grads环境风切变，区域求平均值

夏天温暖

'reinit'
'enable print d:\zh\850-200uaa.gmf'
'open d:\zh\fnl_20151003_00_00.ctl'
'set grid off'
'set grads off'
'set mpdset hires'
'set clab forced'
'set lon 96 126'
'set lat 10 30'
'set t 1'
'define a1=UGRDprs(lev=850)-UGRDprs(lev=200)'
'd aave(a1,lon=105.5,,lat=8.5,lon=125.5,lat=28.5)'
'set  gxout line'
'set ccolor 4'
'set cthick 6'

'draw title 200-850aa'

'print'
'c'
'disable print'
'reinit'

river

先去看grads的基础知识