Lab 6

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Lab 6 Atms 4320 / 7320

• On the use of isentropic maps in weather analysis
  and forecasting I.

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Lab 6 - On the use of isentropic maps in weather
analysis and forecasting I.

• Concept of Isentropic Analysis and interpretation
  I. SLU method. Well examine this week, and
  next week well 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.

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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!

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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.

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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.

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Lab 6 - On the use of isentropic maps in weather
analysis and forecasting I.

• Lets start with w, which is vertical motion in
  x,y,p coords.
• Ok, in x,y,q coords we express as (well see this
  later when we talk of coord transformations).

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Lab 6 - On the use of isentropic maps in weather
analysis and forecasting I.

• The equation
• (1) (2) (3)

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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

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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)

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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.

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Lab 6 - On the use of isentropic maps in weather
analysis and forecasting I.

• Integrate from q level 1 to q level 2.

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Lab 6 - On the use of isentropic maps in weather
analysis and forecasting I.

• Aha, now rearrange and look at new LHS

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Lab 6 - On the use of isentropic maps in weather
analysis and forecasting I.

• Then insert into our initial equation and
• Viola!

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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.

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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.

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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.

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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.

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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?

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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

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Lab 6 - On the use of isentropic maps in weather
analysis and forecasting I.

• The end!
• Assignment time!