CHAPTER 2
ATMOSPHERIC PHYSICS
The science of physics is devoted to finding,
defining, and reaching solutions to problems. It is the
basic science that deals with motion, force, and energy.
Physics, therefore, not only breeds curiosity of one’s
environment, but it provides a means of acquiring
answers to questions that continue to arise.
Atmospheric physics is a branch of physical
meteorology that deals with a combination of dynamic
and thermodynamic processes that account for the
existence of numerous atmospheric conditions.
To understand the weather elements and to analyze
meteorological situations you must know how to apply
the fundamental principles of physics. This does not
mean that you must be able to understand all of the
complicated theories of meteorology. It does mean,
however, that you should have a working knowledge of
elementary physics. You should learn how to apply the
rules of physics to understand how the atmosphere
works. This is necessary to perform your duties as an
Aerographer’s Mate in a creditable manner.
MOTION
LEARNING OBJECTIVE: Describe the
laws of motion and determine how motion is
affected by external forces.
Any general discussion of the principles of physics
must contain some consideration of the way in which
mass, force, and motion are related. In physics, the laws
of motion state that an object at rest never starts to move
by itself; a push or a pull must be exerted on it by some
other object. This also applies to weather. Weather has
complex motions in the vertical and horizontal planes.
To fully understand how and why weather moves, you
must have a basic knowledge of motion and those
external forces that affect motion.
TERMS
In dealing with motion several terms should be
defined before you venture into the study of motion.
These terms are inertia, speed, direction, velocity, and
acceleration.
Inertia
An object at rest never moves unless something or
someone moves it. This is a property of all forms of
matter (solid, liquid, or gas). Inertia, therefore, is the
property of matter to resist any change in its state of rest
or motion.
Speed
Speed is the rate at which something moves in a
given amount of time. In meteorology, speed is the term
that is used when only the rate of movement is meant. If
the rate of movement of a hurricane is 15 knots, we say
its speed is 15 knots per hour.
Direction
Direction is the line along which something moves
or lies. In meteorology, we speak of direction as toward
or the direction from which an object is moving. For
example, northerly winds are winds COMING FROM
the north.
Velocity
Velocity describes both the rate at which a body
moves and the direction in which it is traveling. If the
hurricane, with its speed of 15 knots per hour, is
described
as
moving
westward,
it
now
has
velocity—both a rate and direction of movement.
Acceleration
This term applies to a rate of change of the speed
and/or the velocity of matter with time. If a hurricane,
which is presently moving at 15 knots, is moving at 18
knots 1 hour from now and 21 knots 2 hours from now,
it is said to be accelerating at a rate of 3 knots per hour.
LAWS OF MOTION
Everything around us is in motion. Even a body
supposedly at rest on the surface of Earth is in motion
because the body is actually moving with the rotation of
Earth; Earth, in turn, is turning in its orbit around the
Sun. Therefore, the terms rest and motion are relative
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