Hi all,
Here are some related resources:
The @AVE transformation. Note that the @WGT transformation returns the weights used by the equivalent @AVE
transform.
A section on General Information on transformations.
FAQ on averages computed on the surface of the earth
Here's a Users List archive message about calculating the area of grid cells on the Earth's surface - which
is a technique that works in general - it's equivalent to @WGT in fact.
http://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2004/msg00026.html
Ansley
On 3/23/2017 10:12 PM, Abhishek Savita wrote:
Hi... all
I have also faced same problem earlier. I have checked it analytically as well as with the
matlab also. Actully ferret gives the weighted average if we give like var[x=@ave,y=@ave,z=@ave,.....].
But If anybody interested to compute normal average then in place of giving X, Y etc we should give
corresponding index number as var[i=@ave,j=@ave,.....]. Where i and j are the index number
corresponding Lon and lat.
Please check it I hope it will work.
with regards
Abhishek
On Fri, Mar 24, 2017 at 9:55 AM, Ryo Furue <furue@xxxxxxxxxx> wrote:
Hi Robert and Martin,
yes? list/k=1 temp[x=@ave,y=@ave]
...
-1.788
but I'd like to have area weighed averaged value. How should I told ferret that x and y is
long and lat for averaging computations,
With temp[x=@ave,y=@ave], Ferret does compute the area weighted average if the horizontal axes
are longitude and latitude. If the axes aren't longitude and latitude, Ferret computes x=@ave
and y=@ave separately (I think), which may not coincide with the correct area-weighted average.
I don't know if it's possible to compute the area of each gridbox within Ferret. You may have to
supply that information from outside. Then,
let area_temp = temp * boxarea
let area_average_temp = area_temp[x=@sum,y=@sum] / boxarea[x=@sum,y=@sum]
Ryo
--
Regards
Abhishek Savita
Research Scholar (Earth System Science Technology)
Center For Oceans, Rivers, Atmosphere & Land Science Technology
Indian Institute of Technology, Kharagpur
+91-8609704619