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I snapped this photo with my cell phone at a fishing harbor in northern Taiwan.

I recognize a weather vane + anemometer, and I suspect the two large, dark things at the tops of poles might be omnidirectional antennas, but the item near the right shaped like an upside-down funnel at the end of a u-shaped tube appeared to be transparent, as if glass or plastic.

I've never seen anything like it. Any thoughts?

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enter image description here

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  • $\begingroup$ Is it really glass? Otherwise I might say it's possibly an inlet for an ozone monitor or other gaseous air quality monitoring equipment. $\endgroup$
    – f.thorpe ♦
    May 15, 2018 at 6:13
  • $\begingroup$ @farrenthorpe good point, I don't know the material of course, so I've changed the title. I'm curious though, why the "otherwise"? $\endgroup$
    – uhoh
    May 15, 2018 at 6:19
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    $\begingroup$ I've never seen a glass inlet... only metal. The transparency of it is throwing me off. $\endgroup$
    – f.thorpe ♦
    May 15, 2018 at 16:12
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    $\begingroup$ @farrenthorpe This may not be glass inlet but transparent plastic inlet. Transparent glass and plastic inlets are quite common for pollutant gas measurements as it is easy notice any insect stuck in the inlet. In fact, metal inlets are usually avoided for gas measurements as some of gas can react on its surface. Metal inlets are mostly used for aerosol (particles in the air) sampling since the particles can be charged particles can stick to the plastic surface (any non-conducting surface) whereas when the metal inlet is grounded it will be insensitive to the charge of the particles. $\endgroup$
    – Harish
    Jun 12, 2018 at 11:40
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    $\begingroup$ One usually sees metal are not really a metal inlet but an enclosure through which other inlets (like plastic or glass) are passed. Metal enclosure provides structural support to the flexible inlet. $\endgroup$
    – Harish
    Jun 12, 2018 at 11:43

1 Answer 1

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The upside down funnel-shaped attachment is used to prevent rain-water getting inside the inlet of instruments which analyse ambient air. Usually, these instruments are air pollution monitoring instruments like ozone analyser, carbon monoxide analyser, particle concentration analyser, etc.

One may think why can't just use U-shaped tube (inlet). In case of U-shaped inlet, rainwater falling on inlet will eventually roll down near the entrance and will be pulled in with air due to strong flow. Funnel shape will have smaller flow near the wider opening and prevents water from getting into the air stream.

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  • $\begingroup$ Thanks for the answer! It makes perfect sense. I've added a zoom of the same image, there even seems to be a bulb between the funnel and the tube, which might also be consistent with the same explanation. $\endgroup$
    – uhoh
    May 15, 2018 at 6:21
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    $\begingroup$ @uhoh Makes sense. Indeed this definitely isn't an official meteorological reporting station - as this FAA specifications details, "sensor exposure must strive to minimize or eliminate the effects of man-made or geographical obstructions." In other words, truly representative synoptic sensors will be away from buildings (as much as possible), not on them! So it appears more likely to be part of an urban monitoring project (or just an amateur station without greater purpose, but doubtful, given I'd never seen that instrument!) $\endgroup$
    – JeopardyTempest
    May 15, 2018 at 17:24

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