1. NATS 101 Lecture 18 Local Winds

2. Supplemental References for Today’s Lecture
Danielson, E. W., J. Levin and E. Abrams, 1998: Meteorology. 462 pp. McGraw-Hill. (ISBN )

3. Review: Forces for Curved Flow
Assume PGF constant size along entire channel
PGF
5700 m
5640 m
Wind
PGF
Geo Wind
PGF CF CF
Ridge
Wind
Centripetal = CF + PGF
Centripetal << CF or PGF
Gradient Wind Balance CF
Trough

4. Super-geostrophic
Sub-geostrophic

5. Divergence and Convergence
Ridge
Divergence Mass Loss
Convergence Mass Gain
Trough
Large
Mass transport in channel
Small

6. Divergence Convergence

7. Convergence Divergence

8. Vertical Motion Ridge Ridge Trough
Gedzelman, p249
Mass Conservation leads to Upward motion beneath regions of divergence Downward motion beneath regions of convergence

9. Review: Friction Pressure Gradient Force 1004 mb Friction Wind 1008 mb
Coriolis Force
Because PGF becomes larger than CF, air parcel will turn toward lower pressure.
Friction Turns Wind Toward Lower Pressure.
Eventually, a balance among the PGF, Coriolis and Frictional Force is achieved.

10. Flow at Surface Lows and Highs
Gedzelman, p249
Spirals Outward
Divergence
Spirals Inward
Convergence

12. Friction Induced Vertical Motion
downward motion
upward motion
Ahrens, Fig 6.21

13. Atmospheric Scales of Motion
Ahrens, Fig 7.1

14. Review: Thermally Direct Circulation
Heat
Warm
Cold
Rising
Sinking
DIV
CON

15. Sea Breeze Development (Courtesy of Mohan Ramamurthy, WW2010)3 4

16. Sea Breeze Development (Courtesy of Mohan Ramamurthy, WW2010)5 6
Rising
Sinking
DIV
CON
Heat 7

17. Sea Breeze versus Land Breeze (Courtesy of Mohan Ramamurthy, WW2010)PM
Stronger Temperature contrast during PM than during AM
Sea breezes are stronger than land breezes AM
LAX Airport
4 PM upper
7 AM lower

18. Florida Satellite Loop
Sea Breeze
Regular feature of many coastal areas
California, Florida, Gulf Coast
Occurs along large lakes-Great Lakes
Typically strongest during Spring-Summer
Can penetrate inland 50 km or more
Temperatures can drop ~10oC
Nose of cool air can trigger thunderstorms
Florida Satellite Loop

19. Mountain-Valley Breeze
Rising
Sinking
DIV
CON
Heat
Sun warms slopes Density decreases Air rises
IR cools slopes Density increases Air drains
Ahrens, Older Ed.
Mountain-Valley circulation important to Tucson
Convection over Catalinas during PM summer.
SE drainage flows during early AM all year.

20. Phoenix-Tucson Diurnal WindsAM
TUS
Phoenix-Tucson Diurnal Winds PM
TUS
5 PM
5 AM
PM heating
AM cooling
5 PM
5 AM
PM heating
AM cooling AM
PHX PM
PHX

21. Darwin was Right
The Darwin "Natural Selection" Awards are given each year to bestow upon (the remains of) that individual, who through single-minded self-sacrifice, has done the most to remove undesirable elements from the human gene pool.

22. Darwin was Right
Ladies and Gentlemen...(drum roll...and envelope please)...
We proudly present: Larry Walters, who now (hopefully) realizes the value of knowing some basic meteorology.

23. Darwin was Right
Larry Walters is among the relatively few who have actually turned their dreams into reality.
His story is true (confirmed), though you may find it hard to believe.

24. Darwin was Right
Larry was a truck driver, but his lifelong dream was to fly.
When he graduated from high school, he joined the Air Force in hopes of becoming a pilot.
Unfortunately, poor eyesight disqualified him.

25. Darwin was Right
So when he finally left the service, he had to satisfy himself with watching others fly the fighter jets that crisscrossed the skies over his backyard.
As he sat there in his lawn chair, he dreamed about the magic of flying.

26. Darwin was Right Then one day, Larry Walters got an idea.
He went down to the local army-navy surplus store and bought a tank of helium and forty-five weather balloons.

27. Darwin was Right
These were not your brightly colored party favors, these puppies measured 4 feet across and held 33 cubic feet of helium.
Back in his yard, Larry used straps to attach the balloons to his lawn chair, the kind of chair you have in your own yard.

28. Darwin was Right
He anchored the chair to the bumper of his jeep and inflated 42 of the balloons with helium.
Then he packed some sandwiches, beers and loaded a BB gun, figuring that he could pop a few balloons when it was time to return to earth.

29. Darwin was Right
Preparations complete, Larry Walters sat in his chair and cut the anchoring cord.
His plan was to float slowly upward a few hundred feet, pop a few balloons, and lazily float back down to terra firma.
But things didn't quite work out that way.

30. Darwin was Right
When Larry cut the cord, he didn't float lazily up; he bolted up as if fired from a cannon!
Nor did he go up a couple hundred feet.
He climbed and climbed and climbed until he finally leveled off at 16,000 feet!

31. Darwin was Right
At that height, he feared deflating any of the balloons, lest he unbalance the load and really experience flying!
So he stayed up there, drifting cold and frightened for 14 hours, totally at a loss as to how to get down.

32. Darwin was Right
Eventually, Larry drifted into the approach corridor for Los Angeles International Airport.
A Pan Am pilot radioed the tower about passing a guy in a lawn chair at 16,000 thousand feet with a gun in his lap. (Folks…that's a conversation I'd have given anything to have heard!)

33. Darwin was Right
LAX is right on the ocean, and y’all know at nightfall or aloft during the day, the winds along the coast blow offshore.
As dusk fell, Larry (alledgedly) even drifted out over the ocean for awhile.

34. Darwin was Right
Larry eventually gathered enough nerve to shoot a few balloons and slowly descended.
But as Larry approached the ground, he got entangled in power lines that caused a blackout in Long Beach.
Once on terra firma, he was arrested.

35. Darwin was Right
But as he was being led away in handcuffs, a television reported called out, "Mr. Walters, why'd you do it?"
Larry stopped, eyed the man, then replied nonchalantly, "A man can't just sit around."

36. Darwin was Right (Most of the Time!)
Congratulations Larry, you are a rare survivor to earn (honorable mention) for the prestigious
Darwin “Natural Selection” Award
So, what’s the moral of the story?
If you don’t learn basic meteorology, then you too will be strategically positioned to receive the
Darwin "National Selection" Award

37. Summary Land-Sea Breeze Due to differential heating between land-sea
Gives diurnal reversal in temperature contrast
Onshore winds PM - Offshore winds AM Sea Breeze PM - Land Breeze AM
Mountain-Valley Breeze
Differential heating along mountain slopes Gives diurnal reversal in temperature contrast Upslope winds PM - Downslope winds AM Valley Breeze PM - Mountain Breeze AM

38. Next Lecture Monsoon Circulations-Seasonal Winds Asia Monsoon
“Arizona” Monsoon

39. Assignment for Next Lecture
Reading – Ahrens pg
Problems - 7.5