Computer Assignment #6
METR 2413
Assigned: February 23, 2004
Due: March 1, 2004

For Lab 6, you were asked to mark the regions of warm and cold advection using the 1000-500 mb thickness and surface pressure fields. Now you get to calculate directly the temperature advections at 700 mb. You will be using the Gempak program gdcntr again. This one program is one of the most used programs by Gempak for analysis.

From appendix B1 of the Gempak Users Manual, Gempak calculates the advection as follows:

ADV Advection
ADV ( S, V ) = - ( u * DDX (S) + v * DDY (S) )

where S is a scalar quantity and V a vector quantity. In the case of temperature advection, temperature is the scalar and
wind is the vector.

1. Make your own surface pressure and 1000-500 mb thickness map for 00 UTC 20 February 2004, similar to the one handed out for Lab 6. Use the Gempak program gdcntr. Use the grided data files that are found in /data/gempak/model. You may want to transfer your lab analysis onto this map.
   
   
2. Analyze the temperature advections for 00 UTC 20 February 2004 at 700 mb and compare those you have calculated versus those derived from the solenoid method from Lab 6.
   
   
3. Analyze the 06 UTC 20 February 2004 the surface mean sea level pressure field.
   
   Questions:
   
   1. Do the calculated temperature advections and the solenoid temperation advections agree or disagree? Briefly discuss the advantages/disadvantages of the two methods of deriving tempature advections.
      
   2. Briefly discuss the surface low pressure development/propagation as related to the regions of warm and/or cold advection.
      
   3. Turn in all maps needed to answer questions one and two.

Hints:

• Keep in mind that level difference function (ldf) requires two levels to be specified in the glevel parameter.
  
• You may want to use different line types when combining the thickness analysis with the surface pressure analysis.
  
• Breifly discuss means just that no more than 3-4 sentences should suffice.