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North America landmass extractiong using Land_mask function in idl [message #91477] Fri, 17 July 2015 17:27
siumtesfai is currently offline  siumtesfai
Messages: 62
Registered: April 2013
Member
Hello All,

I have Climate model data with the following dimension

data = [144,73] ; longitude X latitude

I am interested in analyzing the landmass only. I would exclude ocean data.

I learned that there is idl function that does what I am interest to do.

That is land_mask.pro

However, here is my problem

land = land_mask (resolution=[2.5,2.5], lat=lat,lon=lon)

This would provide a dimension of

land = [ 144,72] :

0 represent ocean
1 represent land

I would do the following to get the landmass data which I know it has a dimension of 144 longitude by 73 latitude with 2.5 by 2.5 resolution

landmass= fltarr(144,73)
FOR i=0,143 do begin
FOR j=0,72 do begin

x=reform(land(i,j))

y=where(x GT 0 )

if y(0) GE 0 then begin

landmass(i,j)=data(i,j)

endif else begin

landmass(i,j)= !F.values_NAN

endelse

ENDFOR
ENDFOR

Problem is out of range latitude range that is the j loop


Additional example is below


land = LAND_MASK( lat=lat,lon=lon,Limit=[-170,30,-50,75],resolution=[2.5,2.5])


Land_mask function provide the following dimension for north america domain


land = [48,18]


It should have given the following dimension


land =[49,17]

What am i missing ?

Thank you very much for you help

Best regards
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