Meteorology 553- Synoptic Meteorology I

Assignment 1 Due: October 14

Purpose: (1) become familiar with compiling, running, and debugging a fortran code that accesses data in gempak format; (2) compute the amplitude and phase of waves 1-10 for the latitude belt 40\60N for a 10-day period from a sequence of MRF forecasts; (3) interpret the variations in amplitude and phase of planetary-scale waves versus synoptic scale waves.

Compiling and running the program

This first assignment does not require writing a program from scratch. There are 3 files required for this assignment: (1) the fortran program (labex1.f); (2) a c-shell script to compile the program (compile_program); and (3) a c-shell script to run the program (labex1.csh). Do the following:

Create a directory in your root directory, called labex, by using the following command: mkdir labex

Move to that directory, by using the command: cd labex

Copy the 3 files to your directory by using the following commands: (1) cp ~gempak/met553/labex1.f . (2) cp ~gempak/met553/compile_program . and (3) cp ~gempak/met553/labex1.csh .

Review the information given in class regarding the details of the program, compilation script, and run-time script. Also review the information given regarding the plotting routine- xgraph.

(1) Compile the program by typing: compile_program labex1

(2) To determine the amplitude and phases of waves 1-10 for the latitude belt 40-60N for October 4, run the program for the first time by typing: labex1.csh

(3) Print out the fraction of variance, phase, and cumulative amplitude of waves 1-10 for the 40-60N latitude belt. To see what the cumulative amplitude should look like, click here. To see what the fraction of variance should look like, click here. To see what the phase should look like, click here.

(4) Describe and evaluate the changes in amplitude as a function of forecast time. You do not need to describe every change during the 10-day period. But, what are the significant changes in the amplitudes of the planetary scale waves during this time both in terms of cumulative amplitude and fraction of the total variance? What waves dominate during different times of the 10-day period?

(5) Describe and evaluate the changes in phase of waves 2 and 6 over the 10-day period. When do the waves retrogress, remain stationary, or progress?

(6) Repeat steps 2-5, for the next day, October 5.

(6) Repeat steps 2-5, for a different latitude range on October 4.

Evaluating the Spatial and Temporal Evolution of Waves

This part of the exercise requires the use of the 9-panel MRF gif files availble on Mosaic on the MRF page and on the Sun workstations using xanim.

Look and familiarize yourself with the current 9-panel MRF gif files available on Mosaic and thru the menu on the sun workstations.

Access the panels for the assignment by typing: xanim /home/mirage/u/gif/nmc/mrf/MRF_WA_941004*.gif

Step thru the 10-day evolution of the waves and respond to the following:

(1) At what time during the 10 day period is the zonally averaged zonal wind likely to be strongest in the 40-60N latitude belt? According to linear Rossby wave theory, when do you expect planetary scale waves to retrogress? When the zonally averaged zonal flow is weak or strong?

(2) Estimate the value (in m/s) of the zonally averaged zonal wind in the latitude belt 40-60 N at the initial time and at the 120 hour forecast time. From this value and linear Rossby wave theory, estimate the stationary wave number at these 2 times.

(3) Are each of waves 1-5 tending to retrogress, remaining stationary, or progressing during the 10-day period? How does the model's evolution compare to that predicted from Rossby wave theory in this case?

(4) Compare and contrast the evolution of cumulative waves 0-5 and 0,6-10 to the total height field. What wave numbers contribute primarily to the cut-off low over the western U.S. at the initial time?

Send your written response to this assignment to me by e-mail to jhorel@atmos.met.utah.edu.

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