Instructions to the Marine Meteorological Observers, 7th Edition. Item Type Book Publisher Government Printing Office Download date 07/10/2021 01:29:27 Item License http://www.oceandocs.org/license Link to Item http://hdl.handle.net/1834/5239 B. No. Issued June W. 1221 1941 / U. S.�EPARTMENT. OF COMMERC� ' (I WEATHER BUREAU . + Instructions to Marine Meteorological Observers + Ve 933 CIRCULAR M J Seventh Edition (51- no, M 7�1{1 F�-J lCJUJ; .' . UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1941 For oale by the Superintendent of Document., Wuhln�n, D. • • • • • • • Price 2� C. canto. Blank page retained for pagination CONTENTS Palrl! n appreciation ___________________________________________ _ A VI I. The ocean weather service ____ ------_______________ ------_____ 1 II. General Information for the marine observer_____ _______________ 2 Arrangements for reporting ________________________________ _ 2 Instruments---------------------------------------------­ 3 Forwarding reports by maiL-------------------------------- 3 3 Pilot charts______________________________________________ _ "Weather on the Oceans" _____- _______ -____ -- _____ -- _____ -- 4 4 Location of Weather Bureau offices_________________________ _ Condensed instructions for taking and recording observations 4 (French, German, Italian, Dutch, and Japanese)_ __________ _ Ill. Instruments and instrumental observations---------------------- 9 9 Mercurial barometers _____ ------- _____________ -----_______ _ 9 Mercurial barometers of marine type___ _________________ _ Explanation of scale of marine barometer_ _______________ _ 11 Errors of mercurial barometers_________________________ _ 11 Location of the mercurial barometer ____________________ _ 12 The principle of the vernier and the method of reading it_._ 13 15 Correction and reduction of barometer readings __________ _ 16 Aneroid barometers__________________ ------ _______________ . 17 Effectsof temperature ________________________________ _ Aneroid barographs------------------------------------ 17 Reading of aneroid barometers __________ --_______ ---- ___ 18 Defects in aneroids ______------ _______________________ _ 18 19 Compensation for temperature _________________________ _ 20 Measures for remedying defects ___---- __________------_- Testing of aneroids ______________ ---- ________ __ -______ _ 20 ______________________ 21 Replacement of defective aneroids _ 2 Barometer comparisons____ _________________________ --____ -_ 2 _ 23 Lack of agreement in the observations___ _______-- _____ - 23 Frequency of comparisons _________ --- _________________ - Change in barometers____________ ---- __ ---____ ------_-- 24 Thermometers ___________ ------__________________________ _ 24 24 Use of thermometers in meteorological observations___ ____ _ 25 Exposure of thermometers ____________________________ -_ 26 The aspiration thermometer _____________ -____________ -- Psychrometers-------------------------------------------- 26 27 The sling psychrometer______ -_________________________- Bucket and intake methods of obtaining ocean surface tempera- tures----------------------·---------------------------- 29 30 IV. Instructions for takingand recording weather observations_______ _ 31 Notes on instruments used__ ______ ---____ -----_--------- Tim d o 32 lD�� � ���th��====================�================== 32 32 Local ship's time ______ -------- ________________ -------- 32 Day of week ______________ ---___-- ---- ---------------- 33 Octant of globe____ ________ ----------_-_--------------- 33 Latitude and longitude___________ -- _____ --- ---------- -- 34 Greenwich civil time________ ___________ - ---------- ---- VVind--------------------------------------------------" -- 34 34 Wind direction______ ------ ______ -----__ -- - - -- - -------- _ _ 35 Wind force _________________________________________ The apparent and the true direction and force of the wind-- 37 38 Weather__ _______ ·-------------· -------------------------- Explanatory remarks on the code table for "present weather" 41 and instructions for its use______ -· ---- -- -------------- 111 IV CONTENTS IV. Instructions for taking and recording weather observations-Con. l'age 44 Barometric pressure_____ __________________ ________________ _ Attached thermometer ________ _____________ __________ __ 45 Barometer corrected___ ______ _____________ ____________ _ 45 Barometer as coded ________ ____________ __ _____________ _ 45 Visibility _______________________ __________ .. _______ ________ 47 48 Temperatures__________________________ __ ________________ _ 48 Temperature of the air__________________ . __ ___________ _ Temperature of the ocean surface______ __ __ _ ____________ _ 49 50 Temperature of the wet bulb____ ___________ _ ___________ _ 52 Clouds__________ _________________________ _______________ _ 52 Amount of clouds____ ___ - __ _________ - __ __ _____________ _ 52 Kind of clouds __ - ____________ - _____ -_______ ______- ___ _ 52 Direction of cloud movement _________________ _________ _ 53 Cloud notes in Daily JournaL___ ______ _________ _ _____ ___ 53 Sea and swelL ___________________________________ ________ _ 54 State of sea_____ - _____________________________ .. __ ____ _ 54 Character and direction of swelL ____________ ___ .. ___ . ____ li5 Period of swells___ _____________ - ____________ . _____ . ___ _ 55 Gale, storm, and fog reports __________________ _____ _ _____ _ .. _ 55 Supplemental data for radio messages____ ---- _____________ ___ 56 Barometric tendency___________________ _______________ _ Characteristic of changes of the barometer in the last 3 hour1L 57 58· Barometer change ____________________________________ _ Form of predominating cloud___ ___________________ _____ .'>8 59 Form of lower clouds_____ _______________ _______________ .')9 Form of middle clouds__ ________________ . ________ ____ .. 59 Form of upper clouds________________________ _____ __ . __ 60 Total amount of all clouds__ ________________ _______ .. ____ 69 Amount of lower clouds _____________________________ . __ 60 Temperature differencebetween air and water___ _________ _ 61 Past weather__________________ -____________ . _________ _ 61 State of sea ______________________________________ _ - .. __ 61 Character of swelL _________________________ .. ________ _ . 62 Direction from which swell is moving _______ _________ ___ _ Ship's course__ _______________ .. __ ------- __ ---__ -------- 62 62 Ship's speed _____________________________ _____________ 62 Height of base of cloud__ _______________ ________________ 62 Miscellaneous phenomena _____________ _ ____________________ 62 Observation of meteors__ ___________ __ ______________ -__ _ V. Clouds------------------------------------- ---------------- 63 64 Classificationof clouds ____________________________________ _ - __ _ 64 Definitionsand descriptions of the forms of clouds_________ 64 Cirrus___ _____________________________________________ 65 Cirrocumulus ____________________ _______________ ______ 65 Cirrostratus____ ________________________________ ______ _ Altocumulus___ _______________________________ ________ 65 ____ 67 Altostratus____ __________________________________ _ Stratocumulus-------------------�-------- ------------ 70 Stratus___ ___________________________________________ _ 70 73 Nimbostratus___________ ___ _______________ _____ ______ _ 75 Cumulus____ _________________________________________· 75 Cumulonimbus________________________ ________________ 78 Definitionsof important hydrometeors__ ______ _________ ______ 80 VI. Optical phenomena_____ _____________________________________ _ 80 Perspective phenomena____ ________________________________ _ ______________ 80 Apparent stair-step ascent of clouds_____ ___ 80 Apparent arching of cloud bands _______________________ _ 80 Apparent divergence and convergence of crepuscular rays __ 81 Refraction phenomena _______________ _____________________ _ 81 Shadow bands___ ____________________ _________ ________ _ 81 Terrestrial scintillation _______ __________________________ Shimmering__________________________ _______ __________ 81 81 Opticalhaze ________________________________________ _ 82 Greenfiash__ ________________________________________ _ 82 Terrestrial refraction ___________ ________________________ 82 Lootning--------------------------------------------- CONTENTS V VI. Optical phenomena-Continued. Refraction phenomena--Continued. Page 82 Towering _______ ____________________ ____ _____________ _ 82 Sinking _____________________________ __________________ 82 Stooping ____________________________________________ _ 82 Refraction by water drops_- ___ --_________ --_- ---______ -·- __ _ 82 Rainbow__ _______________________ ____________ ________ 83 Refraction by ice crystals__ -_---- __ ----_--- ------ __________ _ 84 Parhelia of 22° _______________________________________ _ 84 Halo of 22° __________- __- ---- ----_ ----__ -- -_____ -___ - _ 85 Arcs of Lowitz ___ __ -- __--- _-----_----_- ---_____ - .. __ -- 85 Parhelia of 46°- ___________________________ ________ _ 85 Halo of 46 ° and 90° _______________________________ _ Circumzenithal and circumhorizontal arcs _____ .. ______ 86 86 Tangent arcs ______________________________ _____ ___ 86 Unusual halos____ -____ - ___ -_-_-_ --___-- ___ -_-____ _ 87 Diffractionphenomena ____________ ____________ _________ 87 Coronas________________________ _____ ___ _________ _ 87 Iridescent clouds _________________ .. _____ .. __________ Mirage___ - ___ --___ -- --- -·--- --------- --- -------- --- 87 Au o a s