<div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif">to follow up with an important detail here. <br></div><div class="gmail_default" style="font-family:verdana,sans-serif"><div dir="ltr" style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px"><br></div><div dir="ltr" style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px">Average: <br>(a) 0-6 and multiply by the area<br>(b) 0-4, and multiply by the area<br>(c) subtract: (a) -(b) then divide by ( area a - area b )</div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px">e.g. ignoring the fact that the earth is a sphere </div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px"><br></div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px">outer = dim_avg_n( masked0_6_array, (/0,1/) ) * (pi*6^2) ; some array where we've already masked the data we want, or subset the area we want</div><div dir="ltr" style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px">inner = dim_avg_n( masked0_4_array, (/0,1/) ) * (pi*4^2)<br></div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px">annulus = ( outer - inner ) / ( (pi*6^2) - (pi*4^2) )</div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px"><br></div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px">You can cancel all the pi's above for simplicity if desired. . </div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px"><br></div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px">==============================</div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px"><br></div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px">To do this with circles rather than squares however you could also use the layout from the Katrina circle script on the below page and add an extra gc_inout() to mask the inner 0 to x km circle. </div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px">Then you don't need to worry about areas so much. (Should probably still weight by the latitude though) </div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px"><a href="https://www.ncl.ucar.edu/Applications/latlon_subset.shtml" target="_blank">https://www.ncl.ucar.edu/<wbr>Applications/latlon_subset.<wbr>shtml</a></div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px"><br></div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px"><br></div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px"><br></div><div style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:12.800000190734863px"><br></div><div><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jan 29, 2018 at 10:31 PM, Dennis Shea via ncl-talk <span dir="ltr"><<a href="mailto:ncl-talk@ucar.edu" target="_blank">ncl-talk@ucar.edu</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">Average: <br>(a) 0-6 <br>(b) 0-4, <br>(c) subtract: (a)-(b)<br></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Mon, Jan 29, 2018 at 11:23 AM, Prashanth Bhalachandran via ncl-talk <span dir="ltr"><<a href="mailto:ncl-talk@ucar.edu" target="_blank">ncl-talk@ucar.edu</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 link="blue" vlink="#954F72" lang="EN-US"><div class="m_8131482382059315766m_2937415845448223556WordSection1"><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Bell MT",serif">Dear NCL’ers,<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Bell MT",serif">I have a question regarding the computation of winds in an annulus. <u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Bell MT",serif"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Bell MT",serif">That is, say I have a center lat and lon : cenlat, cenlon <u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Bell MT",serif">limit = 2 ; In degrees <u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Bell MT",serif"> b1 = cenlat-limit<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Bell MT",serif"> b2 = cenlat+limit<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Bell MT",serif"> b3 = cenlon-limit<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Bell MT",serif"> b4 = cenlon+limit<u></u><u></u></span></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Bell MT",serif">This is what I use if want to average the winds in a box that <b>is 2 degrees on either side of the center</b> (4 degree x 4degree n total). <u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Cambria Math",serif">uav = dim_avg_n(dim_avg_n(uu(tcount,<wbr>:,{b1:b2},{b3:b4}),2),1)<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Cambria Math",serif"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Cambria Math",serif">However, what I am now interested in is averaging around an <b>annulus</b> (say between 4 degrees to 6 degrees from the center of the hurricane). What is the best way to do that? <u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Cambria Math",serif"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Cambria Math",serif">Thank you, <u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Cambria Math",serif">Prashanth <u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:14.0pt;font-family:"Cambria Math",serif"><u></u> <u></u></span></p></div></div><br></div></div>______________________________<wbr>_________________<br>
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