如何更改气压

WOT

这是我在论坛里找到的别人的脚本，这个脚本绘制的是300hpa的水汽通量和散度，想问一下，我要绘制850hpa的水汽通量和散度要怎么更改脚本呢？'reinit'
'sdfopen F:\grads_vapor_flux1\uwnd.mon.mean.nc'
'sdfopen F:\grads_vapor_flux1\vwnd.mon.mean.nc'
'sdfopen F:\grads_vapor_flux1\shum.mon.mean.nc'
'set parea 1.5 10.0 1.5 8.0'
'set map 1 1 3'
'set mpdset cnworld cnriver'
'set lev 850'
'set xlopts 1 3 0.2'
'set ylopts 1 3 0.2'
'set xlint 10'
'set ylint 10'
'set t 161 804'
'define qu5=uwnd*shum.3/9.8'
'define qv5=vwnd.2*shum.3/9.8'
'set t 161'
'define qud5=ave(qu5,t+0,t=804,12)'
'define qvd5=ave(qv5,t+0,t=804,12)'
'define qdiv5=hdivg(qud5,qvd5)'

'set t 162 804'
'define qu6=uwnd*shum.3/9.8'
'define qv6=vwnd.2*shum.3/9.8'
'set t 162'
'define qud6=ave(qu6,t+0,t=804,12)'
'define qvd6=ave(qv6,t+0,t=804,12)'
'define qdiv6=hdivg(qud6,qvd6)'

'set t 163 804'
'define qu7=uwnd*shum.3/9.8'
'define qv7=vwnd.2*shum.3/9.8'
'set t 163'
'define qud7=ave(qu7,t+0,t=804,12)'
'define qvd7=ave(qv7,t+0,t=804,12)'
'define qdiv7=hdivg(qud7,qvd7)'

'set t 164 804'
'define qu8=uwnd*shum.3/9.8'
'define qv8=vwnd.2*shum.3/9.8'
'set t 164'
'define qud8=ave(qu8,t+0,t=804,12)'
'define qvd8=ave(qv8,t+0,t=804,12)'
'define qdiv8=hdivg(qud8,qvd8)'

'set t 165 804'
'define qu9=uwnd*shum.3/9.8'
'define qv9=vwnd.2*shum.3/9.8'
'set t 165'
'define qud9=ave(qu9,t+0,t=804,12)'
'define qvd9=ave(qv9,t+0,t=804,12)'
'define qdiv9=hdivg(qud9,qvd9)'

'define qud=(qud5+qud6+qud7+qud8+qud9)/5'
'define qvd=(qvd5+qvd6+qvd7+qvd8+qvd9)/5'
'define qdiv=(qdiv5+qdiv6+qdiv7+qdiv8+qdiv9)/5'
'set cmin -9e-6'
'set lon 60 150'
'set lat 0 60'

'set gxout shaded'
'd qdiv'
'set gxout barb'
'set ccolor 2'
'set gxout vector'
'd qud;qvd'
'cbarn 1.2 0'

'draw title 300hpa vapor flux and divergence'

'printim F:\grads_vapor_flux1\300.png white x2000 y1800'
'disable print'

二爷名声在外

虽然我不懂grads，但是我看到了'set lev 850'