Tonight Sept 7 Weather Review Weather Review Weather map basics Weather map basics Energy that Drives the Storms (chapter 2) Energy that Drives the Storms (chapter 2) More Weather Maps (Isopleths) More Weather Maps (Isopleths) Classwork (HW#3) Classwork (HW#3) Homework #4 Homework #4

Weather Review Hrcn Earl Visible

Weather Review Hrcn Earl Infrared (IR)

Weather Review Hrcn Earl Enhanced IR

Weather Review Hrcn Earl Visible

Weather Review “ Hurricane Force Wind Gusts ” Criteria: 1-minute sustained winds ≥ 74 mph P eak 3 to 5-second gusts ~ 30% higher Exerted Force: proportional to the square of the wind speed Force from a 74 mph gust = 14.0 psf Force from a 96 mph gust = 23.6 psf 69% higher.

Weather Review TS Hermine Visible

Weather Review TS Hermine Infrared

Weather Review TS Hermine Enhance Infrared

Weather Review TS Hermine Radar

Weather Review TS Hermine QPF

Weather Symbols and Maps

Station model

Weather Symbols

Sky Symbols

Wind Symbols

Pressure Tendency

Station model

Temperature Surface: ºF Upper air: ºC

Station model Dew point temperature Surface: ºF Upper air: ºC

Station model Total sky cover ** Depicted by shading in circle

Station model Current weather conditions ** If blank, “no weather”

Station model Wind direction – of wind toward center

Station model Wind speed Long barb = 10 knots Short barb = 5 knots Flag = 50 knots ** Notice range of wind speeds (i.e., knots)

Station model Sea level pressure **If first number is 5 or greater, then place 9 in front --Otherwise, place 10 in front --Otherwise, place 10 in front **Place decimal point between last two numbers

Station model 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 Temperature: 76 ºF Dew point: 65 ºF Dew point: 65 ºF Sky cover: Completely overcast Sky cover: Completely overcast Current weather: Light rain Current weather: Light rain Wind direction and speed: Southwest at 15 knots Wind direction and speed: Southwest at 15 knots Sea level pressure: mb Sea level pressure: mb Pressure tendency: Increase of 1.6 mb; rising steadily Pressure tendency: Increase of 1.6 mb; rising steadily

Example Temperature: 10ºFTemperature: 10ºF Dew point: 8ºFDew point: 8ºF Sky cover: 7/10 or 8/10Sky cover: 7/10 or 8/10 Current weather: Snow showerCurrent weather: Snow shower Wind direction and speed: North at 3-7 knotsWind direction and speed: North at 3-7 knots Sea level pressure: mbSea level pressure: mb Pressure tendency: Decrease of 0.4 mb; falling, then steadyPressure tendency: Decrease of 0.4 mb; falling, then steady

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

Weather Maps

CHAPTER 2 ENERGY THAT DRIVES THE STORMS 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

Fig. 2.1, p. 37 Cold Air vs. Warm Air Slower and closer together ….. Faster and farther apart

ENERGY AND HEAT TRANSFER Atoms and molecules have kinetic energy due to their motion (heat energy) Most important energy in terms of weather and climate is radiant energy from the sun Air temperature is a measure of the average kinetic energy of its molecules

ENERGY AND HEAT TRANSFER Heat is energy being transferred from one object to another 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 is a cooling process due to absorption of latent heat from the environment Condensation is a warming process due to a release of latent heat to the environment

Fig. 2.2, p. 37 Changes of State

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: transfer of heat 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

Fig. 2.5, p. 40 Thermal Circulations

Fig. 2.6, p. 40 Thermal Circulations

ENERGY AND HEAT TRANSFER Radiation: Energy in the form of electromagnetic waves Radiation and Temperature – Hotter objects Emit shorter wavelengths Emit radiation at a greater rate or intensity

Fig. 2.7, p. 41 Electromagnetic Radiation

ENERGY BALANCING ACT Radiation of the Sun and Earth – Sun (6000 K) emits mostly shortwave radiation – Earth emits mostly longwave radiation

Fig. 2.8, p. 44 SUN’S ELECTROMAGNETIC SPRECTRUM Mostly shorter wavelengths

Fig. 2.9, p. 44 SUN EARTH Electromagnetic Radiation

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

Fig. 2.10, p. 46 Atmospheric Absorption of Radiation

A GREENHOUSE Glass is transparent to short visible wavelengths (SW) but opaque to long infrared (LW) wavelengths. Glass is transparent to short visible wavelengths (SW) but opaque to long infrared (LW) wavelengths.

w/o GREENHOUSE GASES

w/ GREENHOUSE GASES

ENERGY BALANCING ACT Greenhouse Enhancement – Global warming is occurring due to an increase in greenhouse gases Carbon dioxide, methane, nitrogen oxide, chloroflourocarbons (CFCs) – Positive feedbacks continue the warming trend. – Negative feedbacks decrease warming.

Positive Feedback When the response in a second variable reinforces the change in the initial variable When the response in a second variable reinforces the change in the initial variable Example of positive feedback: Example of positive feedback: – Global temperatures increase – Increase in temperature melts the ice and snow in the upper latitudes – Loss of ice and snow results in a lower albedo at the surface in the upper latitudes – Lower albedo leads to less reflection and more insolation – More insolation results in warmer temperatures

Negative Feedback When the response in a second variable lessens the change caused by the initial variable When the response in a second variable lessens the change caused by the initial variable Example of negative feedback: Example of negative feedback: – Global warming leads to more atmospheric water vapor – Increased water vapor leads to increased cloud cover – Increased cloud cover leads to a higher albedo – Higher albedo results in less insolation at the surface – Reduced insolation at the surface leads to cooling

Fig. 2.13, p. 50 Solar Radiation

ALBEDO Percent of sunlight reflected from clouds and earth surfacesPercent of sunlight reflected from clouds and earth surfaces Earth average albedo = 30%Earth average albedo = 30% Surface Albedo (%) Earth and Atmosphere30 Clouds (Thick)60-90 Clouds (Thin)30-50 Fresh Snow75-95 Ice30-40 Sand15-45 Grassy Field10-30 Plowed Field5-20 Water10 Moon7

Fig. 2.14, p. 51 Atmospheric Energy Balance

ENERGY BALANCING ACT Annual Energy Balance – 50% of insolation reaches the earth’s surface – Earth absorbs 147 units, radiates 117 units 30 unit surplus, warm – Atmosphere absorbs 130 units, radiates 160 units 30 unit deficit, cool – Tropics have a surplus of energy

Fig. 2.15, p. 52 Global Energy Balance

ENERGY BALANCE

WHY THE EARTH HAS SEASONS Earth revolves in elliptical path around sun every 365 days. Earth rotates counterclockwise or eastward every 24 hours. Earth closest to sun (147 million km) in January, farthest from sun (152 million km) in July. Distance not the only factor impacting seasons.

Fig. 2.16, p. 52 Elliptical Orbit

Fig. 2.17, p. 53 Sun Angle

WHY THE EARTH HAS SEASONS Energy reaching the earth’s surface, result of: – Distance from the sun – Solar angle – Length of daylight. Earth tilted toward the sun: – Higher solar angles and longer days

Fig. 2.20, p. 56 Sun Angle

Fig. 2.18, p. 53 Sun and the Seasons

WHY THE EARTH HAS SEASONS Seasons in the Northern Hemisphere – Summer solstice: ~ June 21 Sun directly above Tropic of Cancer (23.5° N) Longer days in N Hemisphere – Winter solstice: ~ December 21 Sun directly above Tropic of Capricorn (23.5° S) Shorter days in S Hemisphere – Autumnal and Vernal Equinox: ~ Sep 22, Mar 20 Sun directly above Equator All locations have a 12 hour day

Table 2.3, p. 57

Stepped Art Fig. 2.22, p. 58 Sun’s Seasonal Path

Fig. 2.19, p. 56 Sun’s Seasonal Path

WHY THE EARTH HAS SEASONS Seasons in the Southern Hemisphere – Opposite timing of N Hemisphere – Closer to sun in summer but not significant difference

ISOPLETHS

Contour Maps

ISOBARS

ISOTHERMS

ISOTACHS

ISOHYET

ISOPLETHS °Connects all points that have the same value °Iso = equal (Greek) °Also called “Isolines” °Types °Isobar = pressure °Isallobar = pressure change per time °Isotherm = temperature °Isohyet = rainfall °Isonif = snowfall °Isoryme = frost incidence °isoneph = cloudiness °isotach = wind speed

ISOPLETHS (cont’d) °Rules °Only through exact value of isopleth °Higher side and lower side °All higher should be on the same side of the line °Draw for all values °Spacing by interpolation °Spacing indicates rate of change (I.e., gradient) °Isopleths form closed loops °Isopleth never cross one another

ISOPLETHS (cont’d) DRAWING HINTS DRAWING HINTS – Note location of lowest and highest values – Begin around these low or high values and gradually work outward – Sketch lightly to get spacing and orientation of – Smooth the isopleths. Isopleths generally do not have sharp bends

ISOPLETHS Draw 6.5 contour

ISOPLETHS

ISOPLETHS Draw even contours

ISOPLETHS

ISOTHERMS Draw 10, 20, 30,40, 50, 60, 70 degree contours

ISOTHERMS

Isodrosotherms

Isodrosotherms

HOMEWORK #4 Draw Isotherms at 10 degree intervals( i.e., 50, 60, 70, 80, 90 degrees). Due next week (9/14/09) at the beginning of class.