[gradsusr] Trouble Calculating ThetaE

Corby Dickerson - NOAA Federal corby.dickerson at noaa.gov
Wed May 7 18:57:42 EDT 2014


Greetings!

I have written the following script to calculate ThetaE from NARR data
using a new formula referenced in Volume 137 of AMS's Monthly Weather
Review. The script runs successfully and displays data which makes sense.
However it plots the same values of ThetaE no matter what level I choose. I
am hoping someone out there will be able to provide me with some direction
as to what I might be doing wrong.

Thanks in advance for the help!

******************************************************************************************************************************************
*Script to calculate Equivalent Potential Temperature referencing equation
6.5 from
*Davies-Jones' September 2009 Monthly Weather Review findings On Formulas
for Equivalent
'open narr.ctl'
'set lat 30 55'
'set lon -140 -100'
*First calculate 2m Dew Point Temperature
*
'define tc2m = TMP2m - 273.15'
'define B = (log(RH2m/100)+((17.27*tc2m)/(237.3+tc2m)))/17.27'
'define TdC2m = (237.3*B)/(1-B)'
'define dewp2m = TdC2m + 273.15'
*
*Then we can calculate Temperature at LCL [K]
'define templcl=(((1/(1/(dewp2m-56)+log((tmp2m/dewp2m))/800))+56))'
*
*And calculate the Pressure at LCL
'define preslcl=(pressfc*pow(((templcl+273.16)/tmp2m),(7/2)))/1000'
*
*With this data in hand we can calculate Potential Temperature at LCL *(K)
*Saturation Vapor Pressure (mb)=6.112 * exp[17.67(Tk-C)/(Tk-C+243.5)]
*
'define eslcl = 6.112*exp((17.67*(templcl-273.15))/(templcl-273.15+243.5))'
*
'define thetaLCL = templcl*pow(1000/(lev-eslcl),0.2854)'
*
*Calculate Equivalent Potential Temperature (ThetaE)
*Define constants
*
'define L0 = 2501000'
'define L1 = 1754'
'define L3 = L0 - L1'
'define K2 = 1137000'
'define cpd = 1105.7'
'define C = 273.15'
'define mythetae =
thetaLCL*exp((L3*(tmpprs-C)+(K2*ICMRprs))*ICMRprs/(cpd*templcl))'

*C. Corby Dickerson IV*
-General Forecaster-
Weather Story Program Manager
*406-329-4840*
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