COMPARISON OF MAXIMUM MINIMUM RESISTANCE AND LIQUID-IN-GLASS THERMOMETER RECORDS

The replacement of liquid-in-glass (LIG) thermometers with electronic thermometers in the National Weather Service (NWS) cooperative (co-op) network and concern for homogeneous temporal temperature records prom pted this comparison study between the two temperature sensors. This s tudy shows that the new National Weather Service maximum-minimum tempe rature sensors (MMTS) underestimate LIG maximum temperatures by as muc h as 0.6-degrees-C, but are virtually equal to LIG minimum temperature s. The magnitude of differences increases with increasing solar loadin g and decreased wind speeds, apparently due to better ventilation char acteristics of the MMTS shelter compared to those of a cotton-region s helter. Any comparison of MMTS records with the LIG record will theref ore require wind and solar observations. Unfortunately, neither wind n or solar is measured at NWS co-op sites, requiring the use of data fro m the nearest observing station. Obviously, the time of change from LI G sensors to the MMTS is of paramount importance when evaluating long- term temperature change.