The water vapor budget in the lower stratosphere over Japan was studied. At Kagoshima and Tateno the observed water vapor mass mixing ratio is explained by a modified Brewer circulation model adding the water vapor source of CH4 oxidation except in spring at Kagoshima. The vertical eddy diffusion coefficient at an altitude of 20.7 km was estimated to be 1.2-1.4×103cm2sec-1 from the vertical profiles of water vapor and the production rate of water vapor by the oxidation of CH4. Seasonal variation of the residence time of water vapor in the lower stratosphere was obtained; minimum in winter-spring (0.3 year) and maximum in fall (0.95 year). Mean vertical velocity of the return Hadley circulation (the descending branch of the Hadley circulation) was estimated to be 0.010-0.035cm sec-1. Water vapor in the lower stratosphere at Sapporo cannot be explained by the same model as Tateno and Kagoshima except in spring. A very low water vapor mixing ratio is observed in spring from Kagoshima through Sapporo and in winter at Sapporo, suggesting some water vapor removal processes. Aerosols in the lower stratosphere make negligible contribution to the water vapor budget except after an extensive volcanic eruption.
The fluctuations of the horizontal and vertical wind components measured by the single head sonic anemometers at six levels in high winds were analyzed. The vertical profiles of wind speed from 10 m to 200 m can be expressed by the power law with the power of 0.3. The dependency on height of the statistical properties of turbulence such as standard deviations and friction velocity is examined. The dependency on height of the integral scale of horizontal and vertical components, and the spectral scale for both components are discussed. The vertical profiles of the gust factor (G) can be expressed by the following equation:
where s is averaging time, D, sampling duration, Z, height. The values of dissipation rate estimated by the spectral method are nearly equal to those by the eddy correlation method and the vertical profiles of dissipation rate can be approximately expressed as ε∝Z-1 (Z≤50 m), ∝Z-2 (50<Z≤200 m).
Atmospheric turbulence caused by the topographical features near an airport is one of the most important factors to be considered in aircraft operation. For, in Japan, many local airports are located in a topographically complicated area. In view of this, we made field observation of topographical turbulence near the Miyakejima Airport, which is located in the lee of a mountain in the winter monsoon season. From the analysis of surface and airborne observations, it was found that topographical turbulence was predominant up to half of the mountain height and decayed in the leeward direction, but extended in the upward direction. The vertical distribution of the dissipation rate of turbulent kinetic energy was estimated from the values of vertical acceleration of the airplane. The vertical distribution of eddy viscosity was also estimated.