55 lines
1.9 KiB
Python
55 lines
1.9 KiB
Python
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##
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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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# ----------------------------------------------------------------
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# Calculates the heatIndex from temperature(C) and dewpoint temperatures(C)
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# ----------------------------------------------------------------
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import numpy
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from numpy import power
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const1 = 0.0091379024
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const2 = 6106.396
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def calculate(T, DpT):
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# T and DpT have to be in C for the below calculation
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badValue = numpy.where(T < 26.5,1,numpy.where(DpT > T,1,0))
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TK = T + 273.15
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DpTK = DpT + 273.15
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# Legacy src/meteoLib/calcrh.f
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exponent = numpy.where(T < 80.0, const1 * (TK - DpTK) + const2/TK - const2/DpTK,const1 * (T - DpT) + const2/T - const2/DpT)
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RH = 100 * numpy.exp(exponent)
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T1 = (T * 1.8) + 32
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T1_sq = T1 * T1
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RH_sq = RH * RH
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# the Lans Rothfusz formula
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H1 = -42.379 + (2.04901523 * T1) + (10.14333127 * RH)
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H2 = (-0.22475541 * T1 * RH) - (0.00683783 * T1_sq) - (0.05481717 * RH_sq)
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H3 = (0.00122874 * T1_sq * RH) + (0.00085282 * T1 * RH_sq)
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H4 = (-0.00000199 * T1_sq * RH_sq)
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Hi = H1 + H2 + H3 + H4
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HiC = (Hi - 32) / 1.8 #convert F to C
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#Returned in Celsius
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return numpy.where(badValue == 1, -9999.0, HiC)
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