The range of micrometeorological diversity in the biological environment

Abstract

The range of temperature and humidity conditions that can exist simultaneously at or near the ground surface on a bright summer day in a temperate climate are shown in a diagram. Cool and warm conditions are defined as having respectively a lower and a higher temperature than the air at a height of 1.50 m above the surface of the ground. Similarly, humid and dry conditions are defined by a lower and a higher saturation deficit (S.D.), respectively. Cool, humid conditions are found in the open shade where only diffuse solar radiation is received. In high reed vegetations on wet soil, temperatures can lie 8°C below that of the free atmosphere and humidity is close to the saturation point. Warm and humid conditions are found in thin vegetations on damp soil with a temperature excess of up to 10°C and a strongly reduced S.D. In dry grassland, air temperatures 1 cm above the ground are up to 20°C higher and S.D. up to 40 mm Hg higher than at a height of 1.50 m. On suitably oriented slopes covered with dark organic material, surface temperatures can reach 50°C above the air temperature.