by the rotation of earth which deflect winds in their direction of motion. Winds are deflected left in the Southern Hemisphere and to the right in the Northern Hemisphere.
A towering cloud of great vertical extent. These clouds begin at lower levels stretching all the way to higher elevations. Heavy rainfalls with hail are most common.
A middle to low level cloud with a cauliflower appearance that grows vertically. They have a bright sharp outline and dark flat base. Often these clouds are small replicas of cumulonimbus
System of winds that converge and rises on a low pressure area producing heavy rainfalls and unstable weather conditions.
A type of rainfall where moist air usually originating from the ocean rises cools and condenses producing heavy rainfalls on the windward side.
An oxygen molecule containing three oxygen atoms that is found in the stratosphere and is responsible for trapping the dangerous ultraviolet radiation from reaching the earth.See Ozone and Its Significance
A toxic smog formed when particulates in the atmosphere react with sunlight.
Any form of water deposition originate on or off the earth's surface.
The initial driving force of wind. Closely spaced isobars results in a steep (high) PGF thus high wind speeds while a weak PGF is caused by widely spaced isobars.
Earth's surface absorb solar radiation which in turn returns and heat the air above it.
The process whereby water droplets fall to the surface.
A type of frost were supercooled water droplets freeze on top of another on a freezing surface creating a feathery appearance of ice on the windward side.
Saturated Adiabatic Lapse Rate
The rate at which a wet (saturated) air parcel rises above the condensation level. The rate of cooling is 5oC/ 1000m which is lowered by the addition of latent heat released during condensation. See Lapse Rates
Sensible Heat Transfer
The transfers of heat by air parcels in and out of an area being observed.
A type of precipitation containing a mixture of snow and partially melted ice.
A mixture of fog and smoke.
A type of precipitation formed by aggregation containing hexagonal ice crystals (snowflakes).See Precipitation.
The second layer (going up) of the atmosphere characterised by high temperatures and ozone. The upper boundary is referred to as stratopause.
An atmospheric condition characterised by clear and stable weather conditions formed when the environmental lapse rate is lower (cooling at a slower rate) than the dry adiabatic lapse rate (cooling at a faster rate) causing the dense cold air parcel to sink.
The direct change of state from solid to gas.
The supply of heat that was trapped by the surface during the day to the surface at night.
Very cold water droplets below freezing point. These droplets tend to freeze instantly upon encountering a freezing object.
A low level grey cloud that expansively flattens in the atmosphere and produce light drizzles.
A low level, puffy and broken grey clouds that produce light to moderate rainfalls. May grow into nimbostratus.