gg INSTRUCTIONS TO MARINE METEOROLOGICAL OBSERVERS 



BUzzurd. — A violent, intensely cold wind, hideu with snow. 



Bright segment. — The hroad liand of golden light fhut. in clear weather, 

 borders the western Iiorizon jnst after sunset and the eastern just before 

 sunrise. 



Buys Ballot's lan\ — In the Northern Hemisphere, if yon face the wind the 

 atmospheric pressure decreases toward your right and increases toward your 

 left. In the Southern Hemisphere the reverse is tine. The law is useful in 

 locating centers of cyclones and anticylones. 



Calibration. — The name ordinarily given to the process of ascertaining the 

 corrections to be applied to the indicated readings of an instnnnent in order 

 to obtain true values. 



Calm. — Absence of appreciable wind. 



Calms of Cancer: calms of Capricorn. — The belts of high pressiu'e lying 

 north of the northeast trade winds and sonth of the southeast trade winds, 

 respectively. 



Cascade. — The name applied to the mass of spray or dense vapor thrown 

 outward from around the base of a water.spout. Also known as "bush", or 

 "l)ontire." 



Center of action. — Any one of several large areas of high and low barometric 

 pressure, changing little in Incation, and persisting through a season or 

 through the whole year: e. g., the Iceland low, the Siberian winter high, etc. 

 Changes in the intensity and positions of these pressure systems are asso- 

 ciated with widespread weather changes. 



Ce-ntihar. — (See I>ar. ) 



Centigrade. — A thermometric scale on which 0° denotes the temperature of 

 melting ice, and 100° the temp(>rature of boiling water, both under standard 

 atmospheric pressure. 



Chinool:. or chinool: irind. — A foehn blowing down the eastern slopes of the 

 Rocky Mountains over the adjacent plains, in the United States and Canada. 

 In winter, this warm, dry wind causes snow to disappear with remarkable 

 rapidity, and hence it has been nicknamed the "snow-eater" (Cf. Foehn). 



Circiimscrihcd halo. — A halo formed by the junction of the upper and lower 

 tangent arcs of the halo of 22°, when the luminary is al)out 40° or more above 

 the horizon. As the altitude of the luminary increases, the circumscribed 

 halo gradiially assumes an elliptical form and finallv merges into the halo 

 of 22°. 



Circum zenithal are. — A rainbow-tinted halo, often very bright, convex to the 

 luminary, and 46° or a little more above it. It is sometimes called the upper 

 quasi-tangent arc of the halo of 46°, biit the circinnzenithal arc and the halo 

 of 46° are rarely seen at the same time. 



CirrociimuUis. — A form of cloud. (See part Y. ) 



Cirrostratus. — A form of cloud. (See part V.) 



Cirrus. — A form of cloud. (See part V.) 



Climate. — The prevalent or characteristic meteorological conditions of any 

 place or region. 



Climafolotfii. — The stiuly of climate. 



Cloud hanner. — A banner-like cloud streaming off from a mountain peak. 



Clond-hur-^t. — A sudden and extremely heavy downpour of rain ; especially in 

 mountainous regions. 



Cloud cap. — A cap-like cloud crowning (1) a mountain summit, or (2) 

 another cloud, especially a mass of cumulonimbus. 



Col. — A neck of relatively low pressure between two anticyclones ; also called 

 a saddle. 



Cold air mass. — Rroadly speaking, an air mass that is cold relative to 

 neighboring air mas.ses. The term imi)lies that the air mass originated in 

 higher latitudes than those in which it now linds itself and that it is, there- 

 fore, colder that the surface over which it is moving. 



Cold front. — The discontinuity at the forward edge of an advancing cold air 

 mass which is displacing warmer air in its path. 



Cold wave.- — A rapid and marked fall of temperature during the cold season 

 of the year. The United States Weather Bureau applies this term to a fall of 

 temperature in 24 hours ecpialing or exceeding a specified number of degrees 

 and reaching a specified minimum temperature or lower; the specifications 

 varying for different parts of tlie country and for different periods of the 

 year. 



