Based on the data in the Marshall Islands obtained in 1956 and 1958, vertical velocities and heat source associated with tropical wave disturbances are estimated and the energy transformation of the disturbances are examined. An approximate estimate of the upward transport of sensible and latent heat by small-scale convective motions is also obtained. Eddy available potential energy is generated by the heat of condensation and is transformed to the eddy kinetic energy in the upper troposphere centered about 300mb. Energy flux is upward above the level about 300mb and downward below that level. Other terms of energy transformations such as the conversions from mean kinetic energy and from mean potential energy are one or two order of magnitude smaller than terms of generation and conversion of eddy available potential energy. The sensible and the latent heat supplied from the sea surface is transported upward by the cumulus convecsions and strong convective transport corresponds to the upward motion of the large-scale disturbances. A non-dimensional heating parameter η(p) is also obtained and is compared with that used in theoretical studies.
Average structure of wave disturbances are examined from the data in the Marshall Islands obtained in 1956 and 1958. Four kinds of disturbances are found for 1956. The first is the Yanai-Maruyama wave which propagates westward with 5-day period and wavelength of 8, 000km. The second is the= n=1 type disturbance which propagates westward with 5-day period and wavelength of 5, 000km. The third is the Kelvin wave which propagates eastward with period longer than 10 days and wavelength longer than 10, 000km. The fourth is the westward propagating wave whose period is longer than 10 days and wavelength is 5, 000km-9, 000km. Three kinds of disturbances are found for 1958. The first is the Yanai-Maruyama wave similar to that obtained for 1956. The second is the lower tropospheric disturbance which propagates westward with 6-day period and wavelength of 2, 500km. This wave is similar to that reported by Wallace and Chang (1969) and Chang et al. (1970). The third is the wave which propagates westward with period longer than 10 days and wavelength about 10, 000km. These disturbances maintain their kinetic energy by the conversion from eddy available potential energy. The average structure of these waves are constructed and compared with some theoretical results.
A method of spectral analysis of traveling waves, based on time-wise Fourier series analysis of zonal harmonics, is presented and illustrated by applying it to the 500 and 10 mb levels at 45°N for January 1965. The method of analysis is compared to that published recently in this journal by Hayashi.
As an extension of Nitta and Yanai (1969) the stability properties of a barotropic easterly current with a sine-profile jet are studied in more detail. The barotropic vorticity equation on a β-plane is solved by the finite difference method, as was made in the previous study. It is found that the stability properties of the easterly current are different from those of the westerly current in several respects such as a possibility of the existence of an unstable wave which propagates faster than a maximum velocity of an easterly current, the existence of many unstable waves of various meridional modes, strong dependency of wave properties on lateral boundaries, latitudinal profiles of wave amplitudes (as well as the direction of wave axis) and so on. It is also found that the β-plane approximation is justified only when we discuss two unstable waves of the lowest and second meridional modes.
Stability dependence of the turbulent fluctuations of vertical wind velocity, temperature and humidity are discussed. Semi-empirical expressions of σw/u*, σθ/|θ*| and σq/|q*| are developed by assuming a simple shape of the variance spectra. The spectra have been computed using an analog computer. The data were obtained at Davis, California in 1967 using sonic anemometers and dry and wet thermocouples. The experimental data of σqw/u*, σqθ/|θ*| and σqq/|q*| agree with the theoretical curve throughout the analyzed range of stability within the accuracy of the data. The results indicate a similarity between temperature and humidity fluctuations. This similarity is found both in the behavior of σqθ/|θ*| and σq/|q*| with stability as expected from the theory, and in the variations of the input frequencies with stability.
Considerations of the sintering process in the atmosphere were carried out by measurement of the rate of growth of the ice neck between “sintered frozen cloud particles” observed at Syowa Station, Antarctica . As a result, if the sintering process alone contributed to the growth of the ice neck between frozen cloud particles in the atmosphere, it was considered that the sintering mechanism was not only by evaporation-condensation but also by volume diffusion and plastic or viscous flow.