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"Always Open" |
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Bath, Pennsylvania, U. S. A.
Charles A. Giannetta
"Meteorologist - Professor"
"N O T E"
All weather articles written by the author,
weather records for Bath, Pa. USA, graphs,
graphics, pictures, are copyrighted and are owned by the author.
If you make use of data from this site,
please make reference to the: Station Licensee: Virginia T. Giannetta.
Owner - Author: Charles A. Giannetta. Computer Consultant: Charles E. Giannetta
& This Web Site. Thank you.
Check out the "Giannetta Meteorological Society".
Picture of a "Sling Psychrometer" used to measure the wet and dry bulb
temperature for determining the relative humidity.
"Relative Humidity"
What is Relative Humidity and how do we obtain it?
Relative Humidity is one of several methods used to express the
water vapor content of the air.
It is the ratio between the amount of water vapor the air is
actually holding at a certain temperature and expressed in
percentage.
When the water vapor stays the same and there is and increase in
the temperature, there will be a decrease in the relative humidity.
The opposite occurs if the temperature is lowered. The relative
humidity will increase.
A relative humidity of 70% gives us a different feeling at 85
degrees than at 45 degrees. In the winter we heat cold dry air in
our homes and create relative humidities of the fiercest and driest
desert regions. The comfort range of humidity lies between 50 and
70%.
The relative humidity is not always 100% when it rains. Sometimes
rain falls from higher layers through lower layers of air,
and relative humidity reflects the moisture content of the lower
layer.
Relative humidity can be 100% whitout rain as in the presence of
fog which is mass of air cooled to condensation without precipitation.
The instrument used to obtain the relative humidity is called a "Psyhrometer". It consists of two thermometers. One called a dry
bulb and the second is called a wet bulb. The bulb of the wet bulb thermometer is encased in muslin or gause.
The wet bulb is then placed in water and the instrument is whirled
or ventilated with a fan. Evaporation of the water takes place: this
is a cooling process and the wet bulb will show a lower temperature
reading than the dry dry bulb temperature. Ther difference or spread
between the tow readings is checked against predetermined tables and provides us with the relatice humidity and dew point.
The larger the spread between the readings the drier the air is.
If the air is saturated the wet bulb will read the same as the dry bulb and the relative humidity will be 100%.
© 2001 Charles A. Giannetta
* * TOP OF PAGE * *
| Charles A. Giannetta |
|---|
"Meteorologist - Professor"
"N O T E"
All weather articles written by the author,
weather records for Bath, Pa. USA, graphs,
graphics, pictures, are copyrighted and are owned by the author.
|
|---|
Check out the "Giannetta Meteorological Society".
Picture of a "Sling Psychrometer" used to measure the wet and dry bulb
temperature for determining the relative humidity.
"Relative Humidity"
What is Relative Humidity and how do we obtain it?
Relative Humidity is one of several methods used to express the
water vapor content of the air.
It is the ratio between the amount of water vapor the air is
actually holding at a certain temperature and expressed in
percentage.
When the water vapor stays the same and there is and increase in
the temperature, there will be a decrease in the relative humidity.
The opposite occurs if the temperature is lowered. The relative
humidity will increase.
A relative humidity of 70% gives us a different feeling at 85
degrees than at 45 degrees. In the winter we heat cold dry air in
our homes and create relative humidities of the fiercest and driest
desert regions. The comfort range of humidity lies between 50 and
70%.
The relative humidity is not always 100% when it rains. Sometimes
rain falls from higher layers through lower layers of air,
and relative humidity reflects the moisture content of the lower
layer.
Relative humidity can be 100% whitout rain as in the presence of
fog which is mass of air cooled to condensation without precipitation.
The instrument used to obtain the relative humidity is called a "Psyhrometer". It consists of two thermometers. One called a dry
bulb and the second is called a wet bulb. The bulb of the wet bulb thermometer is encased in muslin or gause.
The wet bulb is then placed in water and the instrument is whirled
or ventilated with a fan. Evaporation of the water takes place: this
is a cooling process and the wet bulb will show a lower temperature
reading than the dry dry bulb temperature. Ther difference or spread
between the tow readings is checked against predetermined tables and provides us with the relatice humidity and dew point.
The larger the spread between the readings the drier the air is.
If the air is saturated the wet bulb will read the same as the dry bulb and the relative humidity will be 100%.
© 2001 Charles A. Giannetta
* * TOP OF PAGE * * |
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