[gradsusr] Help: Extent

[Fernanda Casagrande]

Dear All,

I have a problem with the calculation of the area (million km2).

I have a file of sea ice (ice concentration data from 0-100%) and I need to create a time series with a total extension of sea ice in the arctic and antartica (million km2). For this calculation, usually consider only areas with ice concentration equal to or above 15%, so I used the function maskout.

The. gs is running but the values ​​for the Arctic are wrong, can someone help me? Some other method to calculate the area (million km2)

these data are from satellite.


'sdfopen X172.16.9.158.108.11.23.58.nc'

*calculate area (million km2)
'dx=2*3.1416*6371*cos(lat*3.1416/180)/360.0*cdiff(lon,x)/2 '
'dy=2*3.1416*6371/360.0*cdiff(lat,y)/2'
'area=(dx*dy)'  
'fracao=area*(icec/100)'


say 'calcula a area'

'set lon 0 360'
'set lat -90 90'
'set t 1 last'


'define ones = const(const(maskout(icec,icec-15),1),0,-u)' 
'set x 1'
'set y 1'


'define xx=tloop(asum(ones*area,lon=0,lon=360,lat=-90,lat=0))'
'd xx'

'ltrend xx a b c'
'set ccolor 2'
'd a';'d b'
trend=subwrd(result,4)
 say 'trend='trend

' d c'
rmse=subwrd(result,4)
 say 'rmse='rmse

'draw title Antarctic Sea Ice obs incl.'trend' rmse. 'rmse' '


regards





Fernanda 		 	   		  
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