| Term |
Explanation |
| Above
Mean Sea Level (AMSL) |
Any
height above the mean sea level. See: Mean Sea Level
below. |
All
Time Records -
Record High Temperature |
Highest
temperature recorded during 1 day |
All
Time Records -
Warmest Day |
Highest
averaged temperature in a 12 hour period (6am - 6pm) |
| Aphel
(aphelion) |
Farthest
from the sun |
| Apogee |
Farthest
from the earth |
| Barometer
corrected to MSL |
Adjustment
made to allow for the height the barometer is above MSL |
| Base
18 degrees/degree days |
How
many days the temperature was below 18C (65F). See: http://www.energylens.com/articles/degree-days
for a fuller explanation. |
| Cloud
base |
Lowest
level of visible cloud or the height at which clouds may form |
|
Dew point |
The
temperature point at which air is cooled causing water vapour to condense
out into water |
| Dry
bulb thermometer |
Ordinary
thermometer. See: wet bulb thermometer below. |
| Humidity |
The
amount of water vapour in the air |
| Mean
Sea Level (MSL) |
Mean
sea level (MSL) is the average (mean) height of the sea, with reference
to a suitable reference surface. Defining the reference level, however,
involves complex measurement, and accurately determining MSL can prove
difficult. See: Wikipedia
explanation |
| Moon
– age |
How
many days into the lunar phase, i.e. since last new moon |
| Moon
– new |
Beginning
of a new lunar phase (no moon visible with naked eye) |
| Moon
– first quarter |
Half
the moon is visible (right side if in northern hemisphere) |
| Moon
– full |
Whole
moon visible |
| Moon
– last quarter |
Half
the moon is visible (left side if in northern hemisphere) |
| Perigee |
Nearest
to the earth |
| NOAA |
National
Oceanic and Atmospheric Administration |
| Perihel
(perihelion) |
Nearest
to the sun |
| Precipitation |
The
falling to earth of any form of water (rain, sleet, snow, mist or
hail) |
| Temperature
– apparent |
What
the temperature actually feels like taking into account temperature,
wind and humidity, e.g. if it's windy it will feel colder than the
measured air temperature. |
UTC
(Coordinated Universal Time) |
In casual
terms GMT (Greenwich Mean Time) and UTC are considered the same. |
| Wet
bulb thermometer |
A thermometer
that has its bulb wrapped with a wet muslin covering. A wet bulb temperature
will be lower than a dry bulb due to the effect evaporation. See:
Wikipedia
explanation |
| Windrun |
Product
of wind speed and time. For example, if the wind had been blowing
at 2 m.p.h. for 6 hours that would give a windrun value of 12 miles |
| Wind
chill |
Cooling
effect of exposed skin caused by the wind |
