WW2010
University of Illinois

WW2010
 
  welcome
 
> online guides
 
  archives
 
  educational cd-rom
 
  current weather
 
  about ww2010
 
  index

Online Guides
 
  introduction
 
  meteorology
 
  remote sensing
 
> reading maps
 
  projects, activities

Reading Maps
 
  introduction
 
  utc conversions
 
  temp conversions
 
> surface obs
 
  surface maps
 
  upper air obs

Surface Obs
 
  overview
 
  temperature
 
  weather
 
> dew points
 
  cloud cover
 
  pressure
 
  winds
 
  contours

User Interface
 
  graphics
> text

NOTE: We've guessed that you're not using a client that supports colored tables and have tried to compensate. Low graphics mode looks much better on clients that do... we recommend switching to Netscape 3.0 or Microsoft Internet Explorer.
.
Observed Dew Point Temperature
indicates the amount of moisture in the air

The value highlighted in yellow located in the lower left corner (in the diagram above) is the dew point temperature in degrees Fahrenheit. In this example, the reported dew point temperature is 58 degrees.


Dew points indicate the amount moisture in the air. The higher the dew points, the higher the moisture content of the air at a given temperature. Dew point temperature is defined as the temperature to which the air would have to cool (at constant pressure and constant water vapor content) in order to reach saturation. A state of saturation exists when the air is holding the maximum amount of water vapor possible at the existing temperature and pressure.

When the dew point temperature and air temperature are equal, the air is said to be saturated. Dew point temperature is NEVER GREATER than the air temperature. Therefore, if the air cools, moisture must be removed from the air and this is accomplished through condensation. This process results in the formation of tiny water droplets that can lead to the development of fog, frost, clouds, or even precipitation.

Relative Humidity can be inferred from dew point values. When air temperature and dew point temperatures are very close, the air has a high relative humidity. The opposite is true when there is a large difference between air and dew point temperatures, which indicates air with lower relaitve humidity. Locations with high relative humidities indicate that the air is nearly saturated with moisture; clouds and precipitation are therefore quite possible. Weather conditions at locations with high dew point temperatures (65 or greater) are likely to be uncomfortably humid.



weather
Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.

cloud cover