请教下确定0度层高度如何跳出循环

ta383045387

gs如下，算法是通过0度层上下两个等压面位势高度和温度，线性插值求0度层高度，但是总也无法跳出while循环
'reinit'
'sdfopen e:\711\nc\hgt.1960.nc'
'sdfopen e:\711\nc\air.1960.nc'
'set grads off'
'set lon 112.87'
'set lat 35.5'
'set t 689 691'
n=1
while(n<17)
'set z 'n''
'define tt1=air.2-273.15'
'define zz1=hgt.1'
'set z 'n+1''
'define tt2=air.2-273.15'
'define zz2=hgt.1'
if(tt1>0&tt2<0)
break;endif
n=n+1
endwhile
'define zz=tt2*(zz2-zz1)/(tt1-tt2)+zz2'
'set gxout line'
'd zz'
'printim C:\Users\Lenovo\Desktop\gs\NCEP\hail\04062120\physics\high-0.png white'
'grads2ascii zz C:\Users\Lenovo\Desktop\gs\NCEP\hail\04062120\physics\high-01.txt %8.1f 1'

ta383045387

有木有老哥帮忙看下，感谢{:eb302:}

逆光--

请问楼主解决了吗？也想求零度层高度