grads 中读写数据fwrite

'reinit'
'sdfopen d:/gfdl21/va_A2.19960101-20001231.nc'
'set fwrite F:/homework/synoptic/model/vwnd/v1996.dat'
*'set lat -30 30'
*'set lon 119.5 288.5'
'set x 1 144'
'set y 1 90'
tt=1
yr=0
while(tt<=1825)
'set t 'tt
*---------------
if(math_fmod(tt,365)=1)
yr=yr+1
'disable fwrite'
'set fwrite F:/homework/synoptic/model/vwnd/v'1995+yr'.dat'
endif
*------------------------
'set lev 20000'
'set gxout fwrite'
'd va'
tt=tt+1
endwhile
'disable fwrite'
'reinit'