An experimental seasonal weather forecasting has been made since the fall of 1951. Assuming 20-,25-,35- and 65-day periodicity in the pressure and temperature change,5-day mean chart and 5-day mean temperature were forecasted for the following 80days, and such forecasts were confirmed to be possible. Next, a brief consideration was given for th e mean synoptic pattern and 700 mb or 500 mb chart was found to be preferable for the seasonal weather forecasting. Thirdly,25-day periodic i ty in solar activity was proposed as the probable cause of 25-day periodicity in the meteorological phenomena. And some analyses were made on such a hypothesis.
The measurement of spla s h amount from the rain gauge wind shield is carried out for three droplet diameters of 2.4,5.0 and 6.6 mm fallen from a height of 6.2 m. The splash is found to be of the order never negligible in actual rainfall observations. Prevention by means of wire gauge spread over the wind shield is investigated and only the gauge mesh width less than 1 mm is found effective. The influence of wind is,, also tested, which can be avoided by the 1 mm mesh wire gauge.
A Speedovane (an experi m ental combination wind vane and anemometer) is fitted with electric heaters and tested for about ten days in March 1953 on the summit of Mt. Fuji (Station height,3,773 m above sea level). From the test the total heater capacity of 650±70 watts is found sufficient for the anti-freezing purpose in ordinary icing conditions.