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slalib/atmt.f

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+      SUBROUTINE sla__ATMT (R0, T0, ALPHA, GAMM2, DELM2,
+     :                      C1, C2, C3, C4, C5, C6, R, T, DN, RDNDR)
+*+
+*     - - - - -
+*      A T M T
+*     - - - - -
+*
+*  Internal routine used by REFRO
+*
+*  Refractive index and derivative with respect to height for the
+*  troposphere.
+*
+*  Given:
+*    R0      d    height of observer from centre of the Earth (metre)
+*    T0      d    temperature at the observer (K)
+*    ALPHA   d    alpha          )
+*    GAMM2   d    gamma minus 2  ) see HMNAO paper
+*    DELM2   d    delta minus 2  )
+*    C1      d    useful term  )
+*    C2      d    useful term  )
+*    C3      d    useful term  ) see source
+*    C4      d    useful term  ) of sla_REFRO
+*    C5      d    useful term  )
+*    C6      d    useful term  )
+*    R       d    current distance from the centre of the Earth (metre)
+*
+*  Returned:
+*    T       d    temperature at R (K)
+*    DN      d    refractive index at R
+*    RDNDR   d    R * rate the refractive index is changing at R
+*
+*  Note that in the optical case C5 and C6 are zero.
+*
+*  Last revision:   26 December 2004
+*
+*  Copyright P.T.Wallace.  All rights reserved.
+*
+*  License:
+*    This program is free software; you can redistribute it and/or modify
+*    it under the terms of the GNU General Public License as published by
+*    the Free Software Foundation; either version 2 of the License, or
+*    (at your option) any later version.
+*
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU General Public License for more details.
+*
+*    You should have received a copy of the GNU General Public License
+*    along with this program (see SLA_CONDITIONS); if not, write to the 
+*    Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
+*    Boston, MA  02111-1307  USA
+*
+*-
+
+      IMPLICIT NONE
+
+      DOUBLE PRECISION R0,T0,ALPHA,GAMM2,DELM2,C1,C2,C3,C4,C5,C6,
+     :                 R,T,DN,RDNDR
+
+      DOUBLE PRECISION TT0,TT0GM2,TT0DM2
+
+
+      T = MAX(MIN(T0-ALPHA*(R-R0),320D0),100D0)
+      TT0 = T/T0
+      TT0GM2 = TT0**GAMM2
+      TT0DM2 = TT0**DELM2
+      DN = 1D0+(C1*TT0GM2-(C2-C5/T)*TT0DM2)*TT0
+      RDNDR = R*(-C3*TT0GM2+(C4-C6/TT0)*TT0DM2)
+
+      END