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occasions. No.10 typhoon warning signal was hoisted in Sep- tember when the centre of typhoon Gloria was approaching. Storm warning signals were displayed for a total of 293 hours and the strong monsoon signal for 380 hours.
For details of the year's weather, see pages 325, 326 of Chapter 22.
METEOROLOGICAL RESEARCH
Less time was devoted during 1957 to research than in previous years owing to the extra commitments associated with the opening of the central forecast office and with the International Geophysical Year. New seismological equip- ment was installed, but Hong Kong's main contribution to the Geophysical Year was in the field of meteorology. Radiosonde ascents were increased to two a day, and both radiosonde and radarwind observations were carried out to higher levels than formerly.
Work continued on a long-term project to determine whether afforestation would affect the run-off of surface water in Tai Po Kau Forestry Reserve by increasing con- densation in foggy conditions. The re-analysis of tracks of typhoons and tropical depressions for the period 1884 - 1953 was completed and publication commenced. In addition, monthly rainfall maps were prepared for Hong Kong and the New Territories. Papers entitled 'A Climatological Study of Tropical Cyclones over the China Seas' and 'The Horizontal Distribution of Rainfall over a Small Area in the Tropics' were presented by the Director at the Ninth Pacific Science Congress at Bangkok, when he also convened a Symposium on Intertropical Convergence Zone, Thunder Storms and Tropical Clouds.