Lab 6 – Atms 4320 / 7320

1. Lab 6 – Atms 4320 / 7320 On the use of isentropic maps in weather analysis and forecasting I.

2. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • Concept of Isentropic Analysis and interpretation I. “SLU” method. We’ll examine this week, and next week we’ll look at SUNYA method. • Supplementary reading: Market et al. (2000) NWD Dec. pp. 31 – 37. • It has become commonplace to examine the atmosphere in x,y,q coordinates.

3. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • If atmosphere is hydrostatic and adiabatic, then as we said in Atms 4310 / 7310 potential temperature is a conserved quantity. • If so, then parcels will follow lines of constant q, or we must consider those parcels to be “tied” to that surface!

4. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • Thus, we can: • 1) examine the motions of that surface with time to infer vertical motions, and • 2) examine the wind fields and infer “upglide” and “downglide” of air parcels.

5. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • This is the “elevator – escalator” concept of looking at atmospheric motions. Recall, we stated that vertical motions are important to examine in synoptics. They are part of the secondary atmospheric circulations.

6. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • Let’s start with w, which is vertical motion in x,y,p coords. • Ok, in x,y,q coords we express as (we’ll see this later when we talk of coord transformations).

7. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • The equation (1) (2) (3)

8. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • Thus, vertical motions are the result of: • Term 1: The change in the location of a pressure surface. • Term 2: The isentropic “upglide” or advection of P on q. + pressure advection  +w

9. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • Term 3: Diabatic Heating (product of Stability and diabatic heating, static stab modulates):

10. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • It had been assumed that terms 1 and 3 cancelled, however, we can show very easily that this is not so: • Start with Continuity in x,y, q.

11. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • Integrate from q level 1 to q level 2.

12. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • Aha, now rearrange and look at new LHS:

13. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • Then insert into our initial equation and: • Viola!

14. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • If we choose level 1 to be our level of interest and level 2 to be above level 1, then the pressure tendency of the above surface will reflect diab. Heating.

15. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • Thus, term 1 cannot completely cancel term 3. Can show the same thing by choosing level 1 to be below you and level 2 to be your level of interest. Then bottom surface will reflect diab. Heating. Typically, though we want to see integrated diabatic heating throughout troposphere.

16. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • The equation: • So there is also that “pesky” integrated stability flux term.

17. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • How to get term 1: Qualitatively? • Simply examine two maps of pressure on a theta surface and infer the change.

18. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • How to get term 2: Qualitatively? • How do you get temperature advection Qualitatively?

19. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • Term 3: can calculate as well, or infer. • Recall for heating: • Cooling:

20. Lab 6 - On the use of isentropic maps in weather analysis and forecasting I. • The end! • Assignment time!