|
http://www.atmos.washington.edu/academics/classes/2013Q1/380/HW6.html Due Thursday Feb 21 |
|
In this exercise you will learn about how fortunate we are to have a well behaved planet. Since we know very little about the geography of planets in other solar systems, it is typical to use an idealized model to study exoplanets. We will use a sophisticated atmospheric GCM coupled to a Slab Ocean Model (SOM), which has a fixed 50 m depth. There is no land and no topography. For simplicity we will assume the planet's radius and surface pressure are as for Earth. The atmospheric composition is like on Earth, with water vapor concentration depending on temperature and cloud processes. The distance between the planet and its sun is assumed to be as on Earth. You will do a run with a unique obliquity. Obliquity is the angle of the planet's spin axis relative to the normal direction of the planet's orbital plane. Earth has an obliquity of about 23 degrees. Your runs will take about a day to complete. I have already run a set of runs at 0, 30, 60, and 90 for you to analyze in class. The questions you will answer in part II only depend on these completed runs. Cecilia will collect additional results from all of the runs and show results in class. Summary: I. Build and Run CAM (~5 min, plus a long wait time) II. Meanwhile analyze CAM output from runs Cecilia has done aready. I. Build and Run CAM. Name Your obliquity Case directory Bitz 0 /home/disk/p/atms380/bitz/camruns/somplanet Ali 10 /home/disk/p/atms380/acg23/camruns/tilted10 Andrew 20 /home/disk/p/atms380/andrewho/camruns/tilted20 Bitz 30 /home/disk/p/atms380/bitz/camruns/tilted30 Sebastian 35 /home/disk/p/atms380/sebass63/camruns/tilted35 Steven 40 /home/disk/p/atms380/sjbrey/camruns/tilted40 Shane 45 /home/disk/p/atms380/shanep3/camruns/tilted45 Nate 50 /home/disk/p/atms380/ni22/camruns/tilted50 Jessica 55 /home/disk/p/atms380/jcaubre/camruns/tilted55 Bitz 0 /home/disk/p/atms380/bitz/camruns/tilted60 Adam 70 /home/disk/p/atms380/aewisch/camruns/tilted70 David 80 /home/disk/p/atms380/davidyun/camruns/tilted80 Bitz 90 /home/disk/p/atms380/bitz/camruns/tilted90 Fill in the YY below with the number in the table above cd /home/disk/p/atms380/$LOGNAME/camruns mkdir tiltedYY cd /home/disk/p/atms380/$LOGNAME/camruns/tiltedYY cp /home/disk/p/atms380/scripts/bld-tiltedXX.csh . Edit your bld-tiltedXX.csh script to set the obliquity to your number. You can leave the script name as is, or rename it as you like. If you rename it, you may need to make it executable with "chmod 755 bld-whatever.csh", but if you keep the same name, it should already be executable. Then run the script, bld-tiltedXX.csh Wait ~5 minutes. Ignore the warning at the end. When done submit the job. qsub run-cam.csh Verify your job is in the queue with either qstat qstat -u "*" the latter lets you see all the jobs in the queue. If for some reason you wish to kill your job. qdel xxxxx fill in the x's with the job-ID and this will cancel your job II. Analyze CAM, to turn in. Begin your homework write-up with a paragraph explaining the purpose of this exercise. You may need to do each step first. Make a supdirectory for this exercise's analysis files. Maybe you would like to call it "weirdplanets". Go to that directory and copy the analysis files to your directory for this exercise. Start matlab cp /home/disk/p/atms380/scripts/ex5* . cp /home/disk/p/atms380/scripts/hov* . cp /home/disk/p/atms380/scripts/globmean.ncl . matlab & a) Run ex5_a.m in matlab and choose Earth. Ah! The home planet - with continents, mountains, and the right obliquity. Look at your favorite variables. For sure, check out the surface temperature (T), sea ice fraction (I), precipitation (p), and vertical profiles of T and the zonal wind (U). Notice the red "eyes" looking at you for U plotted in the vertical (height-latitude plot). Their centers should be at about 200hPa and they vary in position and intensity with season. There is only one year of a climatology for the Earth run. Run hovmuller.m and choose Earth and check out T and U. This figure helps you quickly see the location of the maxima in time and latitude. Now repeat your survey for the aqua planets with tilt as provided. There is more than one year of data so you can examine interannual variability and trends, as well as the seasonality. To turn in: Compare and constrast the vertical structure of the jet via U with the vertical structure of temperature T for the aquaplanet runs of 0, 30, 60, 90 tilt. Don't worry about trying to understand Earth. It is complicated by mountains and a more complex orbit. Some additional quesions to answer specifically: Which run has the greatest range in seasonal cycle of surface temperature at the poles? At the equator? Which run has the largest magnitude westerly wind at any latitude at 226 hPa (use the Hovmuller plot)? Does it surprise you to know that the timestep has to be lowered as obliquity is raised? Make a table with the obliquity varying by row and with columns for 1) Maximum magnitude of the westerly winds anywhere on the planet 2) Pole to equator temperature difference at the surface 3) Maximum precipitation rate on the planet Feel free to edit the scripts to include other runs that were done by the class. They should finish by the weekend. It might be nice to fill in some of the gaps. This is optional. It is good practice with MATLAB though. b) Next compute the global mean temperature and northern hemisphere sea ice area.First we will do it for the zero obliquity (called somplanet) run. You will edit the script and make it read other runs. Run these commands IN A TERMINAL NOT IN MATLAB: ncl < globmean.ncl This will create a couple of files like Tglob_somplanet.txt, icenh_somplanet.txt Read them into matlab by hand with "load Tglob_somplanet.txt". Plot in matlab with plot(Tglob_somplanet). To turn in: Describe global mean temperature and hemspheric sea ice area for the somplanet run. Do the same for tilted30, tilted60, and tilted90 runs. To your table, add an estimate of the global mean temperature on the annual mean from near the end of the run. Make a note if they do not appear to be equilibrated. Make scatter plots of the data in your table for obliquity on the x-axis and each column on the y-axis of a separate plot. Are the relationships linear? Your write-up should be about one full page of text describing your work with extra pages for the tables and figures.
|
| Return to Homepage |