<div dir="ltr"><div class="gmail_quote"><br><br><br><div dir="ltr">Dear All:<div> I met a problem when I try to caculate the velocity potential according to function:uv2sfvpf.</div><div> The u wind and v wind used in the study is the NCEP/NCAR reanalysis I monthly dataset, The 1000 hPa wind in 1948:1:1:0 is shown in Fiugre 1, and the corresponding stream function and velocity potential is shown in Figure 2 and 3.</div><div> It is shown that in Figure 1, there is an anticyclone around the Northwestern Pacific(marked as A in red), and the wind over Tibetan Plateau (marked as B in purple) is significantly divergence.</div><div> Figure 2 shows the stream function calculated by the u and v wind in Figure 1. The positive and negative of stream function is in accordance with the cyclonic/anticyclonic center in Figure 1.</div><div> However, the sign of velocity potential is incorrect( Figure 3). The wind over Tibetan Plateau is significantly divergence(Figure 1, mark B) ,but the velocity potential over Tibetan Plateau(Figure 3, mark C) is negative ,which indicates the convergence circulation over this region.</div><div> The result of velocity potential confused me ,and I can't find if there are mistakes in my ncl program. Looking forward to your kindly help.</div><div> The ncl program is shown as follows:</div><div><br></div><div>begin<br></div><div><div> f10<span style="white-space:pre-wrap"> </span>= addfile("<a href="http://uwnd.mon.mean.nc" target="_blank">uwnd.mon.mean.nc</a>","r")</div><div><br></div><div><span style="white-space:pre-wrap"> </span>uwnd = f10->uwnd(0:792,0:11,::-1,:) ; latitude of NCEP reanalysis is 90:-90, so I reversed the latitude to meet the request of function: uv2sfvpf</div><div><span style="white-space:pre-wrap"> </span></div><div><span style="white-space:pre-wrap"> </span>print(uwnd&lat)</div><div><span style="white-space:pre-wrap"> </span></div><div><span style="white-space:pre-wrap"> </span>f20<span style="white-space:pre-wrap"> </span>= addfile("<a href="http://vwnd.mon.mean.nc" target="_blank">vwnd.mon.mean.nc</a>","r")</div><div><span style="white-space:pre-wrap"> </span></div><div><span style="white-space:pre-wrap"> </span>vwnd = f20->vwnd(0:792,0:11,::-1,:)</div><div><br></div><div><span style="white-space:pre-wrap"> </span></div><div><span style="white-space:pre-wrap"> </span>sf<span style="white-space:pre-wrap"> </span>=<span style="white-space:pre-wrap"> </span>new((/dimsizes(uwnd)/),float,uwnd@_FillValue)</div><div><span style="white-space:pre-wrap"> </span>vp<span style="white-space:pre-wrap"> </span>=<span style="white-space:pre-wrap"> </span>new((/dimsizes(uwnd)/),float,uwnd@_FillValue)</div><div><br></div><div><span style="white-space:pre-wrap"> </span>copy_VarCoords(uwnd,sf)</div><div><span style="white-space:pre-wrap"> </span>copy_VarCoords(uwnd,vp)</div><div><span style="white-space:pre-wrap"> </span>uv2sfvpf(uwnd,vwnd,sf,vp)</div></div><div><div> system("rm -f "+"<a href="http://sf.nc" target="_blank">sf.nc</a>")</div><div><span style="white-space:pre-wrap"> </span>f70=addfile("<a href="http://sf.nc" target="_blank">sf.nc</a>","c")</div><div><span style="white-space:pre-wrap"> </span>f70->sf=sf</div><div> system("rm -f "+"<a href="http://vp.nc" target="_blank">vp.nc</a>")</div><div> f80=addfile("<a href="http://vp.nc" target="_blank">vp.nc</a>","c")</div><div><span style="white-space:pre-wrap"> </span>f80->vp=vp</div></div><div>end<br></div><div><br></div><div><br></div><div><br></div><div><img src="cid:ii_153a96db39ec6fd6" alt="内嵌图片 1" width="544" height="364"><br></div><div>Figure 1. NCEP/NCAR reanalysis wind of 1000 hPa in 1948:1:1:0</div><div><img src="cid:ii_153a977f962382a2" alt="内嵌图片 2" width="544" height="333"><br></div><div>Figure 2. Stream Function obtained by function:uv2sfvpf, using the wind in Figure 1(1948:1:1:0).</div><div><img src="cid:ii_153a97ab14b656bf" alt="内嵌图片 3" width="544" height="330"><br></div><div>Figure 3. Velocity Potential obtained by function:uv2sfvpf, using the wind in Figure 1(1948:1:1:0).<br></div><div><br></div></div>
</div><br></div>