Atmosphere

Atmosphere

The Atmosphere is composed of 78% nitrogen, 21% oxygen, and 1% other gases.
The earth's surface is heated by short wave solar radiation.

Calculate Cloud Base

[(Surface Temperature °C - Dewpoint °C) / 2.5] * 1000. Shortcut if all temperatures are in °C, (Surface Temperature - Dewpoint) * 400.

Lapse Rates

Saturated air cools less rapidly than unsaturated air because heat is released during the condensation of water vapour.

Dry

Unsaturated (less than 100% humidity) - 3°/1000'

Wet

Saturated (100% humidity) - 1.5°/1000'.

Standard Atmosphere

1.98°/1000'. Also called the environmental lapse rate.

Definitions

ISA

International Standard Atmosphere - Temperature at sea level is 15°C and the pressure is 1013.2hPa. The standard lapse rate is 2°/1000'.

Diurnal

Daily temperature change.

Troposphere

Part of the earth that contains all the elements of the weather.

Mesosphere

Region of the atmosphere between the stratopause and the mesopause.

Stratosphere

Temperatures in the lower stratosphere approximate those of the tropopause.

Ozone

A nearly colourless gas that is a very strong absorber of ultraviolet radiation and which is found at all altitudes in the atmosphere.

Coriolis Force

Force that is a result of the earth's rotation. It causes air in motion to deflect to the right in the northern hemisphere and to the let in the southern hemisphere.

Convection

Atmospheric motions in the vertical direction.

Convergence

Air that is being forced together into a smaller area Divergence is air being moved away or spreading out from an area.

Low Pressure Areas

Also called Depressions or Cyclones. Areas of MSL Pressure surrounded by higher pressure. They are marked by an L on surface charts. Ascending (rising) and convergence. Cloudiness and precipitation.