The present writers made observations of the cloud on the day of the total eclipse of the sun, 21st Sept., 1941, by using a photo-theodolite, a whole sky camera and a cinematograph. The conspicuous phenomena observed were the increase of Alto-cumulus and the decrease of Cumulus as the eclipse proceeded. Besides these, a figure change of the cloud and the existence of several saturation layers were observed, but any remarkable change in the direction of cloud movement was not.
The problem of isallobaric winds is important from practical and theoretical points of view. We discussed the problem in detail adopting the method by H. Phillips. One of the results is that the “Relaxationszeit” r due to H. Ertel is given by where c is the coefficient of friction of GoldbergMohn and λ the coriolis-factor. Further we gave a method which makes it possible to treat the non-linear terms in the equation of hydrodynamics and obtained some important results.
We observed the Lenticularis-clouds from May, 1938, to April, 1941, in order to investigate their formations, and obtained thirty-two data. The results obtained from this investigation are summarized in the following. 1) It is necessary for the formation of the Lent.-clouds, that the wind-velocity at an upper layer is strong and that there are inversions in the Lent.-clouds layers. 2) The Lent.-clouds are most liable to appear during 14-16 O'clock. 3) The durations of appearance of the Lent.-clouds are generally less than one hour. 4) The wind-velocity at the ground is generally strong when the Lent.-clouds have appeared. Whenever the Lent.-clouds were observed in SENDAI District, the air temperature at the ground quickly increased and the humidity decreased. It was known that this high temperature and low humidity had been due to Foehn, and that the Lent.-clouds that appeared in SENDAI District were formed by the Foehn-waves. Next, we discussed the Lent.-clouds on the basis of the Foehn-wave Theory by J. KÜPTNER. We classified the pressure distribution into 4 types: A, B, C and D type. For each type, strong west wind was blowing in upper layers and a high pressure was approaching.