Intercomparison of In Situ Sensors for Ground-Based Land Surface Temperature Measurements

Area of Science:

• Earth and Environmental Sciences
• Atmospheric Science
• Remote Sensing

Background:

• Land surface temperature (LST) is a critical variable for understanding land-atmosphere energy exchange processes.
• Accurate ground-based LST measurements are essential for validating satellite data and improving climate and weather models.

Purpose of the Study:

• To assess the quality of in situ LST measurements.
• To evaluate quantitative uncertainties in ground-based LST data.
• To compare different methods of LST measurement.

Main Methods:

• Intensive field experiments were conducted at NOAA's ATDD in Oak Ridge, Tennessee.
• Compared LSTs from infrared temperature sensors (IRT), pyrgeometers (LWR), a forward-looking infrared camera, thermocouples (TC), and near-surface air temperature (AT).
• Extended analysis to four US grassland sites for annual and seasonal differences.

Main Results:

• Infrared temperature sensors (IRT) showed good agreement with brightness temperature (BT) (bias <0.23 °C, RMSE <0.36 °C).
• Daytime LST from IRT and thermocouples (TC) agreed well (bias = 0.26 °C, RMSE = 0.67 °C), outperforming longwave radiation (LWR) measurements.
• Nighttime LSTs from IRT, TC, and LWR showed small differences (<0.47 °C), while air temperature explained >81% of LST(IRT) variance with higher bias and RMSE.

Conclusions:

• Infrared temperature sensors provide reliable in situ LST measurements, suitable for validation and modeling.
• Longwave radiation measurements showed greater discrepancies compared to IRT and TC, especially during daytime.
• Air temperature is a less reliable proxy for LST, particularly at night, with significant differences observed across various conditions.