Psychrometrics Reference Libraries

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Weather Model Discussion How To Use Surface Dew-points For
2013-01-29 08:53:47

Surface Dew-points can play a huge role in weather forecasting. The first such role is that it helps determine the amount of moisture in the atmosphere for a given point. If we look at the current dew-point map above from January 28, 2013 we can note several things of interest. First, if we look at where the black circle is around the number 70, we can make note that this air right off the...

Surface Map Features
2012-07-30 10:31:28

The map above shows our dew-point temperatures which is an important temp when it comes to weather. The dew-points help us determine how much moisture is in the atmosphere. If we look at the circle placed over Southern Mississippi we can see temps in the Mid 70’s. That is considered to be very saturated and humid type of weather. When you walk outside it feels very uncomfortable. While if we...

The Heat Wave Of The Central United States
2012-06-26 06:00:45

So why is there so much heat and humidity rising up into the Northern Plains creating a surge of hot weather? The answer is in the weather map above. If we look over Lake Michigan we see an area of High pressure which has a clockwise flow over the region. So places on the East are having cooler weather as they are getting the air from Canada pushing down towards them. North Dakota into...

Water vapor
2009-07-18 14:15:52

Water vapor (aqueous vapor) is the gaseous phase of water. It is one stage of the water cycle of our planet. Water vapor is formed from either evaporation or heating of liquid water, or from the sublimation of ice. In nature, water vapor is continuously produced by evaporation and removed by condensation. Along with carbon dioxide and methane gas, water vapor is one of the greenhouse gases....

2009-07-06 16:44:13

Haze is a type of atmospheric phenomenon where dust, smoke and dry particles in the air obscure the sky's clarity. Haze is created through various activities including farming, traffic pollution,and even wildfires. The World Meteorological Organization (WMO) categorizes the obscuration of the Earth's atmosphere by a list of different types of atmospheric phenomena. One of these is haze. The...

2009-07-06 16:36:49

Mist is a phenomenon that consists of small droplets of water suspended in air. Mist occurs as part of a natural weather event or from volcanic activity. Mist is most common in cold air above warm water. Mist also occurs when air is exhaled in cold temperatures or when steam is formed in a sauna. Aerosol cans can create artificial mist if the humidity levels are just right. The one...

2009-07-06 16:28:37

Condensation is the change of the physical state of matter from a gaseous form into liquid form. When the transition of matter happens from gaseous to solid directly, it is known as deposition. Condensation occurs when a vapor is cooled or compressed to its dew point. Water vapor that naturally condenses on cold surfaces into liquid is called dew. Water vapor will only condense on another...

White Frost
2009-07-06 16:20:02

White frost is a type of solid ice that forms directly from water vapor found in the air. White frost forms when the humidity is above 90% and the temperature is below 18 degrees Fahrenheit. White frost grows against the wind, since the facing winds have higher humidity than leeward air. The wind must be light or the delicate icy structures become broken. The structures have big, interlocking,...

Soft Rime
2009-07-06 16:09:35

Soft rime is a type of milky white ice that forms when water droplets in light freezing fog freeze to the outer surfaces of objects. This formation usually occurs with light winds or in calm conditions. The rime forms to the windward (side facing the wind) side of solid objects. Soft rime is similar in appearance to hoar frost, but is formed differently. Soft rime is formed when vapor first...

Hard Rime
2009-07-06 15:49:33

Hard rime is a type of white ice that forms when water droplets found in fog freeze to the outer surfaces of objects. Hard rime is most often found on trees atop mountains and high ridges in winter, when low clouds cause freezing fog. This fog freezes along the windward (sides facing the wind) side of trees, buildings, and any other solid objects. The air temperature needed for hard rime to...

Word of the Day
  • A large punch-bowl of the eighteenth century, usually of silver and with a movable rim, and decorated with flutings and a scalloped edge. It was also used for cooling and carrying wine-glasses.
  • A kind of cotton handkerchief having white spots on a colored ground, the spots being produced by a chemical which discharges the color.
This word is possibly named after Monteith (Monteigh), 'an eccentric 17th-century Scotsman who wore a cloak scalloped at the hem.'