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Volume 29 (1978)
- Issue 4 Pages 157-
- Issue 3 Pages 109-
- Issue 2 Pages 35-
- Issue 1 Pages 1-
Volume 29, Issue 3
Displaying 1-4 of 4 articles from this issue
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Nobuhisa Yasuda1978 Volume 29 Issue 3 Pages 109-123
Published: September 15, 1978
Released on J-STAGE: December 11, 2012
JOURNAL FREE ACCESSIt is here tried to clarify the characteristics of turbulence in the atmospheric boundary layer based on the fundamental equations, that is, the Navier-Stokes equation and the first law of thermodynamics. From these fundamental equations, are derived equations which rule the second-order moments involving the turbulent fluctuations of wind velocity and potential temperature. In order to obtain a closed system of equations the equations of third-order moments are derived and MillionshchikoN's assumption on the probability function is assumed. Some simple solutions are analytically examined and the theoretical results are compared with some observational data in the atmospheric boundary layer.View full abstractDownload PDF (2429K) -
Shoin Yagi, Yasusi Okamura1978 Volume 29 Issue 3 Pages 125-140
Published: September 15, 1978
Released on J-STAGE: December 11, 2012
JOURNAL FREE ACCESSVarious one-way nesting techniques so far presented are tested in order to decide the best technique from a practical standpoint. Nesting schemes tested here are:
(1) Schemes with special care to avoid over-specification as a boundary value problem.
i) The scheme with simple extrapolation (referred to as SE-scheme)
ii) The scheme of SundstrOm (1973) (SS-scheme)
iii) The scheme modified by taking acc o unt of gradient value of coarse mesh model in extrapolation (SG-scheme)
iv) The scheme of Okamura (1975) (SO-cheme)
(2) The scheme of Orlanski (1976) with Sommerfeld's radiation condition (O-scheme)
(3) The scheme of Perkey & Kreizberg (1976) in which the tendency is smoothed in the lateral boundary layer (T-scheme)
(4) The scheme with Newtonian damping in the lateral boundary layer
i) Davies' method (1976) (D1-scheme)
ii) The scheme utilizing si m ple Newtonian damping (Do-scheme)
Numerical tests for comparison are done under the fol l o wing conditions:
(1) Tests in which the phase velocity error is given in the outer domain during the forecasting period. (Test 1)
(2) Tests in which isolated disturbance is given in the inner fine mesh domain at intial time. (Test 2)Results of the test are as follows:
(1) T-scheme is the best one because of its least deviation from the control run and the computationally stable results.
(2) Dr-scheme and Do-scheme are the second best. Little difference is found between the results of the two schemes. Damping coefficient used in these tests se e ms to cause more error than in T-scheme because of its inadequately large value.
(3) Among the SE-, SS-, SO-, o-, and SG-schemes, SG-scheme gives the least error. The error in that scheme is the same order as that in D1-scheme within 24 hours foreca s t. But, for longer time integration,, the results of SG-scheme tend to be unsta b l e.
(4) When O-scheme is adopted, results are very sensitive to the way in which the phase velocity of the disturbances near the boundary is estimated.View full abstractDownload PDF (2616K) -
Hiroshi Naruse1978 Volume 29 Issue 3 Pages 141-150
Published: September 15, 1978
Released on J-STAGE: December 11, 2012
JOURNAL FREE ACCESSAn improved thermal diffusion chamber is developed for easy and convenient measurement of cloud condensation nuclei (CCN) in field work. It is designed to involve a faster temperature control system (see Fig.1). In order to use the thermal diffusion cham ber more than usually accurately, a better temperature regulation mode is experimentally investigated. The measurements of the temperatures inside the chamber and the CCN are carried Out and these results are shown in Fig.6 and Table 2. It is shown that the CCN counts in Case 2(Tt>Ta. >Tb) are larger than those in Case 1(Ta>;Tt>Tb), where Tt, Tb, and Ta are the temperatures at the top and bottom of the chamber and of the air introduced. The theoretical calculations and experimental inves t i gations on transient supersaturations are reported by Fitzgerald (1970) and Saxena et al. (1970,1973). According to the calculated results by Fitzgerald and Saxena et al., the values of transient supersaturation in the chamber under the condition at Ta=Tb are larger than in the case of Ta-=-Tt. On the other hand, it is shown by Saxena et al. that these value are dependent upon the relative humidity of the air introduced. As shown in Table 2, the CCN in Case 2 is 1.4 times larger than that in Case 1. It is found that the results of our experiment nearly coincide with those obtained by Saxena et al. The author considers that transient supersaturation occurs in Case 2. From the analysis of experimental results, it is concluded that Case 1 mode is a better regulation mode than Case 2. In August,1976, some measurments of CCN concentration we r e made by the present diffusion chamber in a city of paper mills, Fuji-city, Sizuoka Prefecture. Hourly correlation between CCN and SO2, which has been from the city pollution monitoring station, during the daytime was higher than those between CCN and Aitken nuclei (Figs.7,8, and 9, Table 3). It is also shown (Fig.10) from the supersaturation spectra of CCN measured that the spectra consist of more particles of higher nucleation activity at the time of peak concentration than at other times. This result suggests that sulphates p r oduction from such factories have a positive relationship with the increase of CCN.View full abstractDownload PDF (4711K) -
Shunji Konaga, Katsunobu Nishiyama1978 Volume 29 Issue 3 Pages 151-156
Published: September 15, 1978
Released on J-STAGE: December 11, 2012
JOURNAL FREE ACCESSVery interesting phenomena were observed on board the R. V. Shumpu-Maru, Kobe Marine Observatry, on detached cold eddy from the Kuroshio in seas south of Japan early July 1977. There are ring-like low haline waters in the periphery of the eddy, anomalously high temperature in the central region of the eddy, where cold waters should occupy, and many visual slicks around the central part of the eddy. The ring-like low haline waters might be attributed to the heavy rain in the atmospheric stationary front, called "baiu-zensen", late June in the area., according to Kamihira et al. (1978). Moreover, we propose a mechanism in which a forced upwelling by the seamount generates a convergence zone around the seamount, in which low-haline waters are accumulated.
In regard to the anomalously high temperature region near the eddy c enter, Kamihira et al. attribute the event to the remnant of Kuroshio waters existing just before their observation was made. However, we may be obliged to consider the malfunction of the XBT systems responsible for it, because the current speed is too weak and temperature contrast is too intense to make a dynamical balance. Moreover a thermal fine structure, appearing at about 400 m depth, suggests a large instrumental error in the XBT record. Although we might ascribe the anomaly mainly to the instrumental error in the XBT record, it is possible to explain the generation of a warm core by modification of the mean current due to the topographic effect of the seamount, analogous to a Taylor column.
The configuration of the eddy through its northwestward migration, first compressed to the seamount, then enlarged around it, then again elongated towards northwest and eventually absorbed into the Kuroshio, might apparently be due to the topographic effect of the seamount associated with the generation of the shed vorticity. These problems will be studied in future work.View full abstractDownload PDF (1464K)
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