Measurements · Meteorology
Absolute Humidity
Absolute humidity is the amount of water vapor actually in the air, independent of temperature; relative humidity, by contrast, says how close the air is to saturation at its current temperature.
What it is
What is absolute humidity?
Absolute humidity is the amount of water vapor actually in the air, independent of temperature; relative humidity, by contrast, says how close the air is to saturation at its current temperature. On this platform it is a weather-station reading, reported alongside relative humidity and dew point by the instruments that carry a humidity sensor.
It comes from the Airmar WeatherStation instruments. These are compact ultrasonic multisensors with no moving parts, measuring wind, barometric pressure, and air temperature in one housing; an optional, field-serviceable humidity module adds relative and absolute humidity, dew point, and heat index. Absolute humidity is therefore reported only by models that have the humidity module: the 110WX, 110WXS, 120WX, 150WX, 150WXS, 150WXRS, 200WX, 220WX, and 300WX. The 120WXH, 220WXH, 200WX-IPX7, and 300WX-IP67 have no humidity sensor and do not report it.
How it is measured
How Absolute Humidity Is Measured
An Airmar WeatherStation streams NMEA 0183 sentences, and connects to a Thiamis gateway over RS-232. Absolute humidity arrives in the WIMDA "meteorological composite" sentence (a single message that also carries barometric pressure, air temperature, relative humidity, and dew point), so the whole set is logged together. Wind arrives in its own sentence alongside.
An instrument on Thiamis1
A third-party instrument connected to a Thiamis gateway, reporting into the same Environet account.
Every device and option that measures Absolute Humidity 1
| Device / option | Type | Base platform | Measures |
|---|---|---|---|
 Airmar · 110WX, 110WXS, 120WX… | Weather Stations | Thiamis |
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Questions
Absolute Humidity FAQ
Which Airmar models report absolute humidity?
Those with the humidity module: the 110WX, 110WXS, 120WX, 150WX, 150WXS, 150WXRS, 200WX, 220WX, and 300WX. The 120WXH, 220WXH, 200WX-IPX7, and 300WX-IP67 have no humidity sensor.
How does it reach the platform?
In the WIMDA NMEA 0183 sentence, which also carries barometric pressure, air temperature, relative humidity, and dew point, read by a Thiamis over RS-232.
How is absolute humidity different from relative humidity?
Absolute humidity is the water vapor actually present in the air; relative humidity is how close the air is to saturation at its current temperature. The Airmar humidity module reports both.
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