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3.4.2.3.4.
Dew point (measured or calculated)
The dew point is the temperature at which dew forms and is a measure of atmospheric moisture. It is
the temperature to which air must be cooled at constant pressure and water content to reach conden-
sation. The dew point or will be issued (e.g. by the EOLOS IND or THP) or can be calculated from the
temperature and the measured air humidity.
3.4.2.3.5.
Absolute air humidity
The absolute air humidity (AH) or real humidity is the mass of dissolved water in a certain volume of
air. It is upwardly limited by the maximum air humidity.
3.4.2.3.6.
Air pressure (altitude corrected)
The air pressure can be issued directly or can be corrected in relation to the altitude of the measure-
ment location. Therefore, the altitude of the air pressure sensor (measurement location) has to be in-
serted und normally the measured temperature and the relative humidity is needed.
If there is no measured temperature and relative humidity the altitude correction will be calculated with
the ICAO-standard atmosphere.
According to the ICAO-standard atmosphere the relative air humidity is considered as 0 % (dry air)
and the temperature set to 15 °C (288.15 K). Up to 11000 m (m.a.s.l.) the (standard) temperature de-
creases by -0.0065 K/m.
3.4.2.3.7.
Air pressure above sea level - QNH
The measured air pressure can be corrected to sea level. For the simple correction according to QNH
the ICAO-standard atmosphere is used. The only requirement is to insert the to be considered height
of the air pressure sensor above sea level.
The QNH-calculation takes place with the global mean values in the mean sea-level of the ICAO-
standard atmosphere (relative air humidity = 0 % (e = 0), temperature = 15 °C).
3.4.2.3.8.
Air pressure above sea level - QFF
The QFF calculation takes places under the consideration of the real atmosphere at the measurement
site. Therefore, the to be considered hight of the air pressure sensor above sea level has to be in-
serted as well as to be assigned a temperature sensor and a relative humidity sensor.
3.4.2.3.9.
Sunshine duration (day)
The display of the sunshine duration takes place in hours minutes (HH:MM). Therefore, over the day
(starting at 0 o’clock) the measured status “sun yes/no” will be added up (integrated) and at 24 hours
reset again.
3.4.2.3.10. Duration of precipitation (day)
The display of the duration of precipitation takes places equivalent to the sunshine duration. The dura-
tion of precipitation takes place in hours and minutes (HH:MM).
Therefore, over the day (starting at 0 o’clock) the measured status “rain yes/no” will be added up (inte-
grated) and at 24 hours reset again.
3.4.2.3.11. Amount of precipitation (day)
The display of the amount of precipitation takes place in mm. Therefore, over the day (starting at 0
o’clock) the measured will be added up over the time (integrated) and at 24 hours reset again.
