Heat - The engine of the Atmosphere
In the section called "Where does the wind come from" we
described the effect heat from Solar Radiation has in generating
some of the wind forces we experience. Heat however also has other
effect on what we experience as weather.
Before we look in detail at some of the effects we should define
what is being displayed on the instruments and graphs above.
The heat energy of the air measured at 1.5 metres above ground
level by a sensor protected from the effect of radiation from other
sources; the sun, exhaust and ventilation ducts, etc. The protection
is usually afforded by the installation within a Stevenson Screen
located over short grass. This is to prevent the sensor from the
effects of reflected heat from other surfaces such as concrete or
The temperature of the air at a particular location at which
saturation occurs and water vapour begins to condense forming Dew.
Dew is commonly observed on the
leaves of plants in the early morning as shown in the
picture on the right
Measured as a percent of moisture in the air, relative to the
amount of moisture it can hold without precipitation at a given
temperature. Humidity (Absolute humidity) is a measurement of the
amount of water per unit volume of air.
The temperature of the ground measured at a given soil depth,
typically at 0 (Ground level), 10, 20 (This Station), and 30cm. Many
biological processes, including seed germination, plant emergence,
microbial activity, and soil respiration are dependent upon soil
The Atmosphere absorbs two kinds of energy, Kinetic; as a result
of the revolution of the planet, and Heat in the form of radiation
from the Sun. There two energies combine to create the dynamics of