Yeah that was my impression too at first. After re-reading again, the NOAA sensor also used a passive shield. So it is better in matching the NOAA readings. But it could also be said the aspirated Davis was more sensitive than the passive shielded Davis or official NOAA unit.
I also noted somewhere that they recommend the rain guage be separated from the screen, which I thought was a bit strange.
From what I can work out / guess, the rain gauge being black convects the air up past the screen, which to me is a good thing as it works like a tiny fan bring air past the temp sensor, particulary on a still day with no breeze. When there is a breeze, then it should not create any issues at all.
Also, the simply fact that the size of the rain guage also shades the screen, particulary during the middle of the day... remembering that the base of the rain guage is not absorbing heat like the rest of the guage as it is also in the shade.
Not having the rain guage above would in my mind, necessitate the addition of FARS, and would also skew this previous study made, with a more pronounce difference between the FARS and passive, as well is the base temp sensor.
