The Hong Kong Observatory is enhancing its regional weather information to the public. From today (February 6), the grass temperatures at Tai Mo Shan and King's Park Meteorological Station will be added to the Observatory's "Regional Weather" webpage, adding to the grass temperature information at Ta Kwu Ling.

"Low temperature, in particular frost, can damage vegetation. It is hoped that by providing more grass temperature information to farmers, they can more easily determine if precautionary measures are required to protect the crops on cold winter nights," Senior Scientific Officer of the Hong Kong Observatory Mr C C Chan said.

Grass temperature is the temperature recorded at the ground surface just above short grass. On cold clear winter nights, hoar frost forms by direct sublimation of water vapour onto the grass surface when the surface is cooled below zero degrees Celsius by radiating heat off to space. Frost occurs more frequently over open terrain and on high ground where temperature is generally colder.

The Observatory has disseminated real-time grass temperature information at Ta Kwu Ling automatic weather station since December 2006. Between 5pm and 8am the following morning, real-time readings from the automatic grass temperature measurement systems at Ta Kwu Ling automatic weather station, Tai Mo Shan automatic weather station and King's Park Meteorological Station are available on the following webpage:

http://www.weather.gov.hk/wxinfo/ts/index_e_grass.htm

The webpage will be updated once every 10 minutes.