Turbulence in the Lowest Layer of the Atmosphere (3) (Fluctuations of air temperature and their related phenomena)

Abstract

Fluctuations of air temperature in the air layer up to 15 meters above the ground were measured by resistance thermometers (which were made of bare nickel wire, 0.03mm in diameter and about 80cm long, stretched in the space without protecting cover). This thermometer was inserted in one arm of a Wheatstone bridge and the unbalanced current was lead to an electromagnetic oscillograph. The errors that occur in the measurement are discussed. They consist of those induced by the wind pressure, insolation and time lag of the thermometer. Their magnitudes are generally less than 0.04°C, on the other hand fluctuations of temperature are about 0.4°C. So, errors described above are negligible in the measurement of temperature fluctuation. The magnitude of fluctuations of air temperature is 0.3_??_0.4°C in the air layer 1 meter above the ground and the magnitude decreases to 0.2_??_0.1°C in the air layer 15 meters above the ground. Timely and spacial correlations of air temperature fluctuations (R_ξ and Ry) are obtained. R_ξ is expressed approximately by the exponential curve e^-μξ, and the magnitude of is about 8_??_16 sec. (where T is the value ofξ at which R_ξ first cuts the ξ-axis.) Ry is positive even at y=14 meters. The values of correlation are larger than usual when the air temperature of the ground is increasing rapidly. It is discussed that fluctuations of temperature are not wholly due to the mixing phenomena (i.e. the random motion of the lump of air).