<html><head></head><body><div class="ydpce4cebadyahoo-style-wrap" style="font-family:bookman old style, new york, times, serif;font-size:16px;"><div dir="ltr" data-setdir="false"><div><div>Hi,</div><div>I faced something interesting which I didn’t know in NCL. It might be obvious for many of you, however, I would like to share it.</div><div>I tried to plot wind barb at 10m level above the ground from GFS0.25 data. First, I used following lines:</div><div><span style="white-space: pre-wrap;"> </span>u10 = fi->UGRD_P0_L103_GLL0({10},:,:)</div><div><span style="white-space: pre-wrap;"> </span>v10 = fi->VGRD_P0_L103_GLL0({10},:,:)</div><div><span style="white-space: pre-wrap;"> </span>u10 <span style="background-color: rgb(253, 248, 105);">:=</span> u10*1.94386<span style="white-space: pre-wrap;"> </span>; Turn wind into knots</div><div><span style="white-space: pre-wrap;"> </span>v10 := v10*1.94386</div><div><span style="white-space: pre-wrap;"> </span>u10@units = "kts"</div><div><span style="white-space: pre-wrap;"> </span>v10@units = "kts"</div><div>The resulted map was something like plt1 which is wrong.</div><div>Then I tried to use the following lines:</div><div><span style="white-space: pre-wrap;"> </span>u10 <span style="background-color: rgb(253, 248, 105);">=</span> u10*1.94386<span style="white-space: pre-wrap;"> </span>; Turn wind into knots</div><div><span style="white-space: pre-wrap;"> </span>v10 <span style="background-color: rgb(253, 248, 105);">=</span> v10*1.94386</div><div>This turn the resulted map (plt2) was correct.</div><div>I’ll be thankful if some one could explain me why using “:=” is false and using “=” is true in this situation.</div><div><br></div></div><br></div><div><br></div><div class="ydpce4cebadsignature"><div dir="ltr" style="font-family:old times, serif;font-size:16px;"><div><div dir="ltr" style="color:rgb(0, 0, 0);font-family:old times, serif;font-size:16px;"><i><font size="2">-----------------------------------------------------------------------------</font></i></div><div dir="ltr" style="color:rgb(0, 0, 0);font-family:old times, serif;font-size:16px;"><i><font size="2">Sincerely,</font></i></div><div dir="ltr" style="color:rgb(0, 0, 0);font-family:old times, serif;font-size:16px;"><i><font size="2">Ehsan Taghizadeh<br></font></i></div></div><br></div></div></div></body></html>