[ferret_users] variance up to a time-varying level

["Gustafson, William I" <william.gustafson@xxxxxxx>]

Title: variance up to a time-varying level

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Hello Ferreters,

I am running into a wall and would like to know if anybody has some suggestions on how to get around it. I have a 4-D (XYZT) dataset of clouds and wind (WRF output). For each time, I want to get the variance of w within the XYZ box defined by the full XY domain and up to the highest level in the domain containing a cloud. I have come up with an algorithm that works at one time, but it fails  when applied to a multi-time dataset because I have to evaluate an expression to a scalar to get it into the k=1:`lev`@var command. If anybody can get around this problem, I would be grateful for your assistance.

Here is what I am doing right now...

let cloudthresh = 0.00001
let cloudmixr = qcloud+qice
let event_mask = cloudmixr[k=@evnt:`cloudthresh`]   !Counts number of cloudy cells from the bottom of the domain
let event_max = event_mask[k=@max]   !At each column, find out how many cloudy cells exist
let event_max_mask = if event_mask eq event_max then 1   !Make a mask that goes to 1 at the top of the clouds for each col.
let cloud_top_lev3d = event_max_mask[k=@loc:1]    !The level of the highest cloud top within each column
let cloud_top_lev = cloud_top_lev3d[i=@max,j=@max]  !The single highest cloud top level in the domain
let w_var = w[i=1:`w,return=iend`@var,j=1:`w,return=jend`@var,k=1:`cloud_top_lev`@var]   !Variance of w up to cloud_top_lev

The last line is what fails when I do not set the time region to a single time.

Thanks,
    Bill

--------------------------------------------------------------------
William I. Gustafson Jr.
Atmospheric Science and Global Change Division
Pacific Northwest National Laboratory
3200 Q Ave., MSIN K9-30
Richland, WA 99352
(509)372-6110