Tonight February 8 Weather Review Weather map basics Energy that Drives the Storms (chapter 2) More Weather Maps (Isopleths) Classwork (HW#3) Homework #4

Weather Preview 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 Symbols and Maps

Station model 80 021 -23 63

Weather Symbols

Sky Symbols

Wind Symbols

Pressure Tendency

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 Total sky 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 76 953 +16 65 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 10 105 -4 8 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

Weather Maps

Weather Maps

Weather Maps

Weather Maps

Weather Maps

Weather Maps

Weather Maps

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

Slower and closer together ….. Faster and farther apart Cold Air vs. Warm Air Air temperature is a measure of the aver­age speed of the molecules. In the cold volume of air, the molecules move more slowly and crowd closer together. In the warm volume, they move faster and farther apart. 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 Heat energy absorbed and released. 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 The development of a thermal. A thermal is a rising bubble of air that carries heat energy upward by convection. Fig. 2.5, p. 40

Thermal Circulations The rising of hot air and the sinking of cool air sets up a convective circulation. Normally, the vertical part of the circula­tion is called convection, while the horizontal part is called wind. Near the surface the wind is advecting smoke from one region to another. 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 Radiation characterized according to wavelength. As the wavelength decreases, the energy carried per wave increases. 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 The sun’s electromagnetic spectrum and some of the descriptive names of each region. The numbers underneath the curve approximate the percent of energy the sun radiates in various regions. Mostly shorter wavelengths Fig. 2.8, p. 44

Electromagnetic Radiation SUN EARTH The hotter sun not only radi­ates more energy than that of the cooler earth (the area under the curve), but it also radiates the majority of its energy at much shorter wavelengths. (The area under the curves is equal to the total energy emitted, and the scales for the two curves differ by a factor of 100,000.) 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 Absorption of radiation by gases in the atmosphere. The shaded area represents the percent of radiation absorbed by each gas. The strongest absorbers of infrared radiation are water vapor and carbon dioxide. The bottom fi gure represents the percent of radiation absorbed by all of the atmospheric gases. Visit the Meteorology Resource Center to view this and other Active figures at www.cengage.com/login. Fig. 2.10, p. 46

A GREENHOUSE 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), ozone 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 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 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

Solar Radiation On the average, of all the solar energy that reaches the earth’s at­mosphere annually, about 30 per­cent (30/100) is reflected and scattered back to space, giving the earth and its atmosphere an albedo of 30 percent. Of the remaining solar energy, about 19 percent is absorbed by the atmosphere and clouds, and 51 percent is absorbed at the surface. Fig. 2.13, p. 50

ALBEDO Percent of sunlight reflected from clouds and earth surfaces Earth average albedo = 30% Surface Albedo (%) Earth and Atmosphere 30 Clouds (Thick) 60-90 Clouds (Thin) 30-50 Fresh Snow 75-95 Ice 30-40 Sand 15-45 Grassy Field 10-30 Plowed Field 5-20 Water 10 Moon 7

Atmospheric Energy Balance The earth-atmosphere energy balance. Numbers represent approximations based on surface observations and satellite data. While the actual value of each process may vary by several percent, it is the relative size of the numbers that is important. Fig. 2.14, p. 51

Global Energy Balance The average annual incoming solar radiation (yellow lines) absorbed by the earth and the atmosphere along with the average annual infrared radiation (red lines) emitted by the earth and the atmosphere. Fig. 2.15, p. 52

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.

Elliptical Orbit The elliptical path (highly exaggerated) of the earth about the sun brings the earth slightly closer to the sun in January than in July. Fig. 2.16, p. 52

Sun Angle Sunlight that strikes a surface at an angle is spread over a larger area than sunlight that strikes the surface directly. Oblique sun rays deliver less energy (are less in­tense) to a surface than direct sun rays. Visit the Meteorology Resource Center to view this and other active figures at www. cengage.com/login. Fig. 2.17, p. 53

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

Sun Angle During the Northern Hemi­sphere summer, sunlight that reaches the earth’s surface in far northern latitudes has passed through a thicker layer of absorbing, scattering, and reflecting at­mosphere than sunlight that reaches the earth’s surface farther south. Sunlight is lost through both the thickness of the pure at­mosphere and by impurities in the atmosphere. As the sun’s rays become more oblique, these effects become more pronounced. Fig. 2.20, p. 56

Sun and the Seasons As the earth revolves about the sun, it is tilted on its axis by an angle of 23½°. The earth’s axis always points to the same area in space (as viewed from a distant star). Thus, in June, when the Northern Hemisphere is tipped toward the sun, more direct sunlight and long hours of daylight cause warmer weather than in December, when the Northern Hemisphere is tipped away from the sun. Visit the meteorology Resource Center to view this and other active figures at www.cengage.com/login. Fig. 2.18, p. 53

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 N 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

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

Sun’s Seasonal Path Land of the Midnight Sun. A series of exposures of the sun taken before, during, and after midnight in northern Alaska during July. Fig. 2.19, p. 56

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

Contour Maps

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 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

Due next week (2/15/11) at the beginning of class. HOMEWORK #4 Due next week (2/15/11) at the beginning of class. Draw Isotherms at 10 degree intervals( i.e., 50, 60, 70, 80, 90 degrees).