SUBROUTINE PREPW(DRPTPS,DLONS,DLATS,DPRES,
     *  RTYPES,RSPRES,
     *  MWDAT,PSG,FACT,FACTOR,NLAT,NLON,NSIG,GLATS,GLONS,SIGL)
C$$$  SUBPROGRAM DOCUMENTATION BLOCK
C                .      .    .                                       .
C SUBPROGRAM:    PREPW       PRELIMINARY STUFF BEFORE RES. CALC. W
C   PRGMMR: PARRISH          ORG: W/NMC22    DATE: 90-10-11
C
C ABSTRACT: PRELIMINARY STUFF BEFORE RESIDUAL CALCULATION FOR WINDS
C
C PROGRAM HISTORY LOG:
C   90-10-11  PARRISH
C
C   INPUT ARGUMENT LIST:
C     DRPTPS   - OBS TYPE IN, OBS ERROR OUT (LN(PS) UNITS)
C     DLONS,DLATS - OBS LONGITUDES AND LATITUDES (RADIANS IN AND OUT)
C     DPRES    - PRES (MB*10+QM IN, GRID COORDS IN SIGMA OUT)
C     RTYPES   - PREPDA OBSERVATION TYPES
C     MWDAT    - NUMBER OF OBSERVATIONS
C     PSG      - MODEL GUESS LOG(PSFC), P IN CB
C     FACTOR   - ARRAY OF 10M WIND FACTORS
C     NLAT     - NUMBER OF GAUSSIAN LATS POLE TO POLE
C     NLON     - NUMBER OF LONGITUDES
C     NSIG     - NUMBER OF SIGMA LEVELS
C     GLATS,GLONS - GRID LATITUDES
C     SIGL     - SIGMA LAYER MIDPOINT VALUES
C
C   OUTPUT ARGUMENT LIST:
C     RSPRES   - OBSERVATION PRESSURES
C     FACT     - NEAR SURFACE REDUCTION IN WIND FACTOR AT OBS.
C     AND AS INDICATED ABOVE
C
C ATTRIBUTES:
C   LANGUAGE: CFT77
C   MACHINE:  CRAY YMP
C
C$$$
C--------
C
C-CRA          DIMENSION DRPTPS(MWDAT),DLONS(MWDAT),DLATS(MWDAT),DPRES(MWDAT)
C-CRA          DIMENSION PSG(NLAT+1,NLON+2)
C-CRA          DIMENSION GLATS(NLAT),GLONS(NLON),SIGL(NSIG)
C-CRA          DIMENSION RTYPES(MWDAT)
C-CRA          DIMENSION RSPRES(MWDAT),FACT(MWDAT)
C-CRA          DIMENSION RBPRES(MWDAT)
C-CRA          DIMENSION RLOW(MWDAT),RHGH(MWDAT)
C-CRA          DIMENSION SIGLL(NSIG+1)
 
C          DIMENSION DRPTPS(_MWDAT_),DLONS(_MWDAT_)
          DIMENSION DRPTPS(85000),DLONS(85000)
C          DIMENSION DLATS(_MWDAT_),DPRES(_MWDAT_)
          DIMENSION DLATS(85000),DPRES(85000)
          DIMENSION PSG(96+1,192+2)
          DIMENSION GLATS(96),GLONS(192),SIGL(28)
C          DIMENSION RTYPES(_MWDAT_)
          DIMENSION RTYPES(85000)
C          DIMENSION RSPRES(_MWDAT_),FACT(_MWDAT_)
          DIMENSION RSPRES(85000),FACT(85000)
C          DIMENSION RBPRES(_MWDAT_)
          DIMENSION RBPRES(85000)
C          DIMENSION RLOW(_MWDAT_),RHGH(_MWDAT_)
          DIMENSION RLOW(85000),RHGH(85000)
          DIMENSION SIGLL(28+1)
C-------
C-------- LOCAL SPACE
C--------
C--------
C-------- GET LOG(SIG)
C--------
      SIGLL(1)=0.
      DO 100 K=1,NSIG
      SIGLL(K+1)=LOG(SIGL(K))
 100  CONTINUE
C--------
C-------- CONVERT OBS LATS AND LONS TO GRID COORDINATES
C--------
      CALL GDCRDP(DLATS,MWDAT,GLATS,NLAT)
      CALL GDCRDP(DLONS,MWDAT,GLONS,NLON)
C-------
C-------- 3.  INTERPOLATE SURFACE PRESSURE
C--------
C-------- OBTAIN GUESS SURFACE PRESSURE AT OBS LOCATIONS
C--------
      CALL INTRP2(PSG,RBPRES,DLATS,DLONS,NLAT,NLON,MWDAT)
      CALL INTRP2(FACTOR,FACT,DLATS,DLONS,NLAT,NLON,MWDAT)
C--------
C-------- CONVERT OBS PRESSURE TO SIGMA, THEN GET GRID COORDINATES
C--------
C-CRA                RSPRES=10.*EXP(DPRES)
C       DIMENSION RSPRES(MWDAT),FACT(MWDAT)
          DO ITMP=1,MWDAT
          RSPRES(ITMP)=10.*EXP(DPRES(ITMP))
          ENDDO
C-CRA                DPRES=DPRES-RBPRES
C       DIMENSION DRPTPS(MWDAT),DLONS(MWDAT),DLATS(MWDAT),DPRES(MWDAT)
          DO ITMP=1,MWDAT
          DPRES(ITMP)=DPRES(ITMP)-RBPRES(ITMP)
          ENDDO
C--------
C-------- FOR SSMI WIND SPEEDS, SET VERT POS TO 10M
C--------
      ALOG20=ALOG(.9976)
      ALOG10=ALOG(.9988)
      DO 45 I=1,MWDAT
        IF(NINT(RTYPES(I)).EQ.280) DPRES(I)=ALOG20
        IF(NINT(RTYPES(I)).EQ.281) DPRES(I)=ALOG10
        IF(NINT(RTYPES(I)).EQ.282) DPRES(I)=ALOG20
        IF(NINT(RTYPES(I)).EQ.283) DPRES(I)=ALOG20
        IF(NINT(RTYPES(I)).EQ.284) DPRES(I)=ALOG10
        IF(NINT(RTYPES(I)).EQ.285) DPRES(I)=ALOG10
        IF(NINT(RTYPES(I)).EQ.286) DPRES(I)=ALOG10
45    CONTINUE
      DO 46 I=1,MWDAT
        IF(DPRES(I) .LT. ALOG10 .AND. DPRES(I) .GT. SIGLL(2))
     *    FACT(I)=(DPRES(I)-ALOG10+FACT(I)*(SIGLL(2)-
     *     DPRES(I)))/
     *     (SIGLL(2)-ALOG10)
        IF(DPRES(I) .LT. SIGLL(2))FACT(I)=1.
 46   CONTINUE
      CALL GDCRDN(DPRES,MWDAT,SIGLL,NSIG+1)
      NUMHGH=0
      NUMLOW=0
      HGH=-1.E9
      XLOW=-1.E9
      RSIG=NSIG
      DO 58 I=1,MWDAT
        RLOW(I)=MIN(DPRES(I),0.)
        DPRES(I)=DPRES(I)-1.
        RHGH(I)=MAX(DPRES(I)-.001-RSIG,0.)
        RHGH(I)=ABS(RHGH(I))
        RLOW(I)=ABS(RLOW(I))
        IF(RHGH(I).NE.0.) NUMHGH=NUMHGH+1
        IF(RLOW(I).NE.0.) NUMLOW=NUMLOW+1
        HGH=MAX(RHGH(I),HGH)
        XLOW=MAX(RLOW(I),XLOW)
58    CONTINUE
      WRITE(6,900)MWDAT,NUMHGH,NUMLOW,HGH,XLOW
900   FORMAT(' NUMBER OF WINDS=',I8,' NUMBER EXTRAPOLATED ABOVE',
     *   ' TOP SIGMA LAYER=',I8,/,'  NUMBER EXTRAPOLATED BELOW',
     *   ' BOTTOM SIGMA LAYER=',I8,/,' LARGEST EXTRAPOLATION',
     *   ' ABOVE=',F12.2,/,' LARGEST EXTRAPOLATION BELOW=',F12.2)
      DO 908 I=1,MWDAT
        DRPTPS(I)=1./(DRPTPS(I)
     *    +1.E6*RHGH(I)+4.*RLOW(I))**2
908   CONTINUE
      RETURN
      END