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February 8 Weather Review Weather map basics Energy that Drives the Storms (chapter 2) More Weather Maps ( Isopleths ) Classwork (HW#3) Homework #4. Tonight. What is the forecast for next week? Monday? Tuesday? Wednesday?
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February 8 • Weather Review • Weather map basics • Energy that Drives the Storms (chapter 2) • More Weather Maps (Isopleths) • Classwork (HW#3) • Homework #4 Tonight
What is the forecast for next week? • Monday? • Tuesday? • Wednesday? • During the course of the week try and keep track if the forecast • Changes? • Is accurate? Weather Preview
Station model 80 021 -23 63
Station model 80 021 -23 63
Station model 80 021 -23 63 Temperature Surface: ºF Upper air: ºC
Station model 80 021 -23 63 Dew point temperature Surface: ºF Upper air: ºC
Station model 80 021 -23 63 Totalsky cover ** Depicted by shading in circle
Station model 80 021 -23 63 Current weather conditions ** If blank, “no weather”
Station model 80 021 -23 63 Wind direction – of wind toward center
Station model 80 021 -23 63 Wind speed Long barb = 10 knots Short barb = 5 knots Flag = 50 knots ** Notice range of wind speeds (i.e., 28-32 knots)
Station model 80 021 -23 63 Sea level pressure **If first number is 5 or greater, then place 9 in front --Otherwise, place 10 in front **Place decimal point between last two numbers
Station model 80 021 -23 63 Change in surface pressure during last 3 hours ** In tenths of mb ** Line describes how pressure changes over time from left to right
Example 1 • Temperature: 76 ºF • Dew point: 65 ºF • Sky cover: Completely overcast • Current weather: Light rain • Wind direction and speed: Southwest at 15 knots • Sea level pressure: 995.3 mb • Pressure tendency: Increase of 1.6 mb; rising steadily 76 953 +16 65
Example 2 • Temperature: 10ºF • Dew point: 8ºF • Sky cover: 7/10 or 8/10 • Current weather: Snow shower • Wind direction and speed: North at 3-7 knots • Sea level pressure: 1010.5 mb • Pressure tendency: Decrease of 0.4 mb; falling, then steady 10 105 -4 8
High & Low Pressure Systems • Air pressure Patterns are main organizing feature • Circulation in Northern Hemisphere • Clockwise around Highs (H) • CCW around Lows (L) • Clouds & Precip around Lows • Temperature patterns result from latitude, wind flow and cloud cover
Plotting Fronts • Boundary between Different Air Masses • Types of Fronts
CHAPTER 2 ENERGY THAT DRIVES THE STORMS
ENERGY AND HEAT TRANSFER • Energy is the capacity to do work on some form of matter • Potential energy: The total amount of energy stored in any object is capable of doing • Kinetic energy: Any moving substance possesses energy of motion
Cold Air vs. Warm Air Slower and closer together ….. Faster and farther apart Fig. 2.1, p. 37
ENERGY AND HEAT TRANSFER • Atoms and molecules have kinetic energy due to their motion (heat energy) • Sun’s radiant energy most important • Air temperature is a measure of the average kinetic energy of its molecules
ENERGY AND HEAT TRANSFER • Heat = energy transferred because of a temperature difference • After heat is transferred, it is stored as internal energy • Heat is transferred in the atmosphere by • Conduction • Convection • Radiation
ENERGY AND HEAT TRANSFER • Latent heat: energy required to change a substance, such as water, from one state to another • Evaporation = cooling process, absorption of latent heat from the environment • Condensation = warming process, release of latent heat to the environment
Changes of State Fig. 2.2, p. 37
ENERGY AND HEAT TRANSFER • Conduction: the transfer of heat from molecule to molecule • Always flows from warmer to colder • Air is an extremely poor conductor of heat
ENERGY AND HEAT TRANSFER • Convection = heat transfer by the mass movement of a fluid (water or air) • Example: Pan of boiling water • Convection circulation: warm air expands and rises then cools and sinks • Thermal cell, convection, thermals
Thermal Circulations Fig. 2.5, p. 40
Thermal Circulations Fig. 2.6, p. 40
ENERGY AND HEAT TRANSFER • Radiation = Energy transfer via electromagnetic waves • Radiation and Temperature • Hotter objects • Emit shorter wavelengths • Emit radiation at a greater rate or intensity
Electromagnetic Radiation Fig. 2.7, p. 41
ENERGY BALANCING ACT • Radiation of the Sun and Earth • Sun (6000 K) emits mostly shortwave radiation • Earth emits mostly longwave radiation
SUN’S ELECTROMAGNETIC SPRECTRUM Mostly shorter wavelengths Fig. 2.8, p. 44
ElectromagneticRadiation SUN EARTH Fig. 2.9, p. 44
ENERGY BALANCING ACT • Selective Absorbers: • Good absorbers are good emitters at a particular wavelength, and vice versa. • Greenhouse effect: the atmosphere selectively absorbs infrared radiation from the Earth’s surface but acts as a window and transmits shortwave radiation
Atmospheric Absorption of Radiation Fig. 2.10, p. 46
A GREENHOUSE • Glass is transparent to short visible wavelengths (SW) but opaque to long infrared (LW) wavelengths.