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Review For Exam 3

GEOL 1350: Introduction To Meteorology

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Exam 3

Where: SEC 100

When: 1:00 pm - 2:30 pm, Mar 18 (Tuesday)

Lectures 9-12

Close-book Exam. Exam counts 20% of the total grade.

You need bring a pencil and a eraser to fill the Scantron (Answer Sheet). We will hand out exam and Scantron.

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Raindrop formation in warm clouds

In warm clouds (clouds with above freezing temperatures at all levels, mostly low clouds), cloud droplets grow into raindrops by a process called Collision and Coalescence

  Collision – small cloud droplets join together by random collisions

  Coalescence – Large and faster moving cloud droplets overtake smaller and slower drops in their path to form larger droplets

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Surface High and Low Pressure and Winds Near surface in the Northern Hemisphere, winds blow counter clockwise around and towards a low pressure center

Clockwise around and outwards from a high pressure center

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•  Magnitude CENTF = mV2/R – m is the mass – R the radius of curvature of the curved path – V is the speed of the air parcel

•  Direction – Pointing away from the center of the curve – The faster the speed and the tighter the curve of the path traveled (i.e., the smaller R), the larger the centrifugal force.

Centrifugal Force

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Frictional Force •  Frictional drag of the ground slows wind down. FF = -kV

–  Magnitude •  Depends upon the speed of the air parcel (V) •  Depends upon the roughness of the earth’s

surface (k) –  Direction

•  Always acts in the direction opposite to the movement of the air parcel (minus sign emphasizes this)

–  Important in the friction layer (planetary boundary layer) •  ~lowest 1000 m of the atmosphere

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Scales of

Motion •  Microscale: meters to 1 km

–  Turbulent eddies •  Lifetimes of minutes

•  Mesoscale: 1 km to 200 km –  Local winds and circulations

•  Land/sea breezes, mountain/valley winds, thunderstorms, tornadoes •  Lifetimes of hours to a day

•  Synoptic scale: 200 km to 2000 km –  Hurricane, tropical storms, lows and highs, fronts, everyday weather

•  Lifetimes of days to weeks

•  Planetary scale: > 2000 km, weeks, longwaves in westerlies

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At night, temperature is lower over land due to stronger radiative cooling of the land surface. The temperature difference produces pressure difference with higher pressure over land. The pressure difference produces a land breeze circulation with air flowing towards ocean near the surface and return flow aloft