78 lines
2.7 KiB
Python
78 lines
2.7 KiB
Python
##
|
|
# This software was developed and / or modified by Raytheon Company,
|
|
# pursuant to Contract DG133W-05-CQ-1067 with the US Government.
|
|
#
|
|
# U.S. EXPORT CONTROLLED TECHNICAL DATA
|
|
# This software product contains export-restricted data whose
|
|
# export/transfer/disclosure is restricted by U.S. law. Dissemination
|
|
# to non-U.S. persons whether in the United States or abroad requires
|
|
# an export license or other authorization.
|
|
#
|
|
# Contractor Name: Raytheon Company
|
|
# Contractor Address: 6825 Pine Street, Suite 340
|
|
# Mail Stop B8
|
|
# Omaha, NE 68106
|
|
# 402.291.0100
|
|
#
|
|
# See the AWIPS II Master Rights File ("Master Rights File.pdf") for
|
|
# further licensing information.
|
|
###
|
|
|
|
from numpy import zeros
|
|
import Gradient
|
|
import Vorticity
|
|
|
|
##
|
|
# Calculate the isobaric potential vorticity through a layer.
|
|
#
|
|
# User Notes:
|
|
#
|
|
# 1. Stability is defined as -dP/d(theta). We calculate this through
|
|
# the layer from the isobaric surface 'n' to the surface above it,
|
|
# 'n+1'.
|
|
# 2. Since we are dealing with a layer, we calculate a mean absolute
|
|
# vorticity using the winds at the upper and lower layers.
|
|
# 3. The PV is then [mean abs. vort]/[stability] + theta->pres term
|
|
#
|
|
# originally from pvpres.f, by J.Ramer
|
|
# @change: Converted from Fortran on 2008-16-06
|
|
#
|
|
# @param t_up: Theta on upper isobaric sfc (K)
|
|
# @param t:lo: Theta on this isobaric sfc (K)
|
|
# @param p_up: Upper pressure (mb)
|
|
# @param p_lo: This (lower) pressure (mb)
|
|
# @param Wind_up: tuple(U,V) winds on upper surface (m/s)
|
|
# @param Wind_lo: tuple(U,V) winds on lower surface (m/s)
|
|
# @param dx: Spacing in X direction (m)
|
|
# @param dy: Spacing in Y direction (m)
|
|
# @param coriolis: Coriolis parameters (/s)
|
|
# @return: Isobaric potential vorticity
|
|
# @rtype: numpy array
|
|
def execute(t_up, t_lo, p_up, p_lo, vector_up, vector_lo, dx, dy, coriolis):
|
|
""
|
|
|
|
u_up, v_up = vector_up[2], vector_up[3]
|
|
u_lo, v_lo = vector_lo[2], vector_lo[3]
|
|
|
|
# Calculate the absolute vorticity at each isobaric surface.
|
|
avort1 = Vorticity.execute(u_up, v_up, coriolis, dx, dy)
|
|
avort2 = Vorticity.execute(u_lo, v_lo, coriolis, dx, dy)
|
|
|
|
# Calculate the temperature gradient on each surface.
|
|
grad_lo = Gradient.execute(t_lo, dx, dy)
|
|
grad_up = Gradient.execute(t_up, dx, dy)
|
|
dtdx1, dtdy1 = grad_lo[2], grad_lo[3]
|
|
dtdx2, dtdy2 = grad_up[2], grad_up[3]
|
|
# Calculate difference arrays.
|
|
dp = p_up - p_lo
|
|
dt = t_up - t_lo
|
|
du = u_up - u_lo
|
|
dv = v_up - v_lo
|
|
dtdx = dtdx1 + dtdx2
|
|
dtdy = dtdy1 + dtdy2
|
|
av = avort1 + avort2
|
|
|
|
result = (-0.5 * (av*dt + (du*dtdy - dv*dtdx)) / dp)*.5
|
|
|
|
return result
|
|
|