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  • A silent "guard" of Hong Kong over the past 30 years - Huangmao Zhou automatic weather station

  • Thursday, 17th December 2015

Huangmao Zhou (HMZ) is located at around 50 km south of Hong Kong. It gets its name because a kind of yellow reed grows abundantly on the island[1]. The Hong Kong Observatory (HKO) and the Guangdong Meteorological Bureau (GMB) signed a cooperation agreement in 1984 to jointly establish automatic weather station (AWS). Through close collaborative efforts of the staff from both sides, the AWS at HMZ started operation on 10 July the following year. The then AWS transmitted weather data including wind direction, wind speed, air temperature, pressure and rainfall amount at half hourly interval back to HKO where the data were re-transmitted to the China Meteorological Administration (CMA) and GMB via meteorological telecommunication circuits[2]. The capability in monitoring inclement weather in the vicinity of the Pearl River Estuary has thus been greatly enhanced.

The inauguration of HMZ AWS carried historical meaning. From 1897 to 1941, HKO received meteorological observation reports from Gap Rock (now known as Wenweizhou Dao)[3]. Due to World War II, nil further observation report from Gap Rock was made available on HKO's weather chart since 30 November 1941. The lighthouse on Gap Rock was even dismantled on 7 December of the same year[4]. HMZ is located at a close distance of only about 2 km northeast of Gap Rock (Figure 1). The operation of HMZ AWS could thus somehow be seen as a continuation of meteorological observations from Gap Rock.

Figure 1

Figure 1      A photo showing the locations of Huangmao Zhou automatic weather station and Wenweizhou Dao (A lighthouse was built on the island).

In the past 30 years, HMZ AWS has served as a major outpost of HKO in monitoring weather approaching from the sea. In late July 2012, Severe Typhoon Vicente affected Hong Kong and it necessitated the issuance of the No. 10 Hurricane Signal. Vicente was closest to Hong Kong in the early hours of 24 July, passing about 100 km to the southwest of HKO. Vicente underwent rapid intensification within around 30 hours prior to its closest approach to Hong Kong, strengthening by three categories from a tropical storm to a severe typhoon[5]. On the night of 23 July, winds recorded at HMZ AWS soared quickly to hurricane force or above (i.e., 118 km/h or above) and reached a maximum of around 180 km/h. The marked increase of winds recorded by HMZ AWS occurred a few hours earlier than the picking up of winds as recorded by Cheung Chau AWS. Such "early alert" from HMZ AWS was particularly useful in evaluating the impacts of Vicente on Hong Kong (Figure 2).

Figure 2

Figure 2      Time series of 10-minute mean wind speed recorded by Huangmao Zhou and Cheung Chau automatic weather stations on 23-24 July 2012 during the passage of Severe Typhoon Vicente.

HMZ AWS was the first HKO's AWS using solar energy to power its operation. Those hardware and software installed for HMZ AWS brought excellent notion in our future design and installation of subsequent AWS[6]. The operation of HMZ AWS was further enhanced successively (Table 1). HMZ AWS played a vital role in the course of development, operation, optimization and expansion of HKO's AWS observation network. Special thanks go to all the past and present HKO's equipment maintenance colleagues who contributed their dedicated efforts to maintain the operation of HMZ AWS for the continual safeguarding of Hong Kong (Figure 3).

Table 1

Figure 3

Figure 3      The staff of the Hong Kong Observatory and the Guangdong Meteorological Bureau carried out a maintenance visit to the Huangmao Zhou automatic weather station in 1987.

Chan Ying-wa


[1] Baidu Baike:

[2] Yeung, K.H., K.K. Ng and L.K. Yau, 1987: "A Solar-powered Automatic Weather Station", Technical Note No. 75, Hong Kong Observatory.

[3] Lui, W.H., 2013: "Historical Weather Observations in Hong Kong", Under the Same Sky, Weather the Storms Series, 268-275.

[4] Lawrence, W.C. Lai, 2011: "The ideas of Ronald H. Coase - Market failure and planning by contract for sustainable development", Routledge Studies in the History of Economics, Taylor & Francis Group, 95-101.

[5] Hong Kong Observatory, 2012: "Tropical Cyclones in 2012", 65-83.

[6] Lam, H.K., 2013: "Observatory Now and Then - 天文台點滴", Under the Same Sky, Weather the Storms Series, 103-112.

Last revision date: <07 Mar 2016>