The ninth issue of Online Quiz Games - Rain

13 July 2015

The Earth's atmosphere is composed of different types of gases, while water vapour constitutes a small part of them. When there is upward motion of air, air parcel will cool as it rises due to expansion. Cooler air parcel has smaller capacity to contain water vapour and hence water vapour will condense into water (or ice) droplets. These water droplets come together to form clouds. When they become too large and too heavy to remain suspended in the air, they will fall from clouds to form rain.

The mean annual rainfall in Hong Kong is about 2 400 millimetres. There are significant differences in the mean annual rainfall for different parts of the territory. More than 3 000 millimetres of rainfall are recorded at the vicinity of Tai Mo Shan in a year on average. In Hong Kong, about 80% of the rain falls between May and September. June and August are usually the wettest months. The theme of this issue of the quiz games is about rain. Do you know what types of weather systems will bring about rainstorms in Hong Kong? Please come and play the new issue of the quiz games. This issue will end on 26 July.

HKO's webpage: http://www.weather.gov.hk/education/online_quiz/intro_e.htm

HKO's mobile webpage: http://m.weather.gov.hk/education/online_quiz/m_intro_e.htm