UW ATMS 101 - Weather and Climate

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Lecture 2Weather and ClimateWeather: The condition of the atmosphere at any particular time and place.Weather ElementsClimate: Average weather and the range of weather over many years. Can include:MeteorologyThe study of the atmosphereFrom Aristotle, Meteorologica (340 BC)Modern terms:1500’s: thermometer1600’s: barometer1700’s: hygrometer1800’s: ocean commerce Æ mariners logs1840’s: telegraph Æ weather maps1910’s: Norwegian school: front, airmass1940’s: aviation Æ weather balloons Æ 3D1950’s: computers, weather radar1960’s: weather satellites3000’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, atmo...Weather From Below: Surface Weather Map• Combines compact representation of several weather elements to visualize surface patterns of te...Weather’s Vertical Profile: The Radiosonde• Weather balloons, called radiosondes, are used to sample the vertical structure of the atmosphe...• They measure TemperatureHumidityPressureand are tracked to determine winds.• Since the 1950s, radiosondes are launched at 00 and 12 GMT every day at a global network of sit...• This network has enormous gaps over the oceans, and is sparse to nonexistent in less affluent n...The North American Radiosonde Network• Stations 300-500 km apart• Nearest stations:UIL: Quillayute, WA(on Pacific coast)OTX: Spokane, WAYZT: Pt Hardy , BC(N tip Vancouver Island)SLE: Salem, OR(Oregon coast)A Radiosonde Sounding(Quillayute, WA, 1200 GMT 6 Jan 1998)• Tilted blue lines mark constant temperature. Temperature decreases with height in troposphere u...• Wind vane indicates direction, barbs indicate wind speed - filled triangle = 50 knots (55 mph)full line = 10 ktshalf line = 5 ktsTemperature and HeatMicroscopic 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 differ...Temperature ScalesGabriel Fahrenheit (1714): 0°F= lowest freezingpoint of brine,100°F = body temperatureAnders Celsius (1736): 0°C = freezing point, 100°C = boiling pointof water.Lord Kelvin (1800s): Temperature scale based on absolute zero:°K = °C + 273.Heat CapacityThe amount of heat required to raise the temperature of an object 1 C is its heat capacityWhy is beach sand hot on a tropical summer day while water is comfortable?This is also why land warms up and cools down faster and more than lakes or oceans as the seasons...Lecture 2Weather and ClimateWeather: The condition of the atmosphere at any particular time and place.Weather Elements1.Air temperature 5. Precipitation2.Air pressure 6. Visibility3.Humidity 7. Winds4.CloudsClimate: Average weather and the range of weather over many years. Caninclude: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 Jan1 in Seattle)MeteorologyThe study of the atmosphereFrom 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: thermometer1600’s: barometer1700’s: hygrometer1800’s: ocean commerce → mariners logs1840’s: telegraph → weather maps1910’s: Norwegian school: front, airmass1940’s: aviation → weather balloons → 3D1950’s: computers, weather radar1960’s: weather satellites3000’s: we believe the weather forecast!Weather From Above - Satellite View• In visible light, see cloud pat-terns.• Looking in other cleverly cho-sen wavelengths, can deducecloud-top temperature, moist-ness, atmospheric temperatureprofile, sea-surface winds, etc.EOM1.10Weather From Below: Surface Weather Map• Combines compact representation of several weather elements to visualizesurface patterns of temperature, air motion, storms, and precipitation.EOM 1.12Weather’s Vertical Profile: The Radiosonde• Weather balloons, called radiosondes, are used tosample the vertical structure of the atmosphere upto about 30 km.• They measure TemperatureHumidityPressureand are tracked to determine winds.• Since the 1950s, radiosondes are launched at 00and 12 GMT every day at a global network ofsites for weather forecasting.• This network has enormous gaps over the oceans,and is sparse to nonexistent in less affluentnations.EOM, p 11The North American Radiosonde Network• Stations 300-500 kmapart• Nearest stations:UIL: Quillayute, WA (on Pacific coast)OTX: Spokane, WAYZT: Pt Hardy , BC(N tip Vancouver Island)SLE: Salem, OR (Oregon coast)A Radiosonde Sounding(Quillayute, WA, 1200 GMT 6 Jan 1998)• Tilted blue lines markconstant temperature.Temperature decreaseswith height in tropo-sphere up to tropo-pause, nearly constantin stratosphere• Wind vane indicatesdirection, barbs indi-cate wind speed -filled triangle = 50knots (55 mph)full line = 10 ktshalf line = 5 ktsTemperatureDew pointTropopauseStratosphereTroposphereTTemperatureHeight80 kt wind from westTemperature and HeatMicroscopic 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 theirtemperature difference.Temperature ScalesGabriel Fahrenheit (1714):0°F= lowest freezing point of brine,100°F = body temperatureAnders Celsius (1736):0°C = freezing point,100°C = boiling point of water.Lord Kelvin (1800s): Tem-perature scale based onabsolute zero: °K = °C + 273.EOM21Heat CapacityThe amount of heat required to raise the temperature of an object 1 C is itsheat capacity• Proportional to the mass of object• Depends somewhat on the composition. (liquid water has a ‘specific’ heatcapacity (per unit mass) 4-5 times that of sand, rock, or air.Why is beach sand hot on a tropical summer day while water iscomfortable?• The same energy from sunlight is absorbed in a very shallowlayer of sand (a few cm), but a deep layer of water (50 m), sothe sand heats up much faster.This is also why land warms up and cools down faster and morethan lakes or oceans as the seasons or time of day


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UW ATMS 101 - Weather and Climate

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