IV CONTENTS 



IV. Instructions for taking and recording weather observations- — Con. rage 



Barometric pressure 45 



Attached thermometer 45 



Barometer corrected 45 



Barometer as coded 45 



Visibihty 47 



Temperatures 48 



Temperature of the air 48 



Temperature of the ocean surface 49 



Temperature of the wet bulb 50 



Clouds 52 



Amount of clouds 52 



Kind of clouds 52 



Direction of cloud movement 52 



Cloud notes in Daily Journal 53 



Sea and swell 53 



State of sea 54 



Character and direction of swell 54 



Period of swells 55 



Gale, storm, and fog reports 55 



Supplemental data for radio messages 55 



Barometric tendency 56 



Characteristic of changes of the barometer in the last 3 



hours 57 



Barometer change 57 



Form of predominating cloud 58 



Form of lower clouds 59 



Form of middle clouds 59 



Form of upper clouds -- 59 



Total amount of all clouds 60 



Amount of lower clouds 60 



Temperature difference between air and water 60 



Past weather 61 



State of sea 61 



Character of swell 61 



Direction from which swell is moving 61 



Ship's course 61 



Ship's speed 62 



Miscellaneous phenomena 62 



Observation of meteors 62 



V. Clouds 63 



Classification of clouds 63 



Definitions and descriptions of the forms of clouds 64 



Cirrus 64 



Cirrocumulus 65 



Cirrostratus 66 



Altocumulus 66 



Altostratus 68 



Stratocumulus 70 



Stratus 72 



Nimbostratus 74 



Cumulus 75 



Cumulonimbus 75 



Definitions of important hydrometeors 78 



VI. Optical phenomena 79 



Perspective phenomena 80 



Apparent stair-step ascent of clouds 80 



Apparent arching of cloud bands 80 



Apparent divergence and convergence of crepuscular rays_ 80 



Refraction phenoinena 80 



Shadow bands 81 



Terrestrial scintillation 81 



Shimmering 81 



Optical haze 81 



Green flash 81 



Terrestrial refraction 81 



Looming 82 



