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Week 13 Notes

TONIGHT Midterm #2 Corrections (HW#11) Thunderstorms and Tornadoes (Chp 10) Homework #12 – “Perfect Climate” Next Week (Apr 28) Hurricanes (Chp 11) Air Pollution (chp 12) Climate Classifications May 5 Climate Change TERM PAPERS DUE May 12 FINAL EXAM Extra Credit Papers Due.

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Week 13 Notes

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  1. TONIGHT • Midterm #2 Corrections (HW#11) • Thunderstorms and Tornadoes (Chp 10) • Homework #12 – “Perfect Climate” • Next Week (Apr 28) • Hurricanes (Chp 11) • Air Pollution (chp 12) • Climate Classifications • May 5 • Climate Change • TERM PAPERS DUE • May 12 • FINAL EXAM • Extra Credit Papers Due Week 13 Notes

  2. Midterm #2 • Class Average = 71 points • Scores adjusted by +4 points • pre-Midterm Review • w/ review: 77% • wo/ review: 61% • Changing answers • About 2/3 of changed answers were wrong

  3. Homework #11 • Same as before • TYPED (no exceptions) • Correct Your Missed Questions • Must be 3 part answer • Correct answer • 1 paragraph (2 or 3 sentences) explaining the correct answer • Source of correct answer • DUE AT BEGINNING OF CLASS NEXT WEEK (Apr 28) • Well-done complete corrections = 10 points • Points deducted for incomplete or not following directions Midterm #2 Corrections

  4. Example Correction Example: # 39. C, Scattering • The sky is blue because of Rayleigh scattering. The size of oxygen and nitrogen molecules selectively scatter the shorter blue wavelengths. It is this prominent scattered blue light that our eyes see. • Ahrens text: pg 405 (or Atmospheric Optics PowerPoint, slide # 62)

  5. 6-10 Pages, typed, double-spaced (exclusive of figures, bibliography) • Scientific Style – • ABSOLUTELY NO 1ST PERSON.  This is a science paper. • Well-organized • Properly documented • At least 4 CREDIBLE reference sources (only half may be Internet only source).  • ABSOLUTELY NO WIKIPEDIA.COM • References Format: APA http://www.wisc.edu/writetest/Handbook/DocAPA.html • Grading: Maximum 200 points • Content, Accuracy - 150 points • Organization, Format - 30 points • Grammar, Style - 20 points Term Papers(and Extra Credit Term Papers)

  6. Thunderstorms and Tornadoes

  7. Thunderstorms • Not Rare • 40,000 Times Each Day Overthe World • Frequency Is Different but Every Place in the World has T-storms • T-storm Hazards • Lightning • Flash Floods • Hail • Winds (Downbursts, Microbursts) • Tornadoes • Hurricanes

  8. Thunderstorm Formation • Warm Humid Rises into an Unstable Atmosphere • Trigger needed to Start Lift • Unequal heating • Frontal Lift • Terrain • Enhanced by Strong Diverging Winds Aloft • Cumulonimbus • Types • Ordinary (Air Mass) Thunderstorms • Severe Thunderstorms

  9. Air Mass Thunderstorms • Most Common • Least Destructive • Limited Life of Less Than an Hour • Localized • Life Cycle • Cumulus Stage • Mature Stage • Dissipative Stage

  10. Cumulus Stage • Unstable Air Rises by Localized Convection • Vertical Motion 10 to 45 mph • Cloud Extends Above Freezing Level • Ice Crystals Form and Grow by Bergeron Process • Precipitation Begins to Fall

  11. Mature Stage • Heavy Rain Drags Air forming Downdrafts • Downdrafts Strengthened By Cooling From Evaporation • Most Vigorous Rain along edges of cloud • Updrafts Dominate Inner Part of Cloud

  12. Mature Thunderstorm

  13. Dissipating Stage • As Precipitation and downdrafts dominate then updrafts cut off • Only 20% of Moisture Falls as Rain – the Rest Evaporates

  14. Severe Thunderstorms • Defined as • Wind Speeds Exceed 58 mph • Hailstones Greater Than ¾” diameter • Can Spawn Tornadoes • Extreme Downdrafts and Updrafts Intensify Storm • Scale: 6 to 60 mi Across Mesoscale

  15. Severe Thunderstorms • Large Area Allows Several Storms to Cluster (Multi Cell Storms) • Mesoscale Convective Systems (MCSs) • Oval Clusters Are Mesoscale Convective Complexes (MCCs) • Linear Bands Are Squall Lines • SupercellsContain a Single Updraft Zone • Appear in Isolation or as Part of MCCs • Individual ButStorms Develop From A Common Origin

  16. Mesoscale Convective Systems (MCSs) • Cover Large Parts of States • Life Span: up to 12 Hours or more • Accounts for 60% of All Rain in Middle of US and Canada • Surrounding Air and Inflow Supports Stronger Winds and Heavier Precipitation

  17. Mesoscale Convective Systems (MCSs)

  18. Mesoscale Convective Complexes (MCCs) • Oval or Roughly Circular • Organized Systems Containing Numerous ralTstorms • Not All Produce Severe Storms But They Are Self-Propagating • Create Downdrafts That Produce Other Cells • Consider Large Cluster of Thunderstorms • Warm Humid Air at Surface (mT, Wind S) • Dry Air Above (CT, Mexico, Wind SW) • Wind Shear • Downdraft From Other Storms • Outflow Boundary

  19. Mesoscale Convective Complexes (MCCs)

  20. Squall Lines • Large Number of Individual Storm Cells • Linear Band ~ 300 mi in Length • Form 60 to 180 mi ahead of Cold Front

  21. Squall Lines

  22. Gusts Fronts

  23. Gusts Front

  24. Supercell Thunderstorms

  25. Supercell Thunderstorms

  26. Supercell Thunderstorms • Diameter 12 to 30 mi • Smaller than Squall Line or MCCs • Most Violent • Life Span: • 2 to 4 Hours

  27. Supercell Structure

  28. Thunderstorm Moisture

  29. Thunderstorm Distribution Avg. Number of Thunderstorm Days per year

  30. Lightning Formation • Excess negative and excess positive charges • Lightning: attempt to equalize electrical differences • Air is a poor conductor, thus electrical potential (charge differences) must be very high before lightning will occur

  31. Lightning Formation • Stepped leader: advancing, branching shaft of negative charges • As stepped leader approaches ground, a spark of positive charges surges upward from the ground • Stepped leader and upward surge create a path for current flow

  32. Lightning Formation • Negative current flows downward from cloud

  33. Lightning Formation • Return stroke: positive current flow upward • Lightning is a sequence of strokes and return strokes • • Usually 2-3 strokes; sometimes up to 20 strokes

  34. Lightning Causes • Most Common Theory • Collusion of Hail stone and Ice Crystal • Ice Crystal is Positive Charged – Colder Lighter - Carried to Top of Cloud • Hailstone - Negative Charged - Heavier Stays More in Bottom of Cloud

  35. Types of Lightning Cloud-to-Air Within Cloud Cloud-to-Cloud Cloud-to-Ground

  36. Cloud-to-Ground Lightning

  37. Cloud-to-Ground Lightning

  38. Cloud-to-Ground Lightning

  39. Thunder • Air in Column is Heated to 50,000° F • Heated Air Expands Explosively • Shockwave heard as a Loud Noise • Speed Difference Flash and Sound • Sounds Travels at 1100 feet per second • Light Travels at 186,000 miles per second • Each 5 seconds between flash and sound is a mile. • Nearby Thunder Is Sharp • Distant Thunder Echoes and “Rumbles”

  40. Types of Lightning • Cloud-to-Cloud • 80% of All Lightning • Sheet Lightning • Flash is Obscured by Clouds • Sky Lights Up Uniformly • Cloud-to-Ground (Water) • 20% • Negative Charges at Base of Cloud

  41. Other Lightning Types • Ball Lightning • Appears as a Round, Glowing Mass, Basketball Size • One Form Avoids Electric Conductors and Another is Attracted • Saint Elmo’s Fire • Ionization of Air Just Before Cloud-to-ground Strike • Causes Church Steeples and Ship’s Mast to Glow Green-blue, Giving Out Sparks That Hiss

  42. Other Lightning Types

  43. Lightning Statistics • 12,000 fires/yr in US are started by lightning • 5.2 million acres • $50 million worth of timber destroyed • Total Lightning Losses/ Year: $5 billion • Deaths: • Avg =62/year • 2008 • 27 killed • 302 injured

  44. Lightning • Electrical Charge Builds in Air Before Lightning Strikes • If Nothing Else Can be Done Flatten Out on Ground Get Away From High Points (Trees)

  45. Lightning Safety • Lightning can strike up to 15 miles from where it’s raining • Take cover in a building • Stay away from electrical appliances • Get Out of the Water • Stay in the Car Unless It Is a Convertible

  46. Downbursts • Downbursts • Strong Downdrafts up to 165 mph • Spread in All Directions to Form Intense Horizontal Winds • Damage Sometimes Mistaken for Tornado • Microburst • Downburst Less Than 4 km (2.5 mi) in Diameter • Airport Danger due to Strong Wind Shear • Headwind for Lift Followed by Tailwind Causing Negative Lift

  47. Downbursts

  48. Worst Tornado Movies • Twister • Revenge of the Twisters • Category 7 • Any other movie with a tornado in it … Except • The Wizard of Oz

  49. Tornadoes • Extremely Rapid, Rotating Winds Beneath the Base of Cumulonimbus Clouds • Most Rotate Cyclonically (CCW NH) • Shapes • Some Very Thin rope-shaped Columns • Others Characteristic Funnel Shape Smallest at Surface • Result From an Extraordinarily Large Pressure Difference Over a Few Tenths of a mile (100 mb)

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