Siberian Tiger Exhibit - Viewing Area

For details, see my review http://www.zoochat.com/22/review-san-francisco-zoo-158768/#post334582

What are the rows of metal bars that run horizontally above the sheet glass?

They provide a bit of shade to visitors standing near the glass, which is rarely needed in this climate!

I wonder if they are an effort to reduce glare on the glass (or plexi?)

Both answers seem reasonable (shade & reduce glare) and make sense, but rarely is there sun at the San Francisco Zoo!

Yes, but full sun is not required for glare. You'll see alot of reflection of the pavement on the glass on any day. The shade structure helps somewhat. And given the mist and spray there, I wonder whether the view really works much of the time?
But of course, this was never about seeing tigers

I see how glare could be a problem; but viewing the tiger is still possible, because you should be able to see within a few hundred feet even with fog.

Ah great. I was thinking of condensation on the glass actually

Note: That's a remarkably clean image of the plexiglass sheet that's gone up around all of the cat grottoes. It doesn't look like that today. The rather harsh marine climate has caused some oxidization around the edges of the glass in addition to the collection of graffiti etched into the panels. In short, it doesn't provide the greatest viewing opportunities.

Also, are we calling the metal overhang a "shade structure"? Those aren't panels running along the top, they're essentially metal strips (I believe) intended to discourage visitors from climbing into the enclosure. At any rate, they're ugly as sin and should be removed posthaste.