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Old 08-24-2013, 05:05 PM
 
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Dew point is the temperature at which moisture/water vapor condense from its gaseous state to its liquid state. In the morning that is commonly known as "dew"! Pilots know this: if the air temperature is very close to the dew point (typically we're interested in the area of the airport) there is likely to be fog, which makes sense since fog = a cloud that is touching the ground, and clouds are simply areas of condensed water vapor.
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Old 08-26-2013, 09:19 AM
 
Location: Brendansport, Sagitta IV
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When we moved from Minnesota to Great Falls, we sold our dehumidifier. We soon regretted that -- while the humidity is generally low, when it's not, it's stifling and sticky. And it doesn't take as much of it to accomplish that. As Elk says, dew point is probably part of it (I'm not sure why).

In the desert, where (even when it's barely 100 by the thermometer) the heat is so intense it's like being hit on the head, ANY humidity is stifling, and the numbers are deceptive -- 20% of the water vapor that very hot air can hold is still many times more than what cooler air can hold. That's why they call it relative humidity!
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Old 08-26-2013, 11:07 PM
 
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Quote:
Originally Posted by Reziac View Post
When we moved from Minnesota to Great Falls, we sold our dehumidifier. We soon regretted that -- while the humidity is generally low, when it's not, it's stifling and sticky. And it doesn't take as much of it to accomplish that. As Elk says, dew point is probably part of it (I'm not sure why).

In the desert, where (even when it's barely 100 by the thermometer) the heat is so intense it's like being hit on the head, ANY humidity is stifling, and the numbers are deceptive -- 20% of the water vapor that very hot air can hold is still many times more than what cooler air can hold. That's why they call it relative humidity!

Dew point has little to dew with it. (I couldn't help myself.). Humidity makes high air temperature miserable because your perspiration doesn't evaporate as easily in humid air as in dry air, hence your body feels cooler in the dry air where the evaporating perspiration carries away heat. That is also why your sweat beads up and stays on your skin in humid air and you feel sticky.
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Old 08-27-2013, 05:45 AM
 
Location: Spots Wyoming
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hmmmm. all about dew point.

Observed Dew Point Temperature: indicates the amount of moisture in the air
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Old 08-27-2013, 08:42 AM
 
Location: Brendansport, Sagitta IV
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So -- the saturation point is what we actually feel as "humid", rather than the relative humidity? That would explain San Francisco.
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Old 08-27-2013, 11:57 AM
 
Location: Spots Wyoming
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Quote:
Originally Posted by Reziac View Post
So -- the saturation point is what we actually feel as "humid", rather than the relative humidity? That would explain San Francisco.
Yeah, the way I understand it is that Relative Humidity is derived from Real Humidity/Dew Point. Like I said, I don't understand it, I just know that when dew point is high, regardless of humidity, it's miserable outside.

You are right about San Francisco. It's about as saturated as you can get. I was sentenced to 18 months there once.
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Old 08-27-2013, 01:17 PM
 
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Originally Posted by ElkHunter View Post

You're right! I'm wrong; there is a relationship. I was focused on the fact that dew point is a temperature; but I see it is influenced by (or influences) moisture content in the air.
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Old 08-27-2013, 10:16 PM
 
Location: Spots Wyoming
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Originally Posted by sky1949 View Post
You're right! I'm wrong; there is a relationship. I was focused on the fact that dew point is a temperature; but I see it is influenced by (or influences) moisture content in the air.
I still don't know, for sure, exactly what it is. I've never found anywhere where it explains it, other than vague "it influences" writeups.
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Old 08-27-2013, 10:43 PM
 
Location: Brendansport, Sagitta IV
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Originally Posted by sky1949 View Post
...since fog = a cloud that is touching the ground, and clouds are simply areas of condensed water vapor.
If fog rises off the river, is it still a cloud?
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Old 08-27-2013, 10:53 PM
 
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Quote:
Originally Posted by Reziac View Post
If fog rises off the river, is it still a cloud?
Well, I'm not a meteorologist, but I did stay at a Holiday Inn Express recently. I think the answer to your question is "no". I just have learned that a cloud and fog are the same thing, except the latter touches the ground. Now if a cloud were 6" off the ground, I think I'd still consider it, and call it, fog. But, if it were 7"...
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