1 / 27

Announcements

Announcements. Midterm exam #1 will be handed back at the end of class. Will go over written questions and give distribution of scores. Homework assignment #1 due next Monday. Groups 3A and 4A pick up labs on Monday.

sevita
Download Presentation

Announcements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Announcements Midterm exam #1 will be handed back at the end of class. Will go over written questions and give distribution of scores. Homework assignment #1 due next Monday. Groups 3A and 4A pick up labs on Monday. Athlete grade forms will be filled out today and turned in by me. Apologize for lateness on this, but needed to have exam grades for this.

  2. Summary of Force Balances:Why the wind blows

  3. NATS 101 Section 4: Lecture 17 Turbulence and Local Winds

  4. Couple of important loose ends from Chapter 8…

  5. Hydrostatic Balance:(One more) force balance in the vertical Mathematically: Solution to above equation: Vertical pressure gradient force + gravity = 0 An exponentially decaying solution of pressure with height

  6. Flashback:Change in density and pressure with height Density and pressure decrease exponentially with height. For each 16 km in altitude, the pressure decreases by a factor of 10. Explained by hydrostatic balance.

  7. Buys-Ballot’s Law If you stand with your back to the wind (in Northern Hemisphere): Low pressure on your left High pressure to your right. Crude approximation, assuming the winds are in geostrophic balance.

  8. Scales of Atmospheric Motion vs. Lifespan The general circulation Atmospheric oscillations We’ve already started to investigate some of the synoptic-scale features… Topics for today’s discussion Basically here’s our roadmap for the rest of the course.

  9. The smallest type of atmospheric motion is turbulence. Just a few bumps, folks! Nothing to be worried about! It’s what the airline pilot cheeringly calls “bumpy air” or “choppy air” on your flight. It seems like to me they never really seem to know exactly when it’s going to happen! Jay Jay the Happy Jet Plane Turbulence: Irregular atmospheric motion characterized by currents up and down, or eddies. A departure from smooth (or laminar) flow.

  10. Mechanical Turbulence (Forced Convection) Mechanical turbulence is ultimately due to changes in wind speed over a distance, or wind shear. The change can be due to (for example): Surface friction Obstructing objects or terrain features. Changes in wind speed above the ground.

  11. Billow CloudsA visual indicator of wind shear STRONG WINDS ABOVE CLOUD TURBULENT EDDIES WEAK WINDS BELOW CLOUDS

  12. Terrain-Induced Turbulence Where Jay Jay the Happy Jet Plane SHOULD NEVER FLY: In the vicinity of a mountain wave induced rotor!!

  13. Lenticular Cloud on Mt. Fuji:Indicative of mountain lee waves

  14. BOAC Flight 911: March 5, 1966Crashed on Mt. Fuji due to lee wave turbulence

  15. Thermal Turbulence(Free Convection) Formed by rising thermals due to surface heating during the day. These may form convective clouds by afternoon. So if you want the smoothest ride, take the morning flight!

  16. So Jay Jay the Happy Jet Plane decides to go from Tucson to Denver… Just a few bumps, folks! Nothing to be worried about! Why is he likely to have a bumpy ride?

  17. Percentage of positive reports of turbulence on U.S. commercial jet flights SUMMER WINTER COLORADO COLORADO (UCAR RAP) Mostly mechanical turbulence due to mountain waves Mostly thermal turbulence due to summer thunderstorms. COLORADO HAS THE MOST TURBULENT AIR AROUND!

  18. Flight Simulators Today’s pilots are well trained how to deal with turbulence, as well as other adverse weather phenomena, in sophisticated flight simulators. Modern jet aircraft also have instrumentation to indicate pilots of severe wind shear, largely through the efforts of research labs like National Center for Atmospheric Research.

  19. Local Winds:Sea-Land BreezeMountain-Valley Circulation Basically the same physical idea for each one: A direct thermal circulation which occurs a small enough scale that the pressure gradient is the dominant force which drives the wind. Driven by the diurnal cycle of solar heating.

  20. Sea-Land Breeze DAYTIME NIGHTIME PGF PGF Water is relatively cool Land is relatively warm Onshore flow at the surface Offshore flow aloft. Water is relatively warm Land is relatively cool Offshore flow at the surface Onshore flow aloft. Occurs because water has a high heat capacity, so it heats and cools more slowly than the land.

  21. Sea Breeze Circulation and Sea Breeze Front Sea breeze forces air to converge over land, leading to upward motion and formation of clouds and storms.

  22. Sea Breeze Front: North Carolina Example EARLY MORNING MID AFTERNOON LATE AFTERNOON MID MORNING (University of Wisconsin)

  23. Florida Peninsula Sea breeze is blowing the smoke from a forest file away from the Gulf of Mexico side (FL Dept. of Forestry).

  24. Mountain-Valley Winds NIGHTTIME DAYTIME Air is heated along mountain slopes Warmed air is locally less dense than the surrounding air above the valley. Upslope flow. Air is cooled along mountain slopes Cooled air is locally more dense than the surrounding air above the valley. Downslope flow.

  25. Local Topography of Tucson, AZ CATALINA MTNS. We’re surrounded by mountains on three sides, so mountain valley circulations play a BIG role in our weather—especially during the monsoon! TUCSON MTNS. X University of AZ RINCON MTNS.

  26. Summary of Lecture 17 Hydrostatic balance is the force balance in the vertical. Gravity balances the upward pressure gradient force. This explains the exponential decrease in pressure with height. Buy’s ballot law gives a crude approximation to where high and low pressure are relative to your position. Various scales of atmospheric motion are used to classify weather and climate phenomena. Be familiar with them. Turbulence is irregular atmospheric motion characterized by eddies. Mechanical: Due to wind shear Thermal: Due to differential heating leading to thermals. The local circulations mentioned today are direct thermal circulations driven by the diurnal cycle of solar heating. Sea-land breezes: Occur because of the difference in heat capacity between water and land. Mountain- valley winds: Occur because of the heating and cooling of elevated terrain. Important for weather in the western U.S., especially in summer.

  27. Reading Assignment and Review Questions Reading: Remainder of Ch. 9 Chapter 9 Questions Questions for Review (8th ed.): 1,3,4,5,6,8,20,21 (9th ed.): 1,3,4,5,6,7,9,21,22 Questions for Thought: 1,5,8,10,11

More Related