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***fonction sgamatd - pente de TD lors de VV non-sature
*

      function sgamatd(td, tt, ti, pr, typv, swph),1
*
#include "impnone.cdk"
*
      real sgamatd
      real td, tt, ti, pr
*
      integer typv
*
      logical swph
*
*author
*       N. Brunet (septembre 2000)
*
*object
*       to compute the TD lapse rate during an adiabatic
*       and unsaturated ascent
*       2 derivatives are offered: dtd/dp and dtd/dz; the choice is
*       controlled via "typv"
*     
*       dtd/dp is > 0 and in K/pa
*       dtd/dz is < 0 and in K/m
*
*arguments
*       td - dew point temperature (K)
*       tt - temperature (K)
*       ti - temperature (K) at which we start calculating
*            latent heat of sublimation
*            if swph=false, ti is n/a
*            ti must be .LE. trpl
*       pr  - pressure (pa)
*       typv - if = 1; compute dtd/dp
*                 = 2: compute dtd/dz
*       swph - if .true.: phase ice and water are considered
*                 .false.: phase water for all temperatures with
*                          computation of saturation
*implicites
#include "consphy.cdk"
*modules
      external inctphy, schal
*
**
*----------------------------------------------------------------
*
      real schal, latheat
*
#include "initcph.cdk"
*----------------------------------------------------------------
*
*      ---calcule chaleur latente
      latheat = schal(td, ti, swph)
*
      if(typv .eq. 1) sgamatd = (rgasd*(td**2))/(eps1*latheat*pr)
*
      if(typv .eq. 2) sgamatd = -grav*(td**2)/(eps1*latheat*tt)
*
      return
      end