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B Relative Humidity 10 kilometers (6.2 miles) away...

  1. May 6, 2016 #1
    Hi, I'm reading about 50% relative humidity in my house about 10 kilometers (6.2 miles) away from the sea. How can water vapor from the sea reach me 10 kilometers away? I'm expecting zero or very low relative humidity.. does it mean if you live the ocean, you won't get relative humidity below 40% or 30%? How far from sea before relativity humidity drop to very low value?

    In a room.. what things can lower the humidity.. can opening electric fan blow the water vapors around the room or away?

    Thank you!
  2. jcsd
  3. May 6, 2016 #2
    There is no expected relative humidity value as a function of distance from the sea. For example, the Pole of Inaccessibility (the point furthest from the ocean) for the continent of South America is in the Brazilian rain forest, where the relative humidity is always very high! The water vapor in the air comes from evaporation of open water bodies, but also from transpiration of vegetation.

    As far as rooms go, many things can lower humidity. A simple fan cannot preferentially "blow away" water vapors, but you can get a dehumidifier or a desiccant, for example.
  4. May 7, 2016 #3


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    You're confusing the atmosphere with something that is static. Evaporation takes place over large bodies of water, like seas and oceans, and winds move the air and the water vapor around over the surface of the globe. Some of the water vapor will be held close to the ground; additional water vapor collects into clouds, which are found at various altitudes.

    Some cities where you would expect low relative humidity, like Las Vegas, Nevada or Phoenix, Arizona, actually never drop below about 20%. For drier places than this, you must travel to some pretty inhospitable locations, like the Atacama Desert in Chile.
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