Contouring bug on lcc projection

还没有人认领这个 Issue。

This same issue is occurring for all data types. Quite often, though not always, one of any of the contoured data will spike sharply downward away from the rest of the contour (seen below in the yellow data). This happens quite often in the middle of the domain.
I doubt this is a problem with the data themselves or my analysis since this error makes the contour line cross other contour lines of the same data. If there were just an anomaly at the bottom of the domain, I would expect there to just be a gradient with the contouring toward it. This makes me think that the problem is all in the plotting.


Here's the plotting portion of my code.
`
#Plotting
fig = figure()
map = Basemap(llcrnrlon=-120.,llcrnrlat=20.,urcrnrlon=-50.,urcrnrlat=50.,\
rsphere=(6378137.00,6356752.3142),\
resolution='l',projection='lcc',\
lat_0=40.,lon_0=-98.,\
lat_1=30.,lat_2=60.)

#Draw geographical boundaries
map.drawcoastlines(color='red',linewidth=0.75)
map.drawstates(color='red',linewidth=0.75)
map.drawcountries(color='red',linewidth=0.75)
map.fillcontinents(color='black',lake_color='black')
map.drawmapboundary(fill_color='black')

#Create X-Y plane for contouring and filling on map
X,Y = map(asarray(longitude_grid), asarray(latitude_grid))

#1st Variable#
#------------#

levels = linspace(700., 1200., 126) #4 mb levels for SLP
cs = map.contour(X,Y,var,2,colors='c',linewidths=1.,levels=levels)
clabel(cs, fmt="%1.0f", fontsize=8, inline=1)

#2nd Variable#
#------------#

levels = linspace(0.,12000.,241) #50 m levels for thickness/height
cs = map.contour(X,Y,contr,2,colors='y',linewidths=0.75,levels=levels)
clabel(cs, fmt="%1.0f", fontsize=8, inline=1)

#Snow Contour#
#------------#

cs = map.contour(X,Y,snow,2,colors='w',linewidths=2.,levels=[0.,1.])


title('%s SLP [Blu] and 800-500 mb Height [Ylo] over Snow Line [Wht]' % times[i])

savefig('temp_plot%03d.jpg' % i)
`

未指定任何仓库文件或测试。首先使用相同的 longitude_grid、latitude_grid、var、contr 和 snow 输入，复现报告中展示的 Basemap lcc projection 和 contour 调用；完成的标准是确定 contour lines 出现意外尖峰或交叉的原因，并确认修正后的绘图行为不再显示这些 artifacts。

由索引模型根据 Issue 内容生成。