HKMetS BULLETIN, Volume 5, Number 1, 1995 HONG KONG METEOROLOGICAL SOCIETY ISSN 1024-4468 ISSN 1024-4468 About the cover The cover picture shows an aerial view of The Royal Observatory Hong Kong's Tate's Cairn radar station overlooking Kowloon to the southwest. The radome on the left houses the Digital Weather Weather Radar installed in 1983 and the subject of an article by S.K. Wong and K.L. Ho in HKMetS Bulletin \.Vi. 4, No.2. The Doppler Weather Radar is housed in the protective radome on the left. See the article by B.Y. Lee, O. Wong, C.M. Cheng, S.C. Tai & Y.S. Hung in this issue for more details. The Hong Kong Meteorological Society The Bulletin is copyright material. EDITOR-in-CHIEF Bulletin is the official organ of the Society, devoted to editorials, articles, Bill Kyle news, activities and announcements of Views expressed in the articles or any the Society. correspondence are those of the authors alone and do not necessarily represent EDITORIAL BOARD those of the Society. I Members are encouraged to send any Johnny c.i: Chan articles, media items or information for Y.K. Chan publication in the Bulletin. Permission to use figures, tables, and wz, Chang brief extracts from this publication in Edwin S.T. Lai For guidance see the "INFORMATION any scientific and educational work is FOR CONTRmUTORS" in the inside hereby granted provided that the source back cover. is properly acknowledged. Any other SUBSCRIPTION RATES use of the material requires the prior written permission of the Hong Kong Two issues per volume. Advertisements for products and/or Meteorological Society. services of interest to members of the Institutional rate: Society are accepted for publication in the Bulletin. The mention of specific products and/or HK$ 300 per volume. companies does not imply there is any For information on formats and rates endorsement by the Society or its office Individual rate: please contact the Society Secretary at bearers in preference to others which the address below. are not so mentioned. HK$ 150 per volume. Published by ~'6 - ~'r', "\ ~- - -, The Hong Kong Meteorological Society C!f) Royal Observatory, 134A Nathan Road, Kowloon, Hong Kong. HKMetS BULLETIN, Vol. 5. Number 1, 1995 HONG KONG METEOROLOGICAL SOCIETY BULLETIN CONTENTS Editorial 2 On An Apparent Connection of the Electrical 3 Conductivity of Rainwater with Severe Storms and Urban Activity in Hong Kong Ronald Sequeira 1994 Tropical Cyclone Summary for the 16 Western North Pacific Ocean Bill Kyle Hong Kong's New Doppler Weather Radar 33 RY Lee, O. Wong, C.M. Cheng, S.C. Tai & YS. Hung United Nations Climate Change Bulletin 45 Issue 6: 1st Quarter, 1995 News and Announcements 54 Hong Kong Weather Reviews 73 Meeting Reviews 78 Calendar of Coming Events 80 ---------------------------JI Editorial This issue of the Bulletin contains three papers on The next section of this Bulletin provides our widely varying aspects of the atmospheric readers, as in the previous Bulletin, with the environment in Hong Kong. latest issue, Number 6 of The United Nations Climate Change Bulletin. This organ is The first paper, by Ronald Sequeira of the City published quarterly (Issue 6 in 1st quarter 1995) University of Hong Kong, investigates the by the interim secretariat for the UN Climate relationships between the chemical properties of Change Convention, the Secretariat of the rainwater collected at a rural site in the New UNEP/WMO Intergovernmental Panel on Territories and the prevailing meteorological and Climate Change (IPCC) and the UNEPIWMO human activities taking place. In it he draws Information Unit on Climate Change (IUCe). It attention to an apparent connection between the provides articles and information of a general quality of rainwater and the prevailing meteoro­ nature concerning the subject of climate change. logical conditions which gives rise to the rainfall and links this, not only to variations in The remainder of the Bulletin contains the atmospheric conditions, but also to the associated regular features News and Announcements, changes in human activity which take place Hong Kong Weather Reviews, Meeting Reviews in response to those conditions. While the and Calendar of Coming Events. The News connection may indeed prove to be apparent, as and Announcements section contains much useful implied by the title, this paper is certain to raise information including the 1995 Atlantic Hurricane new questions which should provide an impetus Season and Sahel Rainfall forecasts made by for further investigation. Colorado State University meteorologists. Hong Kong Weather Reviews focusses on Autumn The second paper continues the annual review of 1994 and Winter 1994-95 in Hong Kong, tropical cyclone activity in the Western North providing an overview of the season and a more Pacific Ocean started in Bulletin Vol.3 No.1. As detailed monthly summary of weather events. in previous issues, the paper documents all storms occurring in the region providing information The Editorial Board expresses their thanks to the about tracks, changing weather conditions and contributors and hope that you, the reader, find resulting impacts on the areas affected. Special this issue useful and informative. We welcome emphasis is also placed on those storms affecting all comments and suggestions for items to be Hong Kong. included as well as news and contributions of articles related to your own activities. The third paper may be considered a follow-up to that by S.K. Wong and K. L. Ho of the Royal Ob~ervator~, Hong Kong (Bulletin VoLA No.2) which provided a brief history of the weather radars used by the Royal Observatory for the last 35 years. In this new paper, B.Y. Lee and his colleagues document the new Doppler Weather Radar recently installed at the Tate's Cairn facility, focussing on the capabilities of the system and the potential advantages for forecast­ Bill Kyle, Editor-in-chief ing as this new data is now available. 2 HKMetS BULLETIN Vol. 5, No.1, 1995 Ronald Sequeira Department of Biology and Chemistry City University of Hong Kong On an Apparent Connection ofthe Electrical Conductivity of Rainwater with Severe Storms and Urban Activity in Hong Kong ABSTRACT about two decades now (NOAA-WMO-EPA) with very few attempts to explain its measured Results of the analysis of seventeen daily, bulk value on the basis of the observed ionic composi­ rainfall samples from an elevated, vegetated, tion, the notable exceptions being studies on U.S. rural area in Hong Kong during the summer of precipitation with ionic strength predominantly 1993 are presented. The balance between the below 0.1 mM (Miles and Yost, 1982), and a total inorganic cations and anions was satisfactory regression analysis of Alpine snow chemistry to excellent, with a single exception. However, data (Puxbaum et al., 1991). the electrical conductivity calculated on the basis of the assumption that the rain samples are A study of event type of samples in Venice infinitely dilute only accounts for 34 to 80 percent (Argese and Bianchini, 1989) appears to suggest of the experimentally measured value for thirteen that filtration of even wet-only deposition is of the samples. A significant observation is that necessary for the approximate agreement between the inorganic composition of the remaining four the calculated and measured conductivities, A K samples accounts, within experimental error, for and A ,respectively. The above authors, In the measured conductivity. It is observed that however, also speculate that the unfiltered sam­ these rainfall episodes are associated with the ples show changes in conductivity with time (days influence on the territory of major tropical to several weeks) because of the slow dissolution storms, and in one case, with the period that of mineral constituents from soil particles in the immediately followed the passage of one such water with a simultaneous disappearance of the storm. H+ ion. However. the L1 H values given in data presented in Table 1 of their paper apparently It is tentatively suggested that bulk rainwater at disagree (often with respect to the sign, let alone the rural site is normally affected by charged the magnitude) with the Ll A for almost all particles of anthropogenic origin not included in data sets presented, thus len1aing very little the list of the analyzed inorganic ions, and there­ support to their tentative explanation. fore, probably largely organic. The direct impact of storms virtually clears the urban air of such In the present paper, the chemical composition of particles. This is believed to be due partly to the seventeen, unfiltered, bulk daily rainwater arrival of the maritime (unpolluted air) which samples collected at a rural location, Kadoorie flushes out the urban air, and partly due to the Agricultural Research Centre (KARC), Shek hoisting of the severe storm signal (#8 or higher) Kong, New Territories, Hong Kong during the which brings the usually hectic urban activities in summer of 1993 are presented. The samples the territory to a virtual halt. were collected during a variety of rainfall event situations associated with troughs and tropical Introduction cyclone activity. The station (Figure 1) is suitable as an urban background site for Hong Kong since Rainwater is often considered to be a dilute it has no localized sources of air pollution. The aqueous solution to which the Kohlrausch law measured electrical conductivity,, A m is of the independent migration of ions (Barrow, compared with that calculated from the inorganic 1979) should, in principle, be applicable. Indeed, ionic composition determined analytically, A K' The anion-to-cation ratio ( R i.e. L - / L +) and the electrical conductivity of rainwater has been 1 reported for numerous locations in the world for the pH variation are also presented. HKMetS BULLETIN Vol. 5, No.1, 1995 3 '.\:, 40N 30 t KARC 20 (J t1 p (), L--L......J---.l--..!~--'1,0 km 0 Figure 1.