HARMONIC PREDICTION 



harmonic prediction — The method of predicting 

 tides and tidal currents by combining the 

 harmonic constituents into a single tide curve. 

 (50) 



harmonic reduction — See harmonic analysis. 



harmonic synthesizer — A machine, such as the 

 tide-predicting machine, which combines the 

 elementary harmonic constituents into a single 

 periodic function. See tide-predicting ma- 

 chine. (50) 



harmonic tide plane — Indian spring low water. 



haul — (or tow^ . A single tow of a net. 



haycock — An isolated conical pile of ice thrown 

 up a;bove the surface of land ice or shelf ice, 

 resulting from pressure or ice movement. (68) 

 Rare. 



haze — Fine dust or salt particles dispersed through 

 a portion of the atmosphere; a type of litho- 

 meteor. The particles are so small that they 

 cannot be felt or individually seen with the 

 naked eye, but they diminish horizontal visibil- 

 ity and give the atmosphere a characteristic 

 opalescent appearance that subdues all colors. 

 (5) 



head — 1. In hydraulics, the vertical distance be- 

 tween the surface of a liquid and another point 

 in the column; thus, a measure of the force 

 exerted at the lower point by the weight of the 

 column. 



2. That part of a rip current that has 

 widened out seaward of the breakers. (61) 

 {See figure for nearshore current system.) 



3. A precipitous cape or promontory extend- 

 ing into a large body of water. See headland. 



heading — The direction toward which a ship is 

 oriented. A heading is often designated as true, 

 magnetic, compass, or grid north, respectively. 



headland — (or head, promontory, naze, ness). A 

 high, steep-faced promontory extending into 

 the sea. Usually called head when coupled with 

 a specific name. 



head sea — See beam sea. 



head tide — See beam tide. 



head wind — See crosswind. 



heart urchin — See sea urchin. 



heat — (sometimes called thermal energy). A 

 form of energy transferred between systems by 

 virtue of a difference in temperature, and exist- 

 ing only in the process of energy transformation. 

 By the first law of thermodynamics, the heat 

 absorbed by a system may be used by the system 

 to do work or to raise its internal energy. (5) 



heat balance — 1. The equilibrium which exists on 

 the average between the radiation received by 

 the earth and atmosphere from the sun and that 

 emitted by the earth and atmosphere. 



That the equilibrium does exist in the mean 

 is demonstrated by the observed long term con- 

 stancy of the earth's surface temperature. On 



the average, regions of the earth nearer the 

 Equator than about 35° latitude receive more 

 energy from the sun than they are able to radi- 

 ate, while latitudes higher than 35° receive less. 

 The excess of heat is carried from low latitudes 

 to higher latitudes by atmospheric and oceanic 

 circulations, and is reradiated there. 



2. The equilibrium which is known to exist 

 when all sources of heat gain and loss for a 

 given region or body are accounted for. In 

 general this balance includes advection, evap- 

 oration, etc., as well as radiation. 

 (5) 



heat budget — The accounting for the total 

 amount of the sun's heat received on the earth 

 during any one year as being exactly equal the 

 total amount which is lost from the earth by 

 reflection and radiation into space. The por- 

 tion reflected by the atmosphere does not affect 

 the earth's heat budget. The portion absorbed 

 must balance the long-range radiation into space 

 from the earth's entire system. That portion 

 absorbed into the oceans causes the surface 

 warming critical to the phenomenon of layer 

 depth. Transport by currents further extends 

 the distribution of heat. See heat transport. 



heat capacity — (also called thermal capacity). 

 The ratio of the heat absorbed (or released) by 

 a system to the corresponding temperature rise 

 (or fall) . If this ratio varies with temperature, 

 it must be defined as a differential dQ/dT where 

 dQ is the infinitesimal increment of heat and dT 

 the infinitesimal increment of temperature. (5) 



heat conduction — The transfer of heat from 

 one part of a body to another, or from one body 

 to another in physical contact with it without 

 displacement of the particles of the body, for ex- 

 ample, the transfer of heat by conduction 

 through the sea bottom. Since the amount is 

 very small, 50 to 80 gram calories per square 

 centimeter per year, it is neglected when con- 

 sidering the heat budget. 



heat conductivity — See thermal conductivity. 



heat equivalent of fusion — See latent heat. 



heat transport — The process by which heat is car- 

 ried past a fixed pomt or across a fixed plane; 

 thus, a warm current such as the Gulf Stream 

 represents a poleward flux of heat. 



heat trap — A temperature increase just above the 

 thermocline. A winter phenomenon due to 

 surface cooling in areas of warm water 

 advection. 



heave — 1. The motion imparted to a floating body 

 by wave action. It includes both the vertical rise 

 and fall, and the horizontal transport. 



2. The up and down motion of the center of 

 gravity of a ship. See ship motion. 



(5) 

 heaving — See heave. 



heavy floe — An ice floe more than 10 feet thick. 

 (59) Obsolete. 



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