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Simulating Milankovitch Cycles

Simulating Milankovitch Cycles. Derek Fox Client: Prof. Hollocher - geology dept. Advisor: Prof. Hemmendinger. What’s with the name?. Named after the Serbian mathematician Milutin Milankovitch who first computed the cycles Lived from 1879-1958. Milankovitch Cycles – What are They?.

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Simulating Milankovitch Cycles

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  1. Simulating Milankovitch Cycles Derek Fox Client: Prof. Hollocher - geology dept. Advisor: Prof. Hemmendinger

  2. What’s with the name? • Named after the Serbian mathematician Milutin Milankovitch who first computed the cycles • Lived from 1879-1958

  3. Milankovitch Cycles – What are They? • Consist of three astronomical cycles of the earth: • Eccentricity of Earth’s orbit • Axial tilt of the earth (Obliquity) • Precession of the equinoxes

  4. Eccentricity • Eccentricity is the amount of which an orbit is elliptical rather than circular Earth’s eccentricity is currently very slight • Varies between .01 and .07 eccentricity • Changes over a period of a period of approximately 100,000 years

  5. Obliquity – Change in Axial Tilt • Current axis is 23.5° • Varies between 22.1° and 24.5° • Changes over a period of 40,000 years • Greater tilt = more severe seasons • Lesser Tilt = milder seasons Looks like a small variation but can have a great effect on seasons

  6. Precession of Equinoxes • The Earth slowly wobbles as it spins on axis (like a top before it falls) • Changes over a period of 23,000 years

  7. Milankovitch Cycles – How Does it Affect Climate? • They determine the amount of solarinsolation that reaches the latitudes of the Earth at a given time of year • Insolation = Solar radiation that strikes the Earth (W/m^2) • The cycles have been correlated to the advance and retreat of glaciers during ice ages

  8. Scientific Verification of Milankovitch Cylces • Verified in 1976 study after examination deep-sea sediment cores • Able to extract the record of temperature change going back 450,000 years • Ice ages had occurred when the Earth was going through different stages of orbital variation.

  9. Program Requirements • Implement Milankovitch mathematics to visually simulate how solar insolation varies as the three cycles change • Have graphs that show the insolation change for specific latitudes over time • Have a model of the earth showing the insolation change at all latitudes • Make it usable by Geology students in intro classes

  10. Program Design • Use Java- swing for the graphical user interface • Java is compatible across multiple platforms • Swing provides convenient graphics • Get the applet onto the web for easy access

  11. Graphical Interface • User Inputs • Latitude • Duration • Month • Step Size • Inclination • Eccentricity • Precession

  12. Coloring the Earth The earth on the previous slide is really a many-sided polygon instead of an oval. Why? Easier to color by breaking the polygon into smaller, 4-sided polygons. I used 180 smaller polygons each corresponding to a degree of latitude. Example using a decagon If the polygons are small enough, the result is a smooth color transition

  13. Class Diagram • Milankovitch- the main applet class which builds the GUI and • GetPoints- calculates the points on the Polygon. • Polys- Breaks down the polygon into the smaller polygons for coloring • Polygon1- Extension of the Java Polygon class to hold insolation and color values for each polygon • Values- works with the Milankovitch equations to determine the insolation.

  14. Using Threads • Problem: Initially, when I tried to animate the graphing and color changes, Java would only update the display after the simulation was complete, only showing the final state • Putting the custom painted swing objects in a separate thread solved this. • Also fixed the problem where the simulation couldn’t be stopped once it had started.

  15. Coloring Issues • It was somewhat difficult to get smooth color transition from low insolation amounts to high insolation amounts. • I used a java applet that let me specify the hue, saturation and brightness and it gave me the proper R,G,B value. Low insolation High insolation The color range I chose

  16. The Mathematics • Equations were derived by Andre Berger in the 1970s • Three different Equations are used • One for the latitudes where there is a sunrise and sunset • Another for when there is no sunset (Arctic summer) • A third for when there is no sunrise (Arctic winter) • I didn’t realize this until I saw that my program didn’t work for latitudes in the Arctic/Antarctic circle.

  17. Conclusion • I accomplished what I set out to do and incorporated the features requested. • The program should be useable by students learning about Milankovitch cycles in Geology. • Currently on the web at: http://antipasto.union.edu/~foxd/hw/project1

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