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http://www.atmos.washington.edu/academics/classes/2013Q1/380/HW5.html Due Thursday Feb 14 |
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In this exercise you will learn about blocking forecasts and their sensitivity to surface boundary conditions. We will be using WRF-ARW for this exercise to simulate the blocking event of winter 2012 in Europe. The code has been modified by experts on polar meteorology, so the code is known as Polar WRF, or PWRF (the ARW is implied). A good fraction of the Arctic is included in our grid, so I wanted the PWRF. The major innovation is that this version allows us to specify sea ice thickness (sea ice fraction can be specified in normal WRF, but the thickness is assumed to be 3 m thick everywhere). You will modify the SST and sea ice thickness for this experiment, to see how it influences blocking. The grid resolution is 40km in the horizontal. The boundary conditions are derived from "analysis" (The GFS forecast model 1 hour after initialization). The domain is quite large, so the runs take ~2 hours each. You will have to analyze your output after class is over. Summary: I. Copy the files you need for this exercise. Modify the initial conditions for sea ice and SST. II. Run WRF III. Create your own custum run IV. Write-up. email Cecilia the result of part (d) for your run by Feb 14, and write up answers to a few questions. I. Copy files and make links Make a directory for this exercise in our class directory area, call it WRFV3. CAUTION: look for dots in the blue text below cd /home/disk/p/atms380/$LOGNAME tar xvf ../PWRFV3_HW5.tar cd PWRFV3 We are going to do a "real" run with WRF, which means the run uses real input rather than idealized data. So you will go to a directory set up for real runs and link to data that I prepared aleady. CAREFUL WITH THE NAMES OF THESE FILES! cd test/em_real ln -sf /home/disk/p/atms380/specialinputs/wrfbdy_d01_HW5 wrfbdy_d01 cp /home/disk/p/atms380/specialinputs/wrfinput_d01_HW5 wrfinput_d01 cp /home/disk/p/atms380/scripts/modify_wrfinput.m . Start matlab and edit run modify_wrfinput.m so the perturbation in SST and sea ice thickness are as follows: Steven SSTanomaly = 5; tinythickness = 0.1; Shane SSTanomaly = 7.5; tinythickness = 0.1; Nate SSTanomaly = 10; tinythickness = 0.1; David SSTanomaly = 5; tinythickness = 0.5; Ali SSTanomaly = 7.5; tinythickness = 0.5; Andrew SSTanomaly = 10; tinythickness = 0.5; Sebastian SSTanomaly = 5; tinythickness = 0; (note this makes no change to the thickness) Jessica SSTanomaly = 7.5; tinythickness = 0; (note this makes no change to the thickness) Adam SSTanomaly = 10; tinythickness = 0; (note this makes no change to the thickness) Notice that SST exists over land. I assume the model ignores it there. After running the modify_wrfinput.m script, check that you made file test.nc in the run directory by listing it. This file is an interum step in modifying the input. test.nc has the perturbed fields in it. CAREFUL WITH THE NEXT STEP You are going to put your perturbed fields into the wrf input file. ONLY DO THIS ONCE! It will take a few seconds. ncks -A test.nc wrfinput_d01 II. Run WRF qsub run-wrf.csh 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 Wait about 5 hours and when qstat indicates you job is no longer in the queue, check to see that you have an output file that is ABOUT this size (hint use ls -l wrfout*) -rw-r--r-- 1 bitz atgstaff 6672465308 Feb 7 08:42 wrfout_d01_2012-01-24_00:00:00 When you are sure your job is done, copy a ncl script to your run directory and run it. This script interpolates output from your run to pressure levels, so you can examine the 500 hPa height. The ncl script makes a new file named wrfout_d01_2012-01-24_00:00:00_plev.nc cd /home/disk/p/atms380/$LOGNAME/PWRFV3/test/em_real cp /home/disk/p/atms380/scripts/get_onplev.ncl . ncl get_onplev.ncl III. Set up your own custum run. Make a NEW directory for a second run. You must use a different directory than above, otherwise you will overwrite your other run. I suggest mkdir /home/disk/p/atms380/$LOGNAME/second cd /home/disk/p/atms380/$LOGNAME/second tar xvf ../../PWRFV3_HW5.tar Now repeat the instructions above but for this new directory. Be careful not to get mixed up! Ask Cecilia for help if you need it. This time modify the input file however you like. I am not sure what will happen if the SST is below zero. It might be fine. It might crash. Welcome to modelling. You must do one thing special for this run. You must edit the run-wrf.csh script to make it run the model in you second run directory. This is critical. When all is ready submit this job too. IV. Analyze WRF - turn in about a page, plus supporting figures. The MATLAB scripts for this exercise and are in a directory named /home/disk/p/atms380/wrf_blocking . Copy them wherever you wish. a) An animation of the analysis for this even can be found at http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?/home/disk/funnel/atmos/academics/classes/2013Q1/380/blocking2012/+all . Watch it a few times. When do you see for the first time 500 hPa heights along a given longitude that are at least 10 decimeters higher to the north of some point along the longitude. Hint, the contour should look a bit "S" shaped. Approximately, how long does the block last? b) Describe your custum run. c) Run plotT.m and plotZ.m The white spots on the Temperature field are where the topography is higher than 850 hPa. These are NaNs or Not A Number in matlab. Rerun these scripts with your output too. Nothing to write up for this part. d) Run euroT.m It makes a temperature timeseries of 850 hPa over Europe. What is the coldest temperature and what is the mean temperature for days 6 through 14? Hint you can use the command line in matlab and type things like min(ET) and mean(ET(21:56)) (check my math). The script is setup to show my output. Change it to instead examine your runs. Send Cecilia your results for run 1 by email so she can report back to the class. e) Copy plotZdiff.m and plotTdiff.m from /home/disk/p/atms380/wrf_blocking to wherever you wish. These scripts should show you the difference between your first run and my control without any perturbations. You can edit them if you want to look at your second run. These may not be super easy to interpret, so we will discuss them in class. Describe in your homework write-up how your first run differs from the control for 500 hPa heights and 850 hPa temperature. Pay particular attention to heights over Iceland, Norway, and Great Britain and temperature over Europe. Write about 200 words.
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