UPP (develop)
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CALHEL2.f File Reference

Subroutine that computes storm relative helicity. More...

Go to the source code of this file.

Functions/Subroutines

subroutine calhel2 (llow, lupp, depth, ust, vst, heli, cangle)
 This routine computes estimated storm motion and storm-relative environmental helicity.
 

Detailed Description

Subroutine that computes storm relative helicity.

Definition in file CALHEL2.f.

Function/Subroutine Documentation

◆ calhel2()

subroutine calhel2 ( integer, dimension(ista_2l:iend_2u,jsta_2l:jend_2u), intent(in)  llow,
integer, dimension(ista_2l:iend_2u,jsta_2l:jend_2u), intent(in)  lupp,
real, dimension(2), intent(in)  depth,
real, dimension(ista_2l:iend_2u,jsta_2l:jend_2u), intent(out)  ust,
real, dimension(ista_2l:iend_2u,jsta_2l:jend_2u), intent(out)  vst,
real, dimension(ista_2l:iend_2u,jsta_2l:jend_2u,2), intent(out)  heli,
real, dimension(ista_2l:iend_2u,jsta_2l:jend_2u), intent(out)  cangle 
)

This routine computes estimated storm motion and storm-relative environmental helicity.

(Davies-Jones et al 1990) the algorithm processd as follows.

The storm motion computation no longer employs the Davies and Johns (1993) method which defined storm motion as 30 degress to the right of the 0-6 km mean wind at 75% of the speed for mean speeds less than 15 m/s and 20 degrees to the right for speeds greater than 15 m/s. Instead, we now use the dynamic method (Bunkers et al. 1988) which has been found to do better in cases with 'non-classic' hodographs (such as Northwest-flow events) and do as well or better than the old method in more classic situations.

Parameters
[in]LLOWLower bound CAPE>=100 and CINS>=-250.
[in]LUPPUpper bound CAPE< 100 or CINS< -250; allows one to distinguish 0-3 km and 0-1 km values.
[in]DEPTHDepth in meters over whcih helicity should be computed; allows one to distinguish 0-3 km and 0-1 km values.
[out]USTEstimated U Component (m/s) Of Storm motion.
[out]VSTEstimated V Component (m/s) Of Storm motion.
[out]HELIStorm-relative helicity (m**2/s**2).
[out]CANGLECritical angle.
Note
The following variables are used within the function but are not input/output.
  • USHR1 U Component (m/s) Of 0-1 km shear.
  • VSHR1 V Component (m/s) Of 0-1 km shear.
  • USHR6 U Component (m/s) Of 0-0.5 to 5.5-6.0 km shear.
  • VSHR6 V Component (m/s) Of 0-0.5 to 5.5-6.0 km shear.

Program history log:

Date Programmer Comments
1994-08-22 Michael Baldwin Initial
1997-03-27 Michael Baldwin Speed up code
1998-06-15 T Black Conversion from 1-D to 2-D
2000-01-04 Jim Tuccillo MPI Version
2000-01-10 G Manikin Changed to Bunkers method
2002-05-22 G Manikin Now allow choice of computing helicity over two different (0-1 and 0-3 km) depths
2003-03-25 G Manikin Modified code to compute mean winds using arithmetic averages instead of mass weighting; differences are minor but want to be consistent with the Bunkers method
2004-04-16 M Pyle Minimal modifications but put into NMM WRFPOST code
2005-02-25 H Chuang Add computation for ARW A grid
2005-07-07 Binbin Zhou Add RSM for A grid
2019-09-03 J Meng Modified to compute effective helicity and critical angle
2021-09-02 Bo Cui Decompose UPP in X direction
Author
Michael Baldwin W/NP2
Date
1994-08-22

Definition at line 48 of file CALHEL2.f.

References exch().

Referenced by miscln().