Air temperature dependencies on the structure of thermometer screens in summer at Daejeon, South Korea

Results and accuracy of air temperature measurements made by meteorological thermometers hosted in thermometer screens strongly depend on the structure of the thermometer screen itself. In this study, the experiment was designed and conducted to understand the effect of radiation on air temperature observation. In order to control radiation sensitivity of thermometer screen, an umbrella made of Al alloy was installed over the thermometer screen (KTU). Air temperatures measured from five thermometer screens have been studied for several weather conditions using a 2-month field experiment at Korea Research Institute of Standards and Science (KRISS). The experiments comprised two version of KRISS type, which artificially ventilated thermometer screen (KTE and KTU) and three naturally ventilated round-shaped multi-plate thermometer screens (BT1, BT2, VT). The results showed that the air temperature of the KTU was approximately 0.10-0.50 degrees C lower than the other group of thermometer screens without an umbrella, which blocked direct solar radiation. During the night, the umbrella minimizes the longwave energy from the KTU to the atmosphere. So the air temperature was roughly 0.10-0.18 degrees C higher than that of the other group without the umbrella. It is confirmed that the umbrella installed over the thermometer screen minimizes the radiation sensitivity of the thermometer screen, and it has a significant effect on air temperature measurements.