BÀI GIẢNG KHÍ TƯỢNG THỰC HÀNH CHƯƠNG 11 12

CHAPTER 11 Observation of Ice Accretion CHAPTER 11 Observation of Ice Accretion Ice accretion (icing) is the growth in size, particularly by accumulation, of ice formed on the ship's exposed surfaces Ice accretion is extremely hazardous in its effects on ships, particularly on vessels of less than 1,000 gross tonnage On ships of the order of 10,000 gross tonnage it can cause radio and radar failures due to the icing of aerials Visibility from the bridge may also be affected Troubles tend to arise due to icing on the deck cargoes of large container ships Apart from its possible effect on stability it may cause difficulty in unloading cargo at the port of destination when containers and their lashings are frozen solidly to the deck 11.1 Ice accretion on ship There are three main types of ice accretion depending on causes: 1) Ice accretion due to spray and sea water thrown up by the interaction between the ship and the waves, and/ or due to spray blown from the crests of the waves 2) Ice accretion due to freezing rain, drizzle or fog 3) Ice accretion due to wet snow followed by a drop in temperature Two or all of these types may occur simultaneously The type 1) is the most concerned for the ship More detailed classification is required to be reported According to studies on the meteorological effects on ice accretion in the western North Pacific, general features are summarized as follows: If the sea surface temperature is under 4't, ice accretion starts when the air temperature drops to - 3°C and the wind speed increases to m/ s Strong ice accretion with growth rate of more than cm/hour takes place for further lower temperature (less than - 6°C) and larger wind speed (more than 10m/s) If the sea surface temperature is less than 2°C, ice accretion starts for the air temperature less than - 2't The general relation among air temperature, wind speed and characteristics of ice accretion is shown by Fig.11.1 One should remind however that with the air temperature under -l7't, spray freezes before it is thrown up on the ship and therefore the growth rate of ice accretion slows down If you are navigating in the area where the sea surface temperature is under 4°C and low air temperature and strong wind are expected, you should be careful of the possibility of disasters caused by ice accretion on ship 73 CHAPTER 12 CHAPTER 12 Port Meteorological Officer (PMO) Port Meteorological Officer (PMO) The Port Meteorological Officer (PMO) is defined by WMO as the official of the Meteorological Service of a WMO Member who is stationed at a main seaport with the tasks of maintaining liaison with weather observers on board ships, checking instruments, providing advice, and contacting shipping authorities to enlist their cooperation in operating mobile ship stations (weather station aboard a moving ship) The PMO visits ships to encourage them to report weather and offers the following services free of charge: - To check and calibrate instruments equipped on ships including barometers and to give necessary advices - To provide instruction or assistance with regard to questions or inquiries on meteorology or oceanography, specifically on marine meteorological observation and its reporting - To explain such materials published by JMA as Marine Meteorological Logbook, Guide to Weather Observation for Ships, Ship's Weather Code Card, etc If requested, the PMO supplies necessary copies - To inform the schedule of radio facsimile transmission from the meteorological services for ships and explain how to receive and utilize it There are three PMOs in Japan as shown below They are in Yokohama, Nagoya and Kobe You can also receive similar services from marine observatories in Hakodate, Maizuru and Nagasaki Note that the following E-mail address is common to all officers/ offices Port Meteorological Officers Port Meteorological Officer, Yokohama Local Meteorological Observatory 99, Yamate-cho, Naka-ku, Yokohama, 231-0862JAPAN fax: +81-45-622-3520, E-mail: pmo@climar.kishou.go.jp Port Meteorological Officer, Nagoya Local Meteorological Observatory 2-18, Hiyori-cho, Chikusa-ku, Nagoya, 464 -0039 JAPAN fax: +81-52-762-1242, E-mail: pmo@climar.kishou.go.jp Port Meteorological Officer, Kobe Marine Observatory 1-4-3 Wakinohamakaigan-Dori, Chuo-ku, Kobe, 651-0073 JAPAN fax: +81-78-222-8946, E-mail: pmo@climar.kishou.go.jp Other Port Meteorological Service Offices Maritime Meteorological Division, Hakodate Marine Observatory 3-4-4, Mihara, Hakodate, 041 -0806 JAPAN fax: +81-138-47-7682, E-mail: pmo@climar.kishou.go.ip 75 CHAPTER 12 Port Meteorological Officer (PMO) Maritime Meteorological Division, Maizuru Marine Observatory 901, Shimofukui, Maizuru, 624 -0946 JAPAN fax: +81-773-76-4114, E-mail: pmo@climar.kishou.go.jp Maritime Meteorological Division, Nagasaki Marine Observatory 11-51, Minamiyamate, Nagasaki, 850-0931 JAPAN fax: +81-95-823-8220, E-mail: pmo@climar.kishou.go.jp Headquarters Marine Division, Climate and Marine Department, Japan Meteorological Agency 1-3-4, Otemachi, Chiyoda-ku, Tokyo, 100-8122JAPAN fax: +81-3-3211-6908, E-mail: pmo@climar.kishou.go.jp To maintain the accuracy of barometer for meteorological observations, it should be checked every six months H it is not possible for your ship to visit the above Japanese ports for a long time, you can also have your barometer checked by the following ways; 1) H your ship will call at a foreign port in which a PMO is stationed, you can receive a PMO service there regardless of flag 2) In Japanese ports other than the above, you can have your barometer checked using facsimile on request Please contact one of the Japanese PMOs for details 76 Appendix The list of supplies for ship's weather observations and reports -Al- The JMA provides VOSs with the following materials free of charge: Guide and tables for weather observation Guide to Weather Observations for Ships Guide to Ships' Weather Reports Ships' Weather Code Card Table for Finding the Dew-point Temperature JMA Cloud Plate Beaufort Scale of Wind Force Materials for making weather observation reports OBSJMA (Software on CD-ROM) and empty disks for storing the data Operation Manual for OBSJMA Ship's Weather Observation Field Note for OBSJMA Marine Meteorological Logbook Envelope to send logbooks or floppy disks (postage free within Japan) Brochure Marine Meteorological Observations and the Services of Port Meteorological Officers Guide to Wave Chart Marine Meteorological Information Services for Shipping and Fishing Bulletin The Ship and Maritime Meteorology Appendix Table for saturated vapor pressure -A3-