I'm currently interested in using site-specific data to describe the atmospheric conditions above a volcano of interest. I was able to follow the VHub instructions and download Geopotential, UWind, and VWind data in NetCDF form from the NOAA PSD site. However, I'm having trouble building the NetCDF libraries to extract the data, as I'm rather computer illiterate, and the UCAR Unidata site is a bit too erudite for me to comprehend. Is there anyone familiar with the ncdump utility who can give me an introductory-level list of build steps? I have both Mac and Windows machines, so instructions for both would be fantastic, if at all possible. Cheers!
I seem to have been able to answer my own question (at least partially). I was finally able to navigate to this page on the Unidata site:
http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-install/Getting-Prebuilt-DLL.html#Getting-Prebuilt-DLL
From there, I downloaded the .zip, and extracted it to a local directory. Then, to use ncdump.exe, I opened Command Prompt and changed the directory to reflect the folder in which I put the NetCDF utilities, and entered "\dir>ncdump" and my commands. Note that this was on a Windows machine; instructions may vary if on a different OS.
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However, I am still stuck when trying to running a Perl script from the Command Prompt; I seem to be lacking the Math/Trig.pm module because it throws the error "Can't find Math/Trig.pm in @INC". I have downloaded the Math::Complex module (which includes Math::Trig), but I'm not clear on how to get Perl to find it in the directory where it's saved. Any ideas? Many thanks in advance!
David Pierce has also written an R package called "ncdf4" that can read netCDF files. Below is an example use, for an oceanographic dataset (sea-surface temperature, annually averaged). (Unfortunately, RG won't let me format this as code, so I double spaced it. The quote marks will probably come out wrong and have to be fixed if you copy/paste to start working with your own data.)
library(ncdf4)
con
There are plenty of options to read NetCDF files. However, if you want to change the format data, you'll have to use something that let you process NetCDF format data and write it in your format. Since you are using windows I would think that Matlab or Igor could solve your problem. If you only want to visualize the data a java-based program like panoply could be helpful for you (should work for Mac too). Otherwise, in a Mac you need to install something like cdo or nco that help you process NetCDF data in command line using a UNIX console or the NCAR Command Language (NCL) through its binaries.
It depends what you want to do with the data once you get it out of the netcdf files. Using IDL, MatLab, R or something similar would allow you read it in (a quick look at the help menu for any of those software packages would give you the commands and syntax to use), and then you could write it out as a text file if that's easier for you to work with. A text file will probably be a lot bigger than the netcdf file though so if you're looking at using a large volume of data then you might be better keeping it in netcdf and extracting whatever you need from it directly (or do the rest of the processing within the same softare package so you don't need to create another file). The netcdf command-line tools are pretty good for interrogating the file - if you redirect the output you can create textfiles for reference from these too (if you use the command line tools on your mac then redirect the output using something like >. For example: ncdump -h mynetcdffile.nc > headers.txt will create a textfile called headers.txt containing the headers from the mynetcdffile.nc.
Hi all,
Cheers for all the assistance! I admit that some of the suggestions posed here are a bit out of my league (e.g. I've never used R, or MATLAB), but again, thank you nonetheless. Moreover, thanks for your patience (and apologies) as this question continues to metamorphose.
A quick update about Mac OS: this site proved remarkably helpful in getting me set up for netCDF on Mac (my preferred OS), so if anyone needed any refreshers on the installation etc., I suggest giving that a read. (Additionally, note you do have to change the extensions on the TEPHRA2 .conf files to use them in Perl on Mac.)
Sebastien, it seems you might be best able to help me. Looking at the dWind page, it seems the program generates what I already have, using the various scripts available for download with TEPHRA2: 3-column text files with altitude, wind speed, and wind direction. The problem is, each of these wind files represents a discrete day; I downloaded 6 years of wind data as this is representative of the duration of the eruption I'm examining. Is there someway to average all of these files together to get an average wind field that can be used in TEPHRA2? (I seem unable to load multiple wind files for the tool to use as it advances to each time step.) That, or if I use dWind, will I be able to generate an average file for the timeframe I specify?
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Another TEPHRA2 question: I tried running the model using the wind just from an arbitrary day. While the model ran successfully, I was not able to generate any plots presumably because I only provided the model with the location of the vent itself; this being a point, it was unable to generate any mass per area calculations and thus failed to render an isopach map. I understand I can import a grid file (e.g. DEM) to give the tool a defined area and topography, but what filetype can (or must) I use as a grid file?
With many thanks in advance,
James
http://mazamascience.com/WorkingWithData/?p=1474
Hi Sebastien, I downloaded your tool, however i am unable to enter any values for the longitude parameter. Is this a bug?
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