Download Weather – the current atmospheric conditions

Weather Notes
Weather – the current atmospheric conditions
Factors which affect weather
1. TEMPERATURE – measure of molecular movement. Thermometer.... degrees
2. HUMIDITY -
the amount of water vapor in the air. Psychrometer... percentage
3. WIND – movement of air. Anemometer.... direction and mph range
4. AIR PRESSURE- weight of air. Barometer... inches of mercury or millibars
29.92 in
1013.25 mb
Relative Humidity – the percentage of saturation. Always a %. Describes how much water
vapor is in the air compared to how much water vapor the air can hold.
(test score)
Dew Point – the temperature at which water vapor in the air begins to condense
***Warmer air can hold more water vapor***
Measuring Humidity
Hair Hygrometer - human hair responds to water vapor in the air (bad hair day)
Psychrometer – Two thermometers
one has a damp cloth attached – wet bulb
the other has nothing attached – dry bulb
Evaporation – the wet bulb temperature drops because evaporation is cooling process. (sweating)
Clouds
Cloud Formation – clouds form when water vapor condenses around a nuclei
Cloud Seeding – spray silver iodine into the atmosphere. The water vapor condenses around the
silver iodine to form clouds.
Types of Clouds
Stratus – low clouds. Layered and far reaching
Cumulus – thick, fluffy, piled high. Middle altitude
Cirrus – thin, wispy, feathery. High altitude
Alto – high (prefix)
Nimbo – precipitation or rain
.
Fog – very low stratus cloud. May touch ground
Contrails – jet exhaust. Precipitation in day or two
Precipitation
Precipitation – any form of moisture which falls to Earth.
The type of precipitation is based on temperature
1. Rain – fall as liquid. formed by condensed water vapor or melted snow. Above Freezing
2. Snow – water vapor that sublimates directly into a solid. Below Freezing
3. Sleet – rain that freezes as it falls. Below Freezing
4. Hail – ice that falls to Earth. Only occurs during thunderstorms. Above Freezing
5. Freezing Rain – rain that freezes after it hits the ground. Above Freezing
32 degrees F – freezing
0 degrees C – freezing
Weather Symbols
Cloud Cover - clear, scattered, partly, mostly, completely overcast
Precipitation - rain, thunderstorm, snow, fog, sleet, hurricane
Isobar - a line that connects points of equal barometric pressure on a weather map
Isotherm – a line that connects points of equal temperature on a weather map
Air Masses
Air Mass – a body of air that has the same temperature and humidity through out.
Based on where it forms. (over land / water, high / low latitude)
4 types of air masses
mP – maritime polar (cool, wet)
mT – maritime tropical ( warm, wet)
cP – continental polar ( cold, dry)
cT – continental tropical ( hot, dry)
Fronts
Fronts – boundary between two air masses. Where two different air masses meet
4 types of fronts
1. Cold front - cold air takes place of warmer air
2. Warm front – warm air takes place of cooler air
3. Stationary front – not moving
4. Occluded front – when a two cold air massesforce a warm air mass to rise.
(strong wind and heavy rain)