the following exponentail functions are set as an example:

fs(za)= istr*(1.-exp(-za/SD)) +(1-istr)*za
fsi(zt)=-istr*SD*alog(1.-istr*zt/zb*fs(zb))+(1-istr)*zt
fsk(zk)=zb/fs(zb)*fs(zk)

Functions these are further used to set specific transformation mtrix (gmus) and stretched vertical coordinate (zstr) defined in subroutine metryc

      gmus(k)=(SS-z(k))/SD*istr+float(1-istr)
      zstr(k)=fsi(z(k))

      data zstr
     ./0.00000,20.0000,48.4400,87.3300,137.230,197.670,267.550,
     . 350.950,448.820,561.520,689.530,833.440,993.840,1170.90,
     . 1364.68,1575.57,1803.89,2049.75,2312.95,2593.71,2892.23,
     . 3208.52,3542.15,3893.26,4261.91,4647.96,5050.84,5468.04,
     . 5896.41,6332.38,6771.96,7210.55,7647.52,8082.55,8515.59,
     . 8946.58,9375.43,9802.09,10226.5,10648.5,11068.2,11485.4,
     . 11900.0,12312.0,12721.4,13133.5,13551.5,13981.1,14428.0,
     . 14897.9,15396.5,15930.6,16507.8,17135.6,17821.9,18574.0,
     . 19399.9,20307.4,21304.0,22395.9,23588.5/ 

        zvert(1)=zstr(1)
        do k=2,l
	zvert(k)=.5*(zstr(k)+zstr(k-1))
        enddo  
        do  k=1,l-1
        gmus(k)=dz/(zvert(k+1)-zvert(k))
        enddo
        gmus(l)=dz/(zvert(l)-zvert(l-1))