NATS 101 Lecture 18 Local Winds. Supplemental References for Today’s Lecture Danielson, E. W., J....
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Transcript of NATS 101 Lecture 18 Local Winds. Supplemental References for Today’s Lecture Danielson, E. W., J....
NATS 101
Lecture 18Local Winds
Supplemental References for Supplemental References for Today’s LectureToday’s Lecture
Danielson, E. W., J. Levin and E. Abrams, 1998: Meteorology. 462 pp. McGraw-Hill. (ISBN 0-697-21711-6)
Review: Forces for Curved Flow
5700 m5640 m
Centripetal = CF + PGF
Centripetal << CF or PGF
Gradient Wind Balance
Wind
Wind
Geo
Win
dPGF
PGF
PGF
CF
CF
CF
Assume PGF constant size along entire channel
Trough
Ridge
Sub-geostrophicSub-geostrophic
Super-geostrophicSuper-geostrophic
Divergence and Convergence
Diver
gence
Mas
s Los
s
Convergence
Mass G
ain
Mass transport in channel
Large
Small
Trough
Ridge
Convergence
Convergence Divergenc
Divergencee
DivergenceDivergence
ConvergenceConvergence
Convergence
Convergence
Divergence
Divergence
ConvergenceConvergence
DivergenceDivergence
Gedzelman, p249
Vertical Motion
Mass Conservation leads to Upward motion beneath regions of divergence Downward motion beneath regions of convergence
Trough RidgeRidge
Review: Friction
Pressure Gradient Force
Coriolis Force
Wind
1004 mb
1008 mb
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.
Friction
Gedzelman, p249
Flow at Surface LowsLows and HighsHighs
Spirals OutwardDivergence
Spirals InwardConvergence
www.met.tamu.edu
upward motionupward motiondownward motiondownward motion
Ahrens, Fig 6.21
Friction Induced Vertical Motion
Atmospheric Scales of Motion
Ahrens, Fig 7.1
Review:Thermally Direct Circulation
Heat Heat
WarmWarm ColdColdRisingRising SinkingSinking
DIV
DIV
CON
CON
HeatHeat
Sea Breeze Development(Courtesy of Mohan Ramamurthy, WW2010)
1 2
3 4
Sea Breeze Development(Courtesy of Mohan Ramamurthy, WW2010)
5 6
7
RisingRising SinkingSinking
DIV
DIV
CON
CONHeatHeat
Sea Breeze versus Land Breeze (Courtesy of Mohan Ramamurthy, WW2010)
Stronger Temperature contrast during PM than during AM
Sea breezes are stronger than land breezes
PM
AM
LAX Airport 4 PM upper 7 AM lower
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
Mountain-Valley Breeze
Ahrens, Older Ed.
Sun warms slopes Density decreases Air rises
IR cools slopes Density increases
Air drains
RisingRising SinkingSinking
DIV CON
HeatHeat
CON DIV
Mountain-Valley circulation important to TucsonConvection over Catalinas during PM summer.SE drainage flows during early AM all year.
Phoenix-Tucson Diurnal Winds
5 PM5 AMPM heating
AM cooling
5 PM5 AMPM heating
AM cooling
PMAM TUS TUS
PMAM PHX PHX
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.
www.darwinawards.com
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.
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.
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.
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.
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.
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.
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.
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.
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!
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.
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!)
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.
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.
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."
Darwin was Right(Most of the Time!)
Congratulations Larry, you are a rare survivor to earn (honorable mention) for the prestigiousDarwin “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 theDarwin "National Selection" Award
Summary
• Land-Sea Breeze
Due to differential heating between land-seaGives diurnal reversal in temperature contrastOnshore 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
Next Lecture
• Monsoon Circulations-Seasonal Winds
Asia Monsoon
“Arizona” Monsoon
Assignment for Next Lecture
• Reading – Ahrens pg 173-175• Problems - 7.5