'reinit'
'sdfopen air.2000.nc'
'sdfopen hgt.2000.nc'

'set lev 500'
'set t 1 100'

'R=6.37e6'
'D2R=(3.1415/180)'
'g=9.81'

'dx=cdiff(lon,x)*R*D2R*cos(lat*D2r)'
'dy=cdiff(lat,y)*R*D2R'

'dtx=cdiff(air,x)'
'dty=cdiff(air,y)'

'geo=hgt.2*g'
'dgx=cdiff(geo,x)'
'dgy=cdiff(geo,y)'
'ggx=(dgx/dx)'
'ggy=(dgy/dy)'
'f=2*7.27e-5*sin(lat*D2R)'
'ug=(-1/f)*ggy'
'vg=(1/f)*ggx'

'TA=-1*(ug*(dtx/dx)+vg*(dty/dy))'

'set lon -10 90'
'set lat 10 80'