quiver arrows reverse in all polar projections except orthographic. Why?

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Issue 类型
缺陷
描述清晰度
基本清楚
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停滞
技术栈
python
领域
data-visualization

调研方向

首先运行链接的脚本 plot_quiver_bug_test.py，并比较 Southern Ocean 在 orthographic、polar stereographic、Lambert azimuthal 和 azimuthal equidistant 下的结果。跟踪 quiver 向量如何经过每种投影进行变换；完成的标准是：在极地投影中，向东的向量能够像在 orthographic 投影中一样保持正确的方向。

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描述

Hi

I'm trying to plot vectors in the Southern ocean using basemap and matplotlib.
To illustrate my problem I've created a zonal jet at 60S.
I have U and V as 2D arrays and lon and lat as 1D arrays, all with cyclic point added and lon is from -180 to 180.
If I plot in orthographic projection the vectors correctly shows eastward motion, but if I use any of the polar projections (spstere, splaea spaeqd) the vectors reverse!
This is really strange and oddly enough it does not seem to happen if I make the same plot over the North Pole.

I've noted that in the southern hemisphere lon_0 has a different meaning for orthographic projection than for spstere, splaea etc.
So to orient the maps the same way I must pass lon_0=0 in orthographic projection and lon_0=180 in polar stereographic projection if I plot southern hemisphere.
But this is not the case in the Northern hemisphere.
Could this be part of the problem?

Here's the script that creates the results:
https://dl.dropboxusercontent.com/u/86754720/plot_quiver_bug_test.py
Here's the contourf of u and v
https://dl.dropboxusercontent.com/u/86754720/velocity_bug_contourf.png
and here are the vectors
https://dl.dropboxusercontent.com/u/86754720/velocity_bug_quiver.png

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