Lecture 2 Weather and Climate Weather The condition of the atmosphere at any particular time and place Weather Elements 1 Air temperature 5 Precipitation 2 Air pressure 6 Visibility 3 Humidity 7 Winds 4 Clouds Climate Average weather and the range of weather over many years Can include The whole year mean annual rainfall in Seattle 1950 present A season e g Dec Jan Feb winter Jun Jul Aug summer A month e g mean January snowfall in Seattle One particular day of the year Average and record high low temps for Jan 1 in Seattle Meteorology The study of the atmosphere From Aristotle Meteorologica 340 BC Meteors objects seen in air and falling from the sky Modern terms Meteoroids extraterrestrial Hydrometeors falling water and ice particles 1500 s thermometer 1600 s barometer 1700 s hygrometer 1800 s ocean commerce mariners logs 1840 s telegraph weather maps 1910 s Norwegian school front airmass 1940 s aviation weather balloons 3D 1950 s computers weather radar 1960 s weather satellites 3000 s we believe the weather forecast Weather From Above Satellite View In visible light see cloud patterns Looking in other cleverly chosen wavelengths can deduce cloud top temperature moistness atmospheric temperature profile sea surface winds etc EOM1 10 Weather From Below Surface Weather Map EOM 1 12 Combines compact representation of several weather elements to visualize surface patterns of temperature air motion storms and precipitation Weather s Vertical Profile The Radiosonde Weather balloons called radiosondes are used to sample the vertical structure of the atmosphere up to about 30 km They measure Temperature Humidity Pressure and are tracked to determine winds Since the 1950s radiosondes are launched at 00 and 12 GMT every day at a global network of sites for weather forecasting This network has enormous gaps over the oceans and is sparse to nonexistent in less affluent nations EOM p 11 The North American Radiosonde Network Stations 300 500 km apart Nearest stations UIL Quillayute WA on Pacific coast OTX Spokane WA YZT Pt Hardy BC N tip Vancouver Island SLE Salem OR Oregon coast A Radiosonde Sounding Height Quillayute WA 1200 GMT 6 Jan 1998 Tilted blue lines mark constant temperature Temperature decreases Stratosphere with height in troposphere up to tropoTropopause pause nearly constant Temperature in stratosphere Troposphere Wind vane indicates 80 kt wind direction barbs indifrom west cate wind speed filled triangle 50 Dew point knots 55 mph full line 10 kts Temperature half line 5 kts Temperature and Heat Microscopic View of Temperature Energy of Random Jiggling related to average molecule velocity 500 m s 1 at room temperature Heat Energy being transferred from one object to another as a result of their temperature difference Temperature Scales Gabriel Fahrenheit 1714 0 F lowest freezing point of brine 100 F body temperature Anders Celsius 1736 0 C freezing point 100 C boiling point of water Lord Kelvin 1800s Temperature scale based on absolute zero K C 273 EOM 2 1 Heat Capacity The amount of heat required to raise the temperature of an object 1 C is its heat capacity Proportional to the mass of object Depends somewhat on the composition liquid water has a specific heat capacity per unit mass 4 5 times that of sand rock or air Why is beach sand hot on a tropical summer day while water is comfortable The same energy from sunlight is absorbed in a very shallow layer of sand a few cm but a deep layer of water 50 m so the sand heats up much faster This is also why land warms up and cools down faster and more than lakes or oceans as the seasons or time of day changes
View Full Document
Unlocking...