Interestingly enough, former California State climatologist James Goodridge did an independent analysis of COOP stations in California that had gone through modernization, switching from Stevenson Screens with mercury LIG thermometers to
MMTS electronic thermometers.
Most of the stations have changed from using liquid in glass
thermometers (LiG) in Stevenson screens to
electronic Minimum Maximum Temperature Systems (
MMTS) or Automated Surface Observing Systems (ASOS).