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19991129: GEMPAK's Virtual Potential Temperature Calculations

Lisa,

The virtual potential temperature uses virtual temperature TVRK
which provides:
$GEMPAKHOME/source/gemlib/pr/prtvrk.f
   PR_TVRK  ( TMPC, DWPC, PRES )

--> TVRK = TMPK * (1 + .001 * MIXR / .62197) / (1 + .001 * MIXR)

Where MIXR is obtained from:
   PR_MIXR  ( DWPC, PRES )

The mixing ratio is calculated from DWPC and PRES. If the air is saturated,
then DWPC = TMPC, and therefore the mixing ratio is the saturated mixing
ratio. That is, if your environment is saturated, then TMPC=DWPC,
and therefore MIXR = MIXS.

Steve Chiswell
Unidata User Support



>From: "lisashoe" <address@hidden>
>Organization: .
>Keywords: 199911292313.QAA20380

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>My name is Capt Lisa Shoemaker, and I'm a graduate meteorology student =
>at the Air Force Institute of Technology, OH.  I have a question =
>concerning the virtual potential temperature calculation in GEMPAK.  I =
>have reviewed the formula in the AWIPS user's guide that somewhat =
>explains GEMPAK's calculation of virtual potential temperature, and I =
>noted that mixing ratio is one of the parameters included.  Does GEMPAK =
>account for a saturated environment in its virtual potential temperature =
>calculation (i.e., does it automatically use the saturation mixing ratio =
>instead of just mixing ratio)?   My reason for asking is that I am doing =
>research concerning the boundary layer, and I'm using plots of virtual =
>potential temperature versus height (via the SNPROF program) to aid in =
>my analysis.  =20
>
>Can you clarify the virtual potential temperature calculation?
>
>Thanks in advance for your help,
>
>Lisa C. Shoemaker, Capt, USAF
>Master's Candidate, Air Force Institute of Technology
>
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><DIV><FONT face=3D"Comic Sans MS" size=3D2>My name is Capt Lisa =
>Shoemaker, and I'm a=20
>graduate meteorology student at the Air Force Institute of Technology, =
>OH.&nbsp;=20
>I have a question concerning the virtual potential temperature =
>calculation in=20
>GEMPAK.&nbsp; I have reviewed the formula in the&nbsp;AWIPS user's guide =
>that=20
>somewhat explains GEMPAK's calculation of virtual potential temperature, =
>and I=20
>noted that mixing ratio is one of the parameters included.&nbsp; Does =
>GEMPAK=20
>account for a saturated environment in its virtual potential temperature =
>
>calculation (i.e., does it automatically use the saturation mixing ratio =
>instead=20
>of just mixing ratio)?&nbsp;&nbsp; My reason for asking is that I am =
>doing=20
>research concerning the boundary layer, and I'm using plots of virtual =
>potential=20
>temperature versus height (via the SNPROF program) to aid in my=20
>analysis.&nbsp;&nbsp; </FONT></DIV>
><DIV>&nbsp;</DIV>
><DIV><FONT face=3D"Comic Sans MS" size=3D2>Can you clarify the virtual =
>potential=20
>temperature calculation?</FONT></DIV>
><DIV>&nbsp;</DIV>
><DIV><FONT face=3D"Comic Sans MS" size=3D2>Thanks in advance for your=20
>help,</FONT></DIV>
><DIV>&nbsp;</DIV>
><DIV><FONT face=3D"Comic Sans MS" size=3D2>Lisa C. Shoemaker, Capt,=20
>USAF</FONT></DIV>
><DIV><FONT face=3D"Comic Sans MS" size=3D2>Master's Candidate, Air Force =
>Institute=20
>of Technology</FONT></DIV></BODY></HTML>
>
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