Bay Area Earth Science Institute (BAESI)

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# Bay Area Earth Science Institute (BAESI) - PowerPoint PPT Presentation

Bay Area Earth Science Institute (BAESI). Pressure San Jose State University, January 24, 2004 http://www.met.sjsu.edu/baesi/. *. Q: What drives the weather in the atmosphere? Q: What causes the weather to change? We must analyse the predominant forces in the atmosphere, namely:

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## Bay Area Earth Science Institute (BAESI)

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Presentation Transcript
1. Bay Area Earth Science Institute (BAESI) Pressure San Jose State University, January 24, 2004 http://www.met.sjsu.edu/baesi/ Weather and Climate

2. Weather and Climate

3. *

4. Q: What drives the weather in the atmosphere? Q: What causes the weather to change? We must analyse the predominant forces in the atmosphere, namely: pressure and pressure gradients, gravity rotation of the earth friction Principle forces Weather and Climate

5. Pressure • Measured in millibars (mb) or inches of mercury • Surface Pressure: Sea level pressure: 1012 mb or 29.9 in of mercury Weather and Climate

6. Temperature change Density change Formally, the equation of state describes this relationship: p=RT p-Pressure (Pa)  - density (g m-3) R - Gas Constant (287 J K-1 kg-1) T - Temperature (K) What causes pressure to change? Weather and Climate

7. Determines the direction and speed of winds Can help explain general circulation of atmosphere. General guidelines: High pressure: clear skies/fine weather Low pressure: cloudy skies/changeable weather Why is this? Pressure Differences Weather and Climate

8. Weather and Climate

9. Weather and Climate

10. Pressure Gradient Force Weather and Climate

11. Coriolis Force Weather and Climate

12. The rotation of the Earth • Rockets, migrating birds, and large scale weather systems are all deflected due to the rotation of the Earth. • The Earth’s rotation causes • Rotational movement that deflects the winds. • The Coriolis Force is the name of this rotational force that deflects motion. Weather and Climate

13. Coriolis Force • Affects direction, not speed of object • Maximum at the poles • Zero at the equator Always acts to the right of the motion in Northern Hemisphere. Always acts to the left of the motion in the Southern Hemisphere. Weather and Climate

14. Geostrophic Wind Northern Hemisphere Weather and Climate