The image shows sea surface height relative to normal ocean conditions for this time of year.

这张图像显示了当前海面与每年此时正常情况下之间的高度差异。

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Let's break the name down. The "normal" is a vector perpendicular to a surface, which we can use to calculate lighting.

首先我们从名字上开始分析，所谓“法线”指的是垂直于平面的向量，我们使用这个来计算光照。

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And, in terms of direction, it will be normal to the surface.

对于方向，则是曲面的法方向。

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But Dr Dial wanted to be sure, so he compared the accomplishments of normal partridges with birds that had their wing feathers clipped to half their normal surface area, and to even less fortunate fowl whose main flight feathers were entirely plucked.

ECONOMIST: Birds that don't fly may be using their wings to run uphill

Storm surges have the potential to be dangerous because they involve a great upwelling of a stretch of ocean - intense low pressure at the heart of a storm literally tugs the sea surface above its normal level to create a massive bulge.

BBC: Legacy of Britain's great flood

Now he can congratulate himself that, on the surface at least, things are back to normal.

ECONOMIST: Eisner fights on