Re: humidity testing?? /CHRIS

[Guest guest]

Was it the post about dewpoints? I know about

that. Gauges would not give you dewpoint. How

long ago was it? I have not been able to read

much in the last week since my computer died!!!

....so I have to access email at library, etc

until I buy another one. I'm looking at ads for

them.

--- Tazin Round <unitedstatesvet@...>

wrote:

> If you can look his post up or ask him to

> repost it it was VERY interesting. I even

> bought a whole weather station to make sure I

> was

[Guest guest]

Hi

Okay. I did read this description by Carl.

Thanks. Anyway, I'm not clear if Accu-Rite

humidity gauges tell Relative Humidity or Actual

Humidity but I thought RH. I thought actual

humidity *was* dewpoint but??

Here is link to them. I have this type and like

them:

Here is link to it:

<http://www.natlallergy.com/prod/1526/acu-rite-humidity-monitor-thermometer.html\

>

--- Tazin Round <unitedstatesvet@...>

wrote:

> If you want dewpoints you need one of these

> weather stations. Look up

> www.lacrossetechnology.com/2310

> That is the model I have but they have others

> also. Here is the information Mr. Grimes posted

> previously.

>

> We tend to think of relative humidity (RH) as

> the amount of moisture

> in the air. The more moisture the more humid,

> right? But RH isn't

> just the amount of moisture, it is actually a

> comparison (by

> percentage) of the amount of moisture in the

> air to the temperature

> of the air. That's why it is called " relative "

> because the number is

> relative to the temperature; it changes with

> the temperature. You can

> have the same amount of water but a different

> RH at a different

> temperature. Likewise, you can have the same RH

> but the amount of

> water vapor will be different at different

> temperatures.

>

> Because...

>

> Hot air can hold more water than cold air. As

> the temperature goes up

> the percentage goes down. Likewise, as the air

> gets cooler it can

> hold less water so the percentage goes up. In

> fact, if you cool the

> air enough, the percentage will increase to

> 100%, which means it

> can't hold any more moisture - this is when it

> begins to rain. The

> temperature where this happens is called the

> dew point. Increase the

> temperature back above the dew point and it

> will stop raining because

> the warmer air can now hold the amount of water

> vapor that is in the

> air.

>

> The actual amount of water vapor in the air at

> any given time is

> called the Specific Humidity, because it

> doesn't change. It isn't

> " relative. " Relative Humidity does change

> because it is actually the

> comparison of Specific Humidity (amount) to the

> temperature. Which

> means the only way to directly compare the RH

> in two locations is if

> both are at the same temperature.

>

> Which brings us to your house. The temperature

> outdoors and indoors

> is not the same, so we can't simply compare the

> RH of each.

>

> In fact, 20% RH at 103 degrees calculates to

> 70% RH at 64 degrees, a

> reasonable temperature for your a/c.

>

> Because a/c cools the air at the coils to below

> the dew point, some

> of the moisture will be removed. Without

> getting into another

> description that is even more complex, just

> understand that the 103

> degree air can start with an RH higher than

> 20%, have some moisture

> removed by the a/c, and you are still at 70% RH

> inside.

>

> On Aug 15 <barb123> posted some excellent

> information including an

> article written by Dave Dombek at accuweather.

> com. (reprinted below).

>

> Carl Grimes

> Healthy Habitats LLC

>

> --------accuweather --------- -

> Dew point is simply the saturation point of the

> air, or the

> temperature to which the air has to be cooled

> in order to get

> condensation. It is really a true measure of

> how much water vapor is

> in the air...the higher the dew point, the more

> water there is in

> the air, and the lower the dew point, the drier

> the air mass is. In

> the summer, dew point is an excellent tool to

> use in determining how

> comfortable, or uncomfortable, it feels

> outside. Here is a general

> summertime guideline for dew points...

>

> Below 50: very dry

> 50-59: comfortable

> 60-64: moderately humid

> 65-69: humid

> 70-79: oppressive

> 80 and above: steam bath!

>

> Now you may be wondering... how does dew point

> relate to relative

> humidity? Well, the relative humidity is

> dependent on the

> temperature and the dew point. The closer

> together the dew point and

> temperature are, the higher the relative

> humidity is. The farther

> apart they are, the lower the relative humidity

> is. Here's an

> example of what I mean, and also an

> illustration why the term

> relative humidity does tell you anything about

> how comfortable or

> uncomfortable it is outside.

>

> Let's say we've got a very humid air mass in

> place, and the dew

> point is 70. It's daybreak, and it's very murky

> outside...hazy, and

> perhaps even foggy. The grass, car tops, etc.

> are all covered with

> heavy dew. Let's say the temperature at that

> time is 70 degrees.

> With a temperature of 70, and a dew point of

> 70, the air is

> saturated, and the RELATIVE HUMIDITY at that

> time is 100%.

>

> The sun comes up, burns off the fog and

> evaporates the dew. There is

> no front coming through that day...no air mass

> change whatsoever. So,

> the air mass will have basically the same

> amount of water vapor in

> it all day long, i.e., the dew point will stay

> close to 70. Now with

> the sun out, the air heats up, and the

> temperature rises. Let's say

> the high temperature that day, around 4pm, is

> 90 degrees. At that

> time, the hottest part of the day, the RELATIVE

> HUMIDITY is only

> 50%!!! That doesn't tell the average person

> anything about how it

> feels outside!!!

>

> The dew point is a good tool to use all year

> long. In the winter

> time, the lower the dew point, the drier the

> air mass is, and the

> more likely precipitation will fall as snow,

> even if the temperature

> initially is above freezing. That's because the

> air temperature will

> cool as the precipitation initially evaporates.

>

>

> The heat index is simply a combination of

> temperature and dew point,

> and how it feels. When the dew point is

> relatively low...say in the

> low 60s or lower, then the heat index is

> basically the temperature.

> However, as it gets more humid (higher dew

> point), then it feels

> hotter than the actual temperature. There

> really is something to the

> _expression.. . " it's not the heat but the

> humidity " . When the

> temperature is quite hot, and the dew points

> are very high, the heat

> index is extremely high. Sometimes the heat

> index can go into the

> dangerous category of 110 degrees or more.

>

> The Real Feel Temperature is something we

> developed in-house here at

> AccuWeather. It takes into consideration other

> factors besides just

> temperature and dew point. It factors in the

> time of day, the sun

> angle, and amount of cloud cover, the winds or

> lack thereof, etc.

> For example, a temperature of 90 and a dew

> point of 70 will feel

> worse at noon or 1 pm with the sun high in the

> sky than it will at 5

> pm or 9 am. Also, a temperature of 90 and a dew

> point of 70 will

> feel worse when it is dead calm than if there

> is

=== message truncated ===

[Guest guest]

The weather station looks interesting.

Dewpoints here in the midwest are 43%, pretty

nice right now.

--- Tazin Round <unitedstatesvet@...>

wrote:

> Ya, its all confusing to me as well, to beat

> all my dad is a meteorologist and I still am

> confused..lol

> I will go check your link out, thanks.

> Chris...

>

[Guest guest]

Any subterranean unheated/unairconditioned dark space will have some mold. It

may not be moldy or have as much mold as the interior or exterior or attic space

of a house but I have asthma and have yet to locate one in which I can breathe.

bbw <barb1283@...> wrote: The weather station looks

interesting.

Dewpoints here in the midwest are 43%, pretty

nice right now.

--- Tazin Round <unitedstatesvet@...>

wrote:

> Ya, its all confusing to me as well, to beat

> all my dad is a meteorologist and I still am

> confused..lol

> I will go check your link out, thanks.

> Chris...

>