eps and nscan in poisson_grid_fill

From: Jiaxin Zhang <jiaxinzhang3_at_nyahnyahspammersnyahnyah>
Date: Fri Aug 23 2013 - 21:49:35 MDT

Dear NCL users,

I am using the function “poisson_grid_fill” for the first time and I have
some questions about the arguments of that function. I guess that this
function is only going to fill values in the grids with missing values,
without modifying those grids with already existant values, right?

Apparently, the “poisson_grid_fill” works very well with my data using the
same default values for the arguments provided in example 1 in the web (see
attached code for temperature).

My questions are:

- It seems that the argument eps is variable dependent according to the
web. Do you think I can use the same eps value (for instance 1.e-2) for all
my climate variables (temperature, rain, ...)? Or maybe is it necessary to
modify this depending on the approximate ranges of values for the climate
variables? I have included information about the ranges of my climate
variables for 1 year at the end of the message in case this may help. Also,
because I have climate values for different years, I guess I could use the
same eps values for different years.

- I have tried nscan=1500, and it takes some time to complete the grid
filling for a netcdf with 2920 times. Do you think that when using a lower
value than 1500 for nscan it is going to be quicker to complete this part?
Or if it nscan is too low, perhaps then the results are not very reliable?
What are your suggestions?

Could anyone please have a look at the obtained plot with filled values for
temperature from the script "test_grid_filling.ncl" and let me know your
opinion? Do I need to modify something in the script? I am not completely
sure about the most appropriate values for some of the arguments in the
function. Can I use the same argument values for all my climate variables?
With respect to the obtained results with this function, I am not
interested in the climate values located in water grids.

Thank you!



In case it helps, the ranges and means of climate values for 1 year in my
netcdf files are, temperature (min=210, mean=282, max=325); longwave
radiation (min=56, mean=298, max=478); shortwave radiation (min=0,
mean=177, max=1119); specific humidity (min=1e-5, mean=0.0069,
max=0.02969); rain (min=0, mean=2.32e-5, max=0.00565); pressure (min=56104,
mean=95094, max=106001); wind (min=2.05e-5, mean=2.87, max=25.46).

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Received on Fri Aug 23 21:49:51 2013

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