Ground surface temperature has become an important component of weather. The temperature of the ground surface can be more than 10 C above air temperature on a sunny day and up to 10 C below air temperature on clear nights, when the surface loses heat by radiation to the cold infinity of outer space. Like most environmental sensors, infrared sensors have become more accurate and lower cost over the past 10 years.
Infrared (also called non-contact) sensors determine surface temperature using a portion of the longwave thermal radiation emitted by the object of measurement. This type of sensor is used to determine the Earth’s surface temperature from outer space.
The Observatory uses two IR sensors that measure the temperature on the southeast, and southwest sides. The temperatures are nearly identical, except when shadows from trees temporarily reduce the temperature.