Papers in Meteorology and Geophysics
Online ISSN : 1880-6643
Print ISSN : 0031-126X
ISSN-L : 0031-126X
Volume 25 , Issue 3
Showing 1-4 articles out of 4 articles from the selected issue
  • Iwao Tsuchiya
    1974 Volume 25 Issue 3 Pages 147-158
    Published: December 25, 1974
    Released: December 11, 2012
    Four observations of surface temperature of the urban area of Tokyo were performed making use of several airborne remote sensing methods on bright sunny afternoons during summer.
    In the first observation (August 30,1971; NATIONAL ER2001 Infrared Thermometer), it became clear that the surface temperature of a river with a vast amount of water has the lowest temperature, natural or near natural forests have the next lowest temperature, an urban area with many highways is hotter than a suburban area with greenery, and a main street with heavy traffic is the hottest. The second observation (August 4-5,1972; NATIONAL ER2002 Infrared Thermometer) revealed the fact that there are many cases requiring +5+10°C corrections of the airborne records on heated roads and buildings.
    The detection of a thermal complex which corresponds to an experiment of thermal convective circulation under the inversion layer in a stratified wind tunnel and the indication of the environmental temperature of roadside trees in the heated urban area are major results of the third observation (August 11,1972; AGA Thermovision 680). Seismological Section, Japan Meteorological Agency, Tokyo
    In the fourth observation (August 19,1972; DAEDALUS Scanning Radiometer: Digicolor) two thermal maps were analyzed. The first is that of a residential area and the second of a densely populated urban area comprising several large green zones such as the Imperial Palace Grounds. Lower surface temperatures on the leeward side of large green zones and wide rivers (the Sumida and the Arakawa rivers) were clearly noticed.
    These observational results suggest the following: Urban air circulation becomes a very complicated regime by compounded heated and cooled areas of various scales under the developed thermal inversion during the sunny days in summer. Such circulation causes a very complicated flow of polluted air resulting in several densely polluted spots in the suburban area.
    Download PDF (4672K)
  • [in Japanese]
    1974 Volume 25 Issue 3 Pages 159-175
    Published: December 25, 1974
    Released: December 11, 2012
    Influence of the sea surface temperature on the stratification of airmass and cumulus activity over the East China Sea in the pre-summer rain season is studied on the basis of data of Experimen t of Severe Rainstorms Research Project.
    While the very warm water is distributed over the Kuroshio region in the southeastern part of the East China Sea, there is a cold water pool in the central part of the East China Sea.
    The conditional unstable stratification of the subtropical airmass, which flows over the cold water pool, is modified into a very stable stratification.
    The airmass, which flows over the Kuroshio region, on the other hand, maintains its conditional instability.
    The airmass modification over the cold water pool is simulated in the simple numerical experiment with equations of heat and moisture diffusion.
    The influence of the sea temperature on the cumulus activity is examined by a statistical analysis of the radar echo distribution. The result of the analysis shows that cumulus convections are suppressed over the cold water pool.
    Download PDF (2313K)
  • Douglas J. Sherman
    1974 Volume 25 Issue 3 Pages 177-195
    Published: December 25, 1974
    Released: December 11, 2012
    It has been observed that h igh level Clear Air Turbulence (CAT)occurs frequently in places such as Japan and Australia, where a fairly strong jet stream crosses a chain of mountains. If a suitable size mountain occurs somewhere in a mountain range, it is shown that the shear stresses generated by lee waves under conditions of a simple (triangular velocity profile) jet stream, and a fairly realistic (ICAO standard) temperature profile are well able to explain the presence of turbulence. The thickness of the strong shear layers is similar to the observed thickness of typical patches of turbulence. However under the conditions mentioned, it is found that strong shear layers occur to very great heights in the atmosphere, whereas much of the data on frequency of occurrence of CAT tends to show lower probabilities of occurrence at higher altitudes.
    Download PDF (2454K)
  • Ichiro Isozaki, Takeshi Uji
    1974 Volume 25 Issue 3 Pages 197-231
    Published: December 25, 1974
    Released: December 11, 2012
    Accurate and detailed es timation of marine surface winds is needed for the practical application of numerical models describing ocean wind waves and storm surges. Actual surface winds are essentially turbulent and variable because of the critical influence of complex surface structure, atmospheric stability, etc. Especially on the marine surface, parameterization of the winds requires ultimately a knowledge of the process of wave generation because of the mutual exchange of the momentum between winds and waves. So the theoretical estimation of real surface winds is very difficult and empirical formulas have been used for practical purposes.
    Recently, BLACKADAR (1965) and CARDOND (1969) proposed a method of marine surface wind estimation based on a theoretical atmospheric boundary layer model. It is a two-layer baroclinic model for the marine boundary layer. The object of the present paper is to examine several features of their model and make an evaluation of it preliminary to operational use.
    As seen in Fig.1, the atmospheric surface boundary layer is assumed to be separated into two regions: surface layer and Ekman layer. In the surface layer, the Coriolis parameter is neglected, the turbulent transfer coefficient for momentum (Km) increases almost linearly with height, and the wind stress is constant. The vertical wind profile is represented by Equation (A.1.8) in this layer. The height of the surface layer (h) is assumed to be specified explicitly in terms of the external parameters, and Blackadar's formulation (2.1) is adopted. The effect of the wave motion on the structure of the surface wind is taken into consideration indirectly in the specification of the surface roughness parameter which is reprseented by Equation (A.1.27).
    In the Ekman layer, Km is constant, the wind stress decreases with height, and the geostrophic wind components ug, υg and vg are assumed to be linear functions of height. The vertical wind profile is specified by Equation (A.1.30), which is the so-called Ekman's solution.
    Equation (A.1.30) is connected with Equation (A.1.8) with the boundary condition (2.5) through the height h, and the inflow angle (ψ) and the friction velocity (U*) are represented at the height h by Equations (A.3.16) and (A.3.17) respectively. With the equations for stability length (A.1.12), friction velocity (A.3.17)and surface roughness parameter (A.1.27), the surface layer wind distribution is completely described. These three equations can be solved simultaneously for U* using the iteration technique which is shown in Fig.2.
    Computation of the winds to examine the model was made over the Western North Pacific every six hours from 5, Jan.1972 through 12, Jan.1972. The input data are sea level pressure, sea surface temperature and surface air temperature at each of the grid points spaced 150 km apart.
    In the prese n t paper, the computations at OOz,11, Jan.1972are described. Fig.9 shows the distribution of wind velocity which is computed by use of the two-layer surface wind model. Fig.10 is the distribution of wind velocity which is obtained from the analysis based on the ship observations. The frequency of the velocity difference between computed and analysed winds on the grid points is shown in Fig.11. The standard deviation of the velocity difference is 3.05 m/s, and the computed wind velocity is 1.77 m/s smaller than the analysed wind velocity on the average.
    Fig.15 shows the relationships between the friction velocity and the surface wind speed.
    The relationship obtained from the two-layer surface wind model agrees reasonably well with that obtained from the analysis of many observations by Kuznetsov (1970).
    Two computations of ocean wind waves by the procedure of ISOZAKI and UJI (1973) were performed from 5, Jan.1972 through 12, Jan.1972. In Test-1, the wind data obtained by synoptic analysis based
    Download PDF (4304K)