6d8adaccb2
Change-Id: I7ea007f0f919017e8212716cc15712c7ed611e69 Former-commit-id:8b23f32311[formerlyee11e5d13c] [formerly8b23f32311[formerlyee11e5d13c] [formerlyac33fb9463[formerly a8bcec4a2fa9ddd49dc300ebd63aebfdfb41723e]]] Former-commit-id:ac33fb9463Former-commit-id:b2b2136868[formerlybe163ebf2a] Former-commit-id:182a717b00
87 lines
3.1 KiB
Python
87 lines
3.1 KiB
Python
##
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# This software was developed and / or modified by Raytheon Company,
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# pursuant to Contract DG133W-05-CQ-1067 with the US Government.
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#
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# U.S. EXPORT CONTROLLED TECHNICAL DATA
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# This software product contains export-restricted data whose
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# export/transfer/disclosure is restricted by U.S. law. Dissemination
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# to non-U.S. persons whether in the United States or abroad requires
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# an export license or other authorization.
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#
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# Contractor Name: Raytheon Company
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# Contractor Address: 6825 Pine Street, Suite 340
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# Mail Stop B8
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# Omaha, NE 68106
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# 402.291.0100
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#
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# See the AWIPS II Master Rights File ("Master Rights File.pdf") for
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# further licensing information.
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#
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# Software History
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#
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# 2013/1/17 DR 15655 Melissa Porricelli Modified final 'result'
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# calculation to remove multiplication
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# by 0.5. Displayed values were
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# off by a factor of this amount
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# in comparison to A1.
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# A1 calc in pvpres.f.
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###
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from numpy import zeros
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import Gradient
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import Vorticity
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##
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# Calculate the isobaric potential vorticity through a layer.
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#
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# User Notes:
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#
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# 1. Stability is defined as -dP/d(theta). We calculate this through
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# the layer from the isobaric surface 'n' to the surface above it,
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# 'n+1'.
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# 2. Since we are dealing with a layer, we calculate a mean absolute
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# vorticity using the winds at the upper and lower layers.
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# 3. The PV is then [mean abs. vort]/[stability] + theta->pres term
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#
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# originally from pvpres.f, by J.Ramer
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# @change: Converted from Fortran on 2008-16-06
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#
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# @param t_up: Theta on upper isobaric sfc (K)
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# @param t:lo: Theta on this isobaric sfc (K)
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# @param p_up: Upper pressure (mb)
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# @param p_lo: This (lower) pressure (mb)
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# @param Wind_up: tuple(U,V) winds on upper surface (m/s)
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# @param Wind_lo: tuple(U,V) winds on lower surface (m/s)
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# @param dx: Spacing in X direction (m)
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# @param dy: Spacing in Y direction (m)
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# @param coriolis: Coriolis parameters (/s)
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# @return: Isobaric potential vorticity
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# @rtype: numpy array
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def execute(t_up, t_lo, p_up, p_lo, vector_up, vector_lo, dx, dy, coriolis):
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""
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u_up, v_up = vector_up
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u_lo, v_lo = vector_lo
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# Calculate the absolute vorticity at each isobaric surface.
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avort1 = Vorticity.execute(u_up, v_up, coriolis, dx, dy)
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avort2 = Vorticity.execute(u_lo, v_lo, coriolis, dx, dy)
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# Calculate the temperature gradient on each surface.
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grad_lo = Gradient.execute(t_lo, dx, dy)
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grad_up = Gradient.execute(t_up, dx, dy)
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dtdx1, dtdy1 = grad_lo
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dtdx2, dtdy2 = grad_up
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# Calculate difference arrays.
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dp = p_up - p_lo
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dt = t_up - t_lo
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du = u_up - u_lo
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dv = v_up - v_lo
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dtdx = dtdx1 + dtdx2
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dtdy = dtdy1 + dtdy2
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av = avort1 + avort2
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result = (-0.5 * (av*dt + (du*dtdy - dv*dtdx)) / dp)
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return result
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