Micrometeorological Characteristics in a Sand Dune (I) : On the Heat Balance Properties

he micrometeorological environment in which plants and animals live changes drastically within a few centimeters from the surface into the soil or into the air. The properties of this phenomena are conspicuous in a sand dune. In this paper，we present the observation results of heat balance properties in a sand dune，and compared these results with the numerical experiments results. Numerical experiments for obtaining the diurnal changes in soil temperature were made by giving values to the boundary conditions，that is，the wind velocity，the air temperature and vapor pressure at a height of 100 meters，as well as the conductivity of the soil and the soil temperature at a depth of 1 meter. The resu1ts obtained in this study can be summarized as follows; (1) When the heat capacity and heat conductivity are small，the soil temperature near the surface rises higher during the day and lower at night，compared with a large heat capacity and heat conductivity. These theoretical results coincide with the observation results. (2) In the case of a wet surface，latent heat flux increases，but energy storage in the soil is very complicated by the thermal properties of the soil. As mentioned above，fairly reasonable agreement can be obtained between simulation experiments and observation results，but to predict more accurately the heat flux budget in a sand dune，we need to properly specify the degree of soil moisture and thermal property

Measurements of the Wind generated by Desert Environment Wind Tunnel (Constant Speed Wind and Periodically Varying Wind)

Wind characteristics generated by the wind tunnel named Desert Environment Wind Tunnel, which can generate arbitrary pattern of wind speed variation by changing the angle of pitch of the blower blades, were investigated with both of a hot-wire anemometer and a ultrasonic anemometer. Distributions of the wind velocity components (v, w) in a plane perpendicular to the mainstream (u-direction), whose wind speed varies like a sine wave, were measured downstream at x = 1.5m from the exit of wind tunnel nozzle. The experimental results revealed that the flow expands when it accelerates and, in reverse, the flow contracts then slowing down