Local Winds By Diana L. Duckworth Rustburg High School Campbell County, VA.
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Transcript of Local Winds By Diana L. Duckworth Rustburg High School Campbell County, VA.
Local Winds
ByDiana L. Duckworth
Rustburg High SchoolCampbell County, VA
land oceanHOT COOL
LOW HIGH
• Ocean has high heat capacity; cooler in day than land (low heat capacity); becomes HIGH
• Land is warmer in day - becomes a LOW• Sea Breeze in daytime from ocean to land;
affects coastal areas only
Sea Breeze
Note the cloudsformed inland fromcoastline.
Clouds form whereair rises.
Evidence of seaBreeze
Photo from EOS
land oceanCOLDWARM
LOWHIGH
Land Breeze
• Land is colder at night; becomes a HIGH
• Ocean is warmer at night; becomes a LOW
• Land breeze develops at night as air moves in coastal areas from high over land to low over the ocean.
Note 24 hour cycle in wind direction - Station on Oregon coast; easterly in night; northwesterly in day.
Figure from National Data Buoys website
mountain
valley
CoolHIGH
Warm LOW
Valley Breeze
• Thin air heats & cools more rapidly than dense air– Dense air in valley remains cooler in day & becomes
high pressure– Thin air in mountains warms and becomes a low
pressure
• Air flows up from the valley in a valley breeze
Note clouds formed over the mountain ranges where air is rising.
Astronaut Photo
mountain
valley
HIGH
LOW
Mountain Breeze
• At night, thin air cools rapidly becomes high in mountains
• Dense air in valleys retains heat; becomes a low
• Air flows down the mountain from high to low in a Mountain Breeze
Cyclones & Anticyclones
Small Scale Pressure Systems
Coriolis Effect
• Objects moving over the surface of the earth are affected by Earth’s rotation
• Northern Hemisphere, path curves to object’s right
• Southern Hemisphere, path curves to object’s left
• Speed of Earth’s rotation decreases as latitude increases
• Effect greater at Poles than Equator
LOW
Northern Hemisphere Cyclone Map View
Air converges into a Low
LOW
Coriolis Effect turns Wind to Right
PressureMakes AirConvergeInto aLOW
Coriolis EffectTurns air to theRight
COUNTERCLOCKWISE AROUND A CYCLONE
Anticyclone in Northern Hemisphere – Map View
HIGH
Air DivergesFrom a HIGH
Anticyclone in Northern Hemisphere – Map View
HIGH
Air DivergesFrom a HIGH
Coriolis Effect turns air to the right.
WIND BLOWS CLOCKWISE AROUND A HIGH
Northern Hemisphere
LOW HIGH
COUNTERCLOCKWISE CLOCKWISE
Southern Hemisphere Opposite
LOW HIGH
CLOCKWISE COUNTERCLOCKWISE
Friction with ground slows wind down
• Surface winds do not blow at right angles to
pressure gradient; blow more like 45°
So wind spirals into a low and out from a high at ground level
In Conclusion for Northern Hemisphere
• There are three components of motion of air in a LOW (cyclone)– Spirals inward– Rises– Spirals counterclockwise
• There are three components of motion of air in a HIGH (anticyclone)– Spirals outward– Sinks– Sprials clockwise