Functions/Subroutines
subroutine	NGMSLP
	SUBPROGRAM: NGMSLP NMC SEA LEVEL PRESSURE REDUCTION PRGRMMR: TREADON ORG: W/NP2 DATE: 93-02-02. More...

Function/Subroutine Documentation

subroutine NGMSLP ( )

SUBPROGRAM: NGMSLP NMC SEA LEVEL PRESSURE REDUCTION PRGRMMR: TREADON ORG: W/NP2 DATE: 93-02-02.

ABSTRACT:

THIS ROUTINE COMPUTES SEA LEVEL PRESSURE USING THE
HYDROSTATIC EQUATION WITH THE SHUELL CORRECTION.  THE
FOLLOWING IS BASED ON DOCUMENTATION IN SUBROUTINE 
OUTHYDRO OF THE NGM:

THE FUNDAMENTAL HYDROSTATIC EQUATION IS
   D(HEIGHT)
   ---------  =  TAU = VIRTUAL TEMPERATURE * (RGAS/GRAVITY)
   D (Z)
 WHERE
   Z = MINUS LOG OF PRESSURE (-LN(P)).

SEA-LEVEL PRESSURE IS COMPUTED FROM THE FORMULA
   PRESS(MSL) = PRESS(GROUND) * EXP( F)
WHERE
   F        = HEIGHT OF GROUND / MEAN TAU
   MEAN TAU = ( TAU(GRND) + TAU(SL) ) / 2

IN THE NGM TAU(GRND) AND TAU(SL) ARE FIRST SET USING A 
6.5DEG/KM LAPSE RATE FROM LOWEST MDL LEVEL.  THIS IS MODIFIED
BY A CORRECTION BASED ON THE CRITICAL TAU OF THE SHUELL
CORRECTION:
             TAUCR=(RGASD/GRAVITY) * 290.66

1) WHERE ONLY TAU(SL) EXCEEDS TAUCR, CHANGE TAU(SL) TO TAUCR.

2) WHERE BOTH TAU(SL) AND TAU(GRND) EXCEED TAUCR,
   CHANGE TAU(SL) TO TAUCR-CONST*(TAU(GRND)-TAUCR  )**2
   WHERE CONST = .005 (GRAVITY/RGASD)

THE AVERAGE OF TAU(SL) AND TAU(GRND) IS THEN USED TOGETHER
WITH THE GROUND HEIGHT AND PRESSURE TO DERIVE THE PRESSURE
AT SEA LEVEL. 

HEIGHT OF THE 1000MB SURFACE IS COMPUTED FROM THE MSL PRESSURE
FIELD USING THE FORMULA:

  P(MSL) - P(1000MB) = MEAN DENSITY * GRAVITY * HGT(1000MBS)

WHERE P(MSL) IS THE SEA LEVEL PRESSURE FIELD WE HAVE JUST
COMPUTED.


MEB 6/13/02: THIS CODE HAS BEEN SIMPLIFIED CONSIDERABLY FROM
THE ONE USED IN ETAPOST.  HORIZONTAL SMOOTHING HAS BEEN
REMOVED AND THE FIRST MODEL LEVEL IS USED RATHER
THAN THE MEAN OF THE VIRTUAL TEMPERATURES IN
THE LOWEST 30MB ABOVE GROUND TO COMPUTE TAU(GRND).

PROGRAM HISTORY LOG: 93-02-02 RUSS TREADON 98-06-08 T BLACK - CONVERSION FROM 1-D TO 2-D 00-01-04 JIM TUCCILLO - MPI VERSION 01-10-25 H CHUANG - MODIFIED TO PROCESS HYBRID MODEL OUTPUT 01-11-02 H CHUANG - MODIFIED LINE 234 FOR COMPUTATION OF SIGMA/HYBRID SLP 01-12-18 H CHUANG - INCLUDED SMOOTHING ALONG BOUNDARIES TO BE CONSISTENT WITH MESINGER SLP 02-06-13 MIKE BALDWIN - WRF VERSION 06-12-18 H CHUANG - BUG FIX TO CORRECT TAU AT SFC

USAGE: CALL NGMSLP INPUT ARGUMENT LIST: NONE

OUTPUT ARGUMENT LIST: NONE

OUTPUT FILES: NONE

SUBPROGRAMS CALLED: UTILITIES: NONE LIBRARY: COMMON - CTLBLK

ATTRIBUTES: LANGUAGE: FORTRAN MACHINE : CRAY C-90

Definition at line 89 of file NGMSLP.f.

Functions/Subroutines

Function/Subroutine Documentation