Weather and Climate
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Weather and Climate

NotesLAST WEEK OF FORECASTING ! ! !• Enter forecasts this week for TOP (Topeka, KS)before 7PM (0000 UTC)• We will begin collecting forecasting logs onThursday. We will only accept bound (clipped)logs with your name and date on each sheet andpages in chronological order. Put your forecasterID on the top sheet.• Turn in logs for TUS, ACY, RAP, TOP only. (A-E); (F-K); (L-P); (Q-Z)• Reading: Martin (pages 48- 54)

Weather and Climate(Lecture 22)Instructor: Prof. Michael C. MorganTeaching Assistant: Dianna N. Nelson

Questions from last lecture

When analyzing isobars on a surface map,the pressure used isA. mean-sea level pressureB. station pressure

The pressure gradient forceA. is directed parallel to isobars.B. is directed from high pressure to low pressure.C. is directed from low pressure to high pressure.

Pressure gradient force

The magnitude of the pressure gradientforce is ____ the closer the isobars are toone another.A. higherB. lower

Map discussionhttp://weatherbonk.com

Imagine that you are on theNorth PoleYou want to launch an object towardsMadison, in which direction should youaim?Hint: Will Madison be in the same place bythe time the object gets there?

Coriolis force• The Coriolis force modifies the wind.• All free moving objects or fluids in thenorthern hemisphere are deflected to theright.• In the southern hemisphere they aredeflected to the left.• The Coriolis effect is result of the earthspinning.


The Earth’s spin• The N. Hemisphere spins counterclockwise The Coriolis deflects to theright• The S. Hemisphere spins clockwise Coriolis deflects to the left• The wind is deflected by Coriolisdifferently in each hemisphere.

Coriolis Effect

Coriolis force at the equator• Coriolis force is zero at the equator!• However, as soon as an object moves justa little off of the equator, coriolis will acton it.

Coriolis effect

Coriolis and pressure gradient force are balanced

Curved Winds

Winds aloft• Winds that are not influenced bysurface friction and therefore behave asgeostrophic winds and gradient winds.• To look at winds at upper levels we lookon constant pressure charts.– i.e. 850mb, 700mb, 500mb, 250mb charts• These charts are at a constant pressurelevel, and have contours of height.

A constant pressure surfacemay have different heights.

Air aloft

Ridges and troughs

SFC vs. aloftAt the surface wemust now considerfriction!•Another example

Surface flow

Southern Hemisphere• How would the winds flow around highsand lows in the Southern Hemisphere?

Convergence and divergence

Convergence and divergence

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