Extreme Maximum Land Surface Temperatures

Abstract

There are numerous reports in the literature of observations of land surface temperatures. Some of these, almost all made in situ, reveal maximum values in the 50°?70°C range, with a few, made in desert regions, near 80°C. Consideration of a simplified form of the surface energy balance equation, utilizing likely upper values of absorbed shortwave flux (≈1000 W m?2) and screen air temperature (≈55°C), that surface temperatures in the vicinity of 90°?100°C may occur for dry, darkish soils of low thermal conductivity (≈0.1?0.2 W m?1 K?1). Numerical simulations confirm this and suggest that temperature gradients in the first few centimeters of soil may reach 0.5°?1°C mm?1 under these extreme conditions. The study bears upon the intrinsic interest of identifying extreme maximum temperatures and yields interesting information regarding the comfort zone of animals (including man).