CALHEL2.f File Reference

Subroutine that computes storm relative helicity. More...

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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]	LLOW	Lower bound CAPE>=100 and CINS>=-250.
[in]	LUPP	Upper bound CAPE< 100 or CINS< -250; allows one to distinguish 0-3 km and 0-1 km values.
[in]	DEPTH	Depth in meters over whcih helicity should be computed; allows one to distinguish 0-3 km and 0-1 km values.
[out]	UST	Estimated U Component (m/s) Of Storm motion.
[out]	VST	Estimated V Component (m/s) Of Storm motion.
[out]	HELI	Storm-relative helicity (m**2/s**2).
[out]	CANGLE	Critical 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().