Chapter 12 — THE GOVERNING FUNDAMENTALS OF METEOROLOGY 



Since gravity varies with latitude and height 

 above sea level, so must weight vary with the 

 same factors,, Thus, you will weigh more at 

 the poles than at the Equator and more at sea 

 level than atop a mountain. In a comparison of 

 mass and weight, mass will remain constant 

 no matter where it is, but weight will vary 

 with latitude and height above sea level. 



Volume 



Volume is the measure of the amount of 

 space which matter occupies. The volume of 

 rectangular objects is found directly by 

 obtaining the product of their length, width, 

 and depth. For determining the volume of 

 liquids and gases, special graduated containers 

 are used. 



Density 



The mass of a unit volume of a substance 

 or mass per unit volume is called density. 

 Usually we speak of substances being heavier 

 or lighter than another when comparing equal 

 volumes of the two substances. 



Since density is a derived quantity, the 

 density of an object can be computed by dividing 

 its mass (or weight) by its volume. The formula 

 for determining the density of a substance is 



D = ^L 

 V 



where D stands for density, M for mass, and 

 V for volume. 



From this formula, it is obvious that with 

 mass remaining unchanged, an increase in 

 volume causes a decrease in density, and a 

 decrease in volume causes an increase in 

 density. 



The density of gases is derived from the 

 same basic formula as the density of a solid. 

 Pressure and temperature also affect the density 

 of gases. This effect is discussed later in this 

 chapter under gas laws. Another notable effect 

 is the moisture content of a gas. 



SYSTEM OF MEASUREMENTS 



To properly relate to the field of meteor- 

 ology, the Aerographer should have a basic 

 understanding of the science of measurement 

 (metrology). When you can measure what you 



are talking about and present it in numerical 

 values, you then have a knowledge of your 

 subject. From early times requirements for 

 having a measurement system were needed. 

 There are many such systems throughout the 

 world today; but, on an international scale, 

 three fundamental quantities, length (meter/ 

 metre), mass (kilogram), and time (second), 

 have been recognized for use in science and 

 research. It is for this reason that the Metric 

 System (CGS, centimeter-gram- second) will be 

 discussed in the following paragraphs, with 

 brief points of discussion on the English System 

 (FPS, foot-pound- second). 



CGS AND FPS SYSTEMS 



The metric system is a decimal system 

 similar to that used in the money system of 

 the United States, in that each unit is one- 

 tenth the size of the next larger unit of measure. 

 It is the system most widely used, and it is 

 not improbable that before many years this 

 system will receive worldwide adoption. 



The metric system is not difficult to learn. 

 The meter is the unit of length, and the gram 

 is the unit of mass. The common subdivisions 

 of each of these units is then broken down by 

 the use of certain prefixes such as centi — 

 meaning one one-hundredth— and milli — meaning 

 one one-thousandth. The most common multiple 

 for these units is formed by using the prefix 

 kilo which means one thousand. (See table 12-1.) 



A meter is equivalent to approximately 39.37 

 inches. The prefixes are used to indicate larger 

 or smaller units of the meter. 



Other quantities derived from length are the 

 area and the volume. The standard unit of 

 measure for area is the square centimeter, or 

 cm^. For volume, the unit most used is a cube 

 with an edge of unit length. In the English 

 system, volume is usually measured in cubic 

 feet or cubic inches. Thus, the unit is a cube 

 1 foot or 1 inch on each edge. In the metric 

 system the cubic centimeter or cubic meter 

 is used. Another unit commonly used in the 

 metric system is the LITER. The liter is the 

 volume of a cube 10 centimeters on each edge. 

 The liter, therefore, contains 1,000 cubic 

 centimeters. 



Since mass in the CGS system is measured 

 in grams, and the unit volume in the CGS 

 system is 1 cubic centimeter, density may be 



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