<div dir="ltr">Hi Gehne, and NCL users,<div><br></div><div style>Thanks for the hints, I knew this function, but I have following question prior of using the ezfft:</div><div style><br></div><div style>1. How can I convert the vertical level in my data (which is in pressure) to altitude (geometry) in order to get the vertical wavenumber with units km? I dont have any idea for this using ncl.</div><div style><br></div><div style>2. do I need to interpolat the vertical level (km) to equally space (per 1 km each) ?</div><div style><br></div><div style>3. Is there any function or hints that you may purpose if I want to get the spectrum as a function as vertical wavenumber and frequency ?</div><div style><br></div><div style>Thank you for your experience and hints.</div><div style><br></div><div style>Dr. Chang.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Feb 17, 2015 at 5:08 PM, Maria Gehne - NOAA Affiliate <span dir="ltr"><<a href="mailto:maria.gehne@noaa.gov" target="_blank">maria.gehne@noaa.gov</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Chang,<div><br></div><div>the function ezfftf should do that. </div><div><br></div><div><a href="https://www.ncl.ucar.edu/Document/Functions/Built-in/ezfftf.shtml" target="_blank">https://www.ncl.ucar.edu/Document/Functions/Built-in/ezfftf.shtml</a><br></div><div><br></div><div>It works for multidimensional arrays as well as one dimensional arrays, for more than one dimension you need to reorder so that the pressure levels are the right most dimension. So if x = (time,lev,lat,lon) you may need to transform y = x(time,lat,lon,lev).</div><div><br></div><div>As with all FFT applications you probably need to taper the values you are trying to transform so that the end points are zero and you are essentially transforming a periodic sequence.</div><div><br></div><div>Hope this helps,</div><div><br></div><div>Maria</div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Sun, Feb 15, 2015 at 3:35 PM, Xi Chang <span dir="ltr"><<a href="mailto:xi.chang01@gmail.com" target="_blank">xi.chang01@gmail.com</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="ltr">Hallo NCL,<div><br></div><div>is there any trick or function in ncl to decompose the data in pressure level to vertical wavenumber (m) based on FFT filter?</div><div><br></div><div>Thank you</div><span><font color="#888888"><div>Chang</div></font></span></div>
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