A global comparison between station air temperatures and MODIS land surface temperatures reveals the cooling role of forests

• Published in: Journal of Geophysical Research Vol. 116; no. G3
• Main Authors: Mildrexler, David J., Zhao, Maosheng, Running, Steven W.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-09-2011
• Subjects: Agricultural land; Air temperature; Aqua/MODIS land surface temperature; Climate change; Cooling; Deciduous forests; Earth; Energy balance; forests; Geobiology; Global temperatures; Grasslands; High temperature; Land surface temperature; maximum temperature; Plant ecology; Remote sensing; surface-atmosphere energy fluxes; Thermal energy; transpiration; Water; WMO air temperature
• ISSN: 0148-0227; 2169-8953; 2156-2202; 2169-8961
• DOI: 10.1029/2010JG001486

Most global temperature analyses are based on station air temperatures. This study presents a global analysis of the relationship between remotely sensed annual maximum LST (LSTmax) from the Aqua/Moderate Resolution Imaging Spectroradiometer (MODIS) sensor and the corresponding site‐based maximum air temperature (Tamax) for every World Meteorological Organization station on Earth. The relationship is analyzed for different land cover types. We observed a strong positive correlation between LSTmax and Tamax. As temperature increases, LSTmax increases faster than Tamax and captures additional information on the concentration of thermal energy at the Earth's surface, and biophysical controls on surface temperature, such as surface roughness and transpirational cooling. For hot conditions and in nonforested cover types, LST is more closely coupled to the radiative and thermodynamic characteristics of the Earth than the air temperature (Tair). Barren areas, shrublands, grasslands, savannas, and croplands have LSTmax values between 10°C and 20°C hotter than the corresponding Tamax at higher temperatures. Forest cover types are the exception with a near 1:1 relationship between LSTmax and Tamax across the temperature range and 38°C as the approximate upper limit of LSTmax with the exception of subtropical deciduous forest types where LSTmax occurs after canopy senescence. The study shows a complex interaction between land cover and surface energy balances. This global, semiautomated annual analysis could provide a new, unique, monitoring metric for integrating land cover change and energy balance changes.
Key Points
Radiometric LST provides additional information on surface energy fluxes
Only forests maintain a strongly coupled LSTmax/Tamax relationship
Annual LSTmax/Tamax relationship presents new ways to track climate change