
Isohyet Chart
The isohyet chart for Hong Kong is obtained by integrating rain-gauge data and
weather radar data.
More than 90 automatic rainfall stations exist in Hong Kong. They are operated by the
Hong Kong Observatory, the Geotechnical Engineering Office and the Drainage Services
Department. The rainfall stations automatically report rainfall measurements to the
Observatory Headquarters through telephone lines.
Data from the Observatory's weather radars at Tai Mo Shan and Tate's Cairn also provide
estimates of rainfall amount.
For the production of the isohyet chart, estimated rainfall from radar data is correlated
with the observed readings from the rain-gauges. In places where rain-gauges are not dense
enough, rainfall amounts at specific points are estimated on the basis of the correlation.
Readers should beware that by its nature, the isohyet chart serves only to indicate visually
the spatial pattern of rain. It should not be relied upon to derive exact rainfall amounts at
specific locations. Furthermore, this is an automated product generated by computer for quick
reference, erroneous data may slip through quality checks in spite of the best of our intentions.
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