Re: [ferret_users] Find Argo profiles within user-defined lat-long grid box

[Ansley Manke <a.c.manke@xxxxxxxxx>]

Hi Akash,

This FAQ that talks about Argo profile data, and which discusses the operations that  argo_zt.jnl does: https://ferret.pmel.noaa.gov/Ferret/faq/how-can-i-work-with-argo-float-profile-data

It opens the Argo data so that the profile data is in Z and T, with Z in the vertical direction (depth or pressure) and T the number of profiles.

When your dataset is open, there will be some variables representing longitude and latitude, in the T direction.  You can use these to define a mask, which would look like this. List the longitudes and latitudes, and the mask, to check what it does

   yes? let mask_lon_lat = if longitude gt 50 and longitude lt 78 and latitude gt 17 and latitude lt 25 then 1
   yes? list longitude, latitude, mask_lon_lat

Now you can apply the mask to a variable such as temp , or to a variable after which the argo_zt script has regridded to a pressure axis in Z.

   yes? let/like=temp masked_temp = mask_lon_lat * temp
   yes? let/like=temp masked_temp_on_pres = mask_lon_lat * temp_pn_pres

Another way to look at this kind of data is with PLOT/VS.  The first command below will show all of the temperature profiles. They will be upside-down. To reverse them, use /VLIM, with the maximum pressure from your dataset

   yes? plot/vs temp, pres
   yes? plot/vs/vlim=2000:0 temp, pres

You could do this with your masked data.

Finally, this kind of data, collections of profiles, is one kind of a DSG (Discrete Sampling Geometry) dataset.  The form of the ARGO files does not conform to the "ragged array" Discrete Sampling Geometry Data format that is implemented for automatic handling in PyFerret and Ferret.  I found an example dataset at https://www.nodc.noaa.gov/argo/ and when opening it in PyFerret I see a message saying it has a FeatureType attribute but cannot be opened as a DSG ragged array, and is initialized as a non-DSG dataset.  This is fine, it is just an informational note.

Ansley

On 9/13/2022 1:58 AM, Akash. S wrote:

Dear Ferret users,

I had a small question on Argo profile extraction on a desired grid box.

I am using "argo_zt.jnl" to plot the Argo profiles. The script uses all the locations from the input Argo data and gives profile output. But I need to extract the profiles only within a grid box (say, x=50:78/y=17:25). My data contain values beyond the desired grid box and I want to exclude them. Obviously the "set reg/x=50:78/y=17:25" will not work on this kind of data.

Is anyone done this kind of operation before? Can anyone give me a solution to this?

Thanks and regards,

Akash