HKMetS BULLETIN, Volume 1, Number " 1991 HONG KONG METEOROLOGICAL SOCIETY About the cover The cover picture shows a G.M.S. colour enhanced picture of Typhoon Yancy around noon on 18th August, 1990, the hottest day ever recorded in Hong Kong The Hong Kong Meteorological Society EDITOR-in-CHIEP Bulletin is the official organ of the Society. devoted to editorials, news, Bill Kyle articles, activities and announce­ ments of the Society. EDITORIAL BOARD Members are encouraged to send art­ cles, media items or information for Johnny C.L. Chan publication in the Bulletin. For guid­ Edwin S.T. Lai ance please see "INFORMATION Andrew Lockert FOR CONTRIBUTORS" in the inside Glenn McGregor back cover. The Bulletin is copyright. Penniss­ Views expressed in articles or ion to use figures, tables, and brief correspondence are those of extracts from this publication in of the writers and do not necess­ scientific and educational work is represent those of the Society. hereby granted provided that the The mention of specific products source is properly acknowledged. or companies does not imply Any other use of material requires endorsement by the Hong Kong the written permission of the Hong Meteorological Society in pref­ Kong Meteorological Society. erence to others which are not mentioned. Published by ~ The Hong Kong Meteorological Society c/o Royal Observatory, 134A Nathan Road, Kowloon, Hong Kong. HKMetS BULLETIN, Vol. 7, Number 7, 7997 HONG KONG METEOROLOGICAL SOCIETY BULLETIN CONTENTS Editorial 2 Research in the atmospheric sciences in Hong Kong - a proposed agenda 3 Johnny c.L. Chan "SPECTRUM" : typhoons under critical examination 7 c.Y. Lam Storm period variation of rainfall pH: the example of Typhoon Brenda, May 1989 10 Mervyn R. Peart An analysis of tide gauge and storm surge data in Hong Kong 16 Wyss W.S. Yim News and Announcements 24 Correspondence 26 Hong Kong Weather Reviews 27 Meeting Reviews 36 Calendar of Coming Events 41 Editorial On the special occasion of the inaugural issue 4 Society. With this in mind an Editorial Board the Hong Kong Meteorological Society Bulletin the Editori­ was formed and after a considerable gestation al Board has invited Mr. P. Sham, foun ding Chairman of period produced the "new baby" which you are the Hong Kong Meteorological Society, to write this first now holding. Editorial. As founding Chairman of the Society it gives me great pleasure to write this inaugural Editorial. A glance at the contents page of this first issue will provide you with a good idea of the range of material which the Editorial Any new venture, whether it be a new Board hopes to include in forthcoming issues of job, a move to a new home, or even a new the Bulletin. The publication of articles which hobby presents opportunities as well as risks. serve to inform members of progress being The satisfaction which one derives from suc­ made in the profession is clearly of great cessful p art ic ip at ion in such ventures often importance but the capability to act as a forum stems from the way in which we handle these for members views and as a vehicle for news two complementary attributes. You are now and reviews of Society activities is also seen to reading the first issue of the latest venture by be of considerable value. the Hong Kong Meteorological Society. The level of satisfaction which you express with the The Editorial Board recognizes, finished product will be a measure of how however. that not all our members are profes­ successfully the Editorial Board has balanced sional meteorologists and so they need to ascer­ the opportunities and risks associated with its tain what your interests and needs are. They production. are aware that a reader's trust and respect must be earned and fully intend to do their The Society itself is a new venture. part. You can help them by turning the rela­ being registered in accordance with the provi­ tionship into a dialogue. Let them know what sions of Section 5 of the Societies Ordinance you think of the Bulletin, what you want most just over two years ago, and holding its inau­ to see on our pages. Like you, they are eager gural meeting in March 1989. It has had to listen and learn, to make each issue better moderate success in its first two years of exist­ and more responsive to the needs and aspira­ ence with the growth in membership being tions of members than the previous one. better than expected. The Executive Commit­ tee feels that this has been achieved by sustain­ I hope that you find this first issue of ing the interests of members by the variety of the Bulletin interesting and informative and, activities organized throughout the year. through your continued support. the harbinger These have included a Special Topics Lecture of many successful issues to come. Series, three Research Forums , and a Puhl ic Lecture Series. However, it has been felt for some time that it was essential for the Society • to publish a regular magazine devoted to news. - articles, activities and announcements of the Mr. P. Sham. Chairman 2 flKMeJS BULLETIN Vol. I, No. I, 1991 Johnny C.L. Chan Department ofApplied Science City Polytechnic ofHong Kong Research in the atmospheric sciences in Hong Kong - a proposed agenda ing on research problems related to atmospheric science. Introduction This paper discusses a number of impor­ tant topics in atmospheric science wh ich are Research in the atmospheric sciences in Hong likely to be of interest to local scientists and Kong probably started towards the end of the last proposes the type of research that could be car­ century after the Royal Observatory (RO) was ried out. It is hoped that such discussion can established (Royal Observatory, 1989). Although generate more ideas so that research in the some occasional collaboration does take place atmospheric sciences in Hong Kong can continue between the RO and local or overseas institutes, to grow and eventually become respectable in the most of the research has been performed at the international community. RO. This situation has arisen because local ter­ tiary institutes do not have departments special iz­ Hong Kong, situated near the Tropic of ing in atmospheric science. This is a conse­ Cancer, is intluenced by weather both from the quence of the fact that the RO has been the only tropics and the mid-latitudes. Research in place where such graduates could go but its weather phenomena affecting Hong Kong yearly intake of these graduates was too small should therefore he divided into these two to justify setting up departments with this categories. However, such a division is not so special ity. clear-cut at times. For example, the severity of a cold surge can be influenced by the approach of a However, the situation has heen slowly typhoon te.g.. Chan. 1988a) while the track of a changing during the last few years. Concerns typhoon can also he modified by a cold surge over the environment and cl imatic change have (e.g., Chan, 1988h). Therefore, in the following led to increased research in these areas in the sections, the issues are grouped according to the tertiary institutes by scientists of related disci­ time scales of the weather phenomena. The first plines. Consultant companies dealing with envi­ section discusses the problem of nowcasting. The ronmental problems have also mushroomed. applicability of current numerical-weather-predic­ Graduates with knowledge in atmospheric or tion (NWP) models to medium-range forecasting environmental sciences can find employment in is then addressed. Because of their overwhelm­ these companies or even form their own! ing importance to Hong Kong, tropical cyclones Academic departments which provide training in are separately discussed in the section after that. these areas are also being set up in some local The hot topic of long-range weather forecasting tertiary institutes. At the same time, conservative and climatic change is discussed next and finally, budgeting by the government has limited the a summary is presented. amount of resources available for its departments to carry out research and development work. Thus, research in the atmospheric sciences in Nowcasting Hong Kong appears to be taking on a new dimen­ sion. Cooperative research projects hetween the RO (and possibly other government departments) Nowcasting (or sometimes referred to as very­ and local tertiary institutes are on the increase. short-range forecasting) is usually defined as More scientists in these institutes are also work- forecasting of weather with a time-scale of 0 to 6 JJKMelS BULLETIN, Vol. 1, No.1, 1991 3 hours. Tropical convective systems can be con­ (Chan, 1989) or global numerical models (Chan, sidered as the most important phenomenon in this 1988a). While improvements on the regional category as far as Hong Kong is concerned. model of the RO continue to be made (Chan, These systems, which have spatial scales of 20 to 1989), the performance of these regional and 200 km (the meso-beta scale as defined by Orlan­ global models under different situations should be ski, 1975), can develop within a couple of hours analyzed. That is, questions such as "when and produce copious amounts of rain due to the should I believe the predictions from this model" high mixing ratio of the tropical atmosphere. need to be answered. Methods to predict the Mesoscale convective elements developed within forecasting skill of numerical models have been rainbands of tropical cyclones also fall in this developed (e.g., Leslie and Holland, 1990) and category. could be appl ied , This type of research is not necessarily of a purely operational nature. To be able to predict the development Analyses of the model performance can provide of these meso-beta convective systems, one clues as to how a model can be improved.