From: Xin Xi <xxi_at_nyahnyahspammersnyahnyah>

Date: Mon Nov 11 2013 - 21:27:25 MST

Date: Mon Nov 11 2013 - 21:27:25 MST

Hello,

I have a 2D field X from WRF with coordinates lat2d and lon2d. I want to

calculate the sum of subset of X within lat/lon bounds of (min_lat,

max_lat) and (min_lon, max_lon). I tried two different ways, which I

expected the same results but they turn out to be different. Which is the

correct way?

method 1:

X=where(lat2d.lt.min_lat .or. lat2d.gt.max_lat .or. \

lon2d.lt.min_lon.or.lon2d.gt.max_lon, 0, X)

sum_X=sum(X)

(in fact, the original X is missing value outside the lat/lon bounds, I use

the where function just for precaution).

method 2:

opt=True

loc=wrf_user_ll_to_ij(geo_file,(/min_lon,max_lon/),(/min_lat,max_lat/),opt)

loc=loc-1

subsetX=X(loc(1,0):loc(1,1) , loc(0,0):loc(0,1))

sum_X=sum(subsetX)

The sum_X from method 2 is a lot smaller than method 1. Is it because

wrf_user_ll_to_ij loses some grids at the bounds?

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Received on Mon Nov 11 21:27:38 2013

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