CALHEL3.f File Reference

Subroutine that computes storm relative helicity. More...

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Functions/Subroutines
subroutine	calhel3 (llow, lupp, ust, vst, heli)
	This routine computes estimated storm motion and storm-relative environmental helicity.

Detailed Description

Subroutine that computes storm relative helicity.

Definition in file CALHEL3.f.

Function/Subroutine Documentation

calhel3()

subroutine calhel3	(	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(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), intent(out)	heli
	)

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.
[out]	UST	Estimated U Component (m/s) Of Storm motion.
[out]	VST	Estimated V Component (m/s) Of Storm motion.
[out]	HELI	Storm-relative heliciry (m**2/s**2).

Note

• CANGLE Critical angle.
• 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
2021-03-15	E Colon	CALHEL2 modified to compute effective rather than fixed layer helicity
2021-09-02	Bo Cui	Decompose UPP in X direction
2022-05-12	E Colon	Resolved a bug which looped over the calculation of SRH at two fixed levels, erroneously doubling the magnitude.

Author

Michael Baldwin W/NP2

Date

1994-08-22

Definition at line 49 of file CALHEL3.f.

References exch().

Referenced by miscln().