Practical Exercises in Elementary Meteorology Part 1

Practical Exercises in Elementary Meteorology.

by Robert DeCourcy Ward.

PREFACE.

The advance of meteorology as a school study has been much hampered by the lack of a published outline of work in this subject which may be undertaken during the school years. There are several excellent text-books for more advanced study, but there is no laboratory manual for use in the elementary portions of the science. In many secondary schools some instruction in meteorology is given, and the keeping of meteorological records by the scholars is every year becoming more general. There is yet, however, but little system in this work, and, in consequence, there is little definite result. The object of this book is to supply a guide in the elementary observational and inductive studies in meteorology. This Manual is not intended to replace the text-books, but is designed to prepare the way for their more intelligent use. Simple preliminary exercises in the taking of meteorological observations, and in the study of the daily weather maps, as herein suggested, will lay a good foundation on which later studies, in connection with the text-books, may be built up. Explanations of the various facts discovered through these exercises are not considered to lie within the scope of this book. They may be found in any of the newer text-books.

This Manual lays little claim to originality. Its essential features are based on the recommendations in the Report on Geography of the Committee of Ten. A scheme of laboratory exercises, substantially the same as that proposed in this Report, was, for some fifteen years, the basis of the work in elementary meteorology done in Harvard College under the direction of Professor William M. Davis. The plan proposed by the Committee of Ten has been thoroughly tested by the writer during the past five years, not only in college cla.s.ses, but also in University Extension work among school teachers, and the present book embodies such modifications of that scheme and additions to it as have been suggested by experience. Emphasis is laid throughout this Manual on the larger lessons to be learned from the individual exercises, and on the relations of various atmospheric phenomena to human life and activities. No attempt is made to specify in exactly what school years this work should be undertaken. At present, and until meteorology attains a recognized position as a school study, teachers must obviously be left to decide this matter according to the opportunities offered in each school. The general outline of the work, however, as herein set forth, is intended to cover the grammar and the high school years, and may readily be adapted by the teacher to fit the circ.u.mstances of any particular case.

This book contains specific instructions to the student as to the use of the instruments; the carrying out of meteorological observations; the investigation of special simple problems by means of the instruments; and the practical use of the daily weather maps. The Notes for the Teacher, at the end of the book, are explanatory, and contain suggestions which may be useful in directing the laboratory work of the cla.s.s.

It has been the privilege of the author during the past ten years to study the science of meteorology, and the methods of teaching that science, under the constant direction of Professor William Morris Davis, of Harvard University. To Professor Davis the author is further indebted for many valuable suggestions in connection with the arrangement and treatment of the subject-matter of this book. Thanks are due also to Mr. William H.

Snyder, of Worcester (Ma.s.s.) Academy, and to Mr. John W. Smith, Local Forecast Official of the United States Weather Bureau, Boston, Ma.s.s., for valued criticisms.

ROBERT DEC. WARD.

HARVARD UNIVERSITY, CAMBRIDGE, Ma.s.s., September, 1899.

INTRODUCTION.

THE IMPORTANCE OF METEOROLOGY: ITS RELATIONS TO MAN.

We live in the laboratory of the earth's atmosphere. The changes from hot to cold, wet to dry, clear to cloudy, or the reverse, profoundly affect us. We make and unmake our daily plans; we study or we enjoy vacations; we vary our amus.e.m.e.nts and our clothing according to these changes. The weather forecasts for the day in the newspaper are read even before the telegraphic despatches of important events. Sailors about to put to sea govern themselves according to the storm warnings of our Weather Bureau.

Farmers and s.h.i.+ppers of fruit, meat, and vegetables anxiously watch the bulletins of cold or warm waves, and guard against damage by frost or excessive heat. Steam and electric railways prepare their snow-plows when a severe snowstorm is predicted.

Meteorology, the science of the atmosphere, is thus of very great interest and importance. There is no subject a knowledge of which does more to make our daily life interesting. Since we live in the midst of the atmosphere and cannot escape from the changes that take place in it, we must, consciously or unconsciously, become observers of these changes. Examples of the varying processes at work in the atmosphere are always with us.

There is no end to the number and the variety of our ill.u.s.trations of these processes. Man is so profoundly affected by weather changes from day to day that all civilized countries have established weather services.

Observers taking regular weather records are stationed at thousands of different places in all parts of the world, and the observations which they make are used by meteorologists in preparing daily weather maps and forecasts, and in studying the conditions of temperature, winds, and rainfall. In the United States alone there are about 3000 of these observers.

These observations are not made on land only. Hundreds of s.h.i.+p captains on all the oceans of the world are making their regular daily meteorological records, which at the end of the voyage are sent to some central office,[1] where they are studied and employed in the preparation of Pilot Charts for the use of mariners. By means of these ocean meteorological observations, which were first systematized and carried out on a large scale under the direction of Lieutenant Matthew Fontaine Maury (born, 1806; died, 1873), of the United States Navy, it has become possible to lay out the most favorable sailing routes for vessels engaged in commerce in all parts of the world.

[Footnote 1: In the United States, marine meteorological observations are forwarded to the United States Hydrographic Office, Navy Department, Was.h.i.+ngton.]

So important is a knowledge of the conditions of the winds and the weather, that scientific expeditions into unexplored or little-known regions give much of their time to meteorological observations. On the famous Lady Franklin Bay Expedition (1881-1884) of Lieutenant (now General) A. W. Greely, of the United States Army, meteorological observations were kept up by the few feeble survivors, after death by disease and starvation had almost wiped out the party altogether, and when those who were left had but a few hours to live unless rescue came at once. On Nansen's expedition to the "Farthest North," on Peary's trips to Greenland, and on every recent voyage to the Arctic or the Antarctic, meteorological instruments have formed an important part of the equipment.

Not content with obtaining records from the air near the earth's surface, meteorologists have sent up their instruments by means of small, un-manned balloons to heights of 10 miles; and the use of kites for carrying up such instruments has been so successful that, at Blue Hill Observatory, near Boston, Ma.s.s., records have been obtained from a height of over 2 miles.

Observatories have also been established on mountain summits, where meteorological observations have been made with more or less regularity.

Such observatories are those on Pike's Peak, Colorado (14,134 feet), Mont Blanc, Switzerland (15,780 feet), and on El Misti, in southern Peru. The latter, 19,200 feet above sea level, is the highest meteorological station in the world.

The study of the meteorological conditions prevailing over the earth has thus become of world-wide importance. In the following exercises we shall carry out, in a small way, investigations similar to those which have occupied and are now occupying the attention of meteorologists all over the world.

PRACTICAL EXERCISES IN ELEMENTARY METEOROLOGY.

PART I.--NON-INSTRUMENTAL OBSERVATIONS.

CHAPTER I.

OBSERVATIONS OF TEMPERATURE; WIND DIRECTION AND VELOCITY; STATE OF SKY, AND RAINFALL.

Before beginning observations with the ordinary instruments, accustom yourself to making and recording observations of a general character, such as may be carried out without the use of any instruments whatever. Such records include: _Temperature_; _Wind Direction and Velocity_; _State of the Sky_, _and Rainfall_.

=Temperature.=--In keeping a record[2] of temperature without the use of a thermometer, excellent practice is given in observations of the temperature actually felt by the human body. Our bodies are not thermometers. They do not indicate, by our sensations of heat or cold, just what is the temperature of the surrounding air, but they try to adjust themselves to the conditions in which they are. This adjustment depends on many things beside the temperature of the air; _e.g._, the moisture or humidity of the air; the movement of the air; the temperature and the nearness of surrounding objects. In summer, a day on which the temperature reaches 80 or 85 often seems much hotter than another day on which the temperature rises to 95. In winter, temperatures registered by the thermometer as 10 or 15 above zero often feel a great deal colder than temperatures of -5 or -10. In recording your observations on temperature, the record book may be divided into columns as follows:--

[Footnote 2: Each scholar will need a blank book in which to preserve the observations.]

SAMPLE RECORD OF TEMPERATURE.

+---------+---------+--------------+------------------------------------+ DATE. HOUR. TEMPERATURE. REMARKS. +---------+---------+--------------+----------------------------------- + Jan. 16 9 A.M. Chilly " " 12 M. Warmer " " 4 P.M. " Growing slowly warmer all day. " 17 8 A.M. Warm About the same as Jan. 16, 4 P.M. " " 11 A.M. Cooler Began to grow cooler about 10 A.M. " " 3 P.M. Colder Steadily becoming colder. +---------+---------+--------------+------------------------------------+

The following are some of the questions you should ask yourself in carrying out this work. It is not expected that you will be able to answer all these questions at once, but that you will keep them in mind during your studies, and try to discover the answers, as a result of your own observations.

How does it feel to you out of doors to-day? Is it hot, warm, cool, or cold? What is the difference between your feelings yesterday and to-day?

Between day before yesterday and to-day? Have you noticed any _regular_ change in your feelings as to warmth and cold during three or four successive days? During the past week or two? During the past month? Is there any difference between the temperature of morning, noon, afternoon, and evening? Is there any _regular_ variation in temperature during the day? Have there been any _sudden_ changes in temperature during the last few days? Have these sudden changes brought warmer or cooler weather? Has the warmer or cooler weather continued for a day or so, or has another change quickly followed the first? Have the sudden changes, if you have noted any, come at any regular times (as morning, afternoon, evening) or at irregular intervals? Does there seem to you to be any definite system, of any kind, in our changes of temperature? In what ways are people in general affected by hot weather? By cold weather? What difference does a very hot or a very cold day make in your own case?

=Wind Direction and Velocity.=--Wind is an important meteorological element because it has many close relations to human life. It affects very markedly our bodily sensations of heat or cold. A cold, calm day is pleasanter than a cold, windy day. On the other hand, a hot, calm day is usually much more uncomfortable than a hot, windy day. High winds cause wrecks along seacoasts and damage houses, crops, and fruit trees. Sea breezes bring in fresh, cool, pure air from the ocean on hot summer days.

In the tropics the sea breeze is so important in preserving the health of Europeans in many places that it is known as "the doctor." The movement of wind through large cities carries off the foul air which has collected in the narrow streets and alleys, and is thus a great purifying agent.

Record the _direction of the wind_ according to the four cardinal points of the compa.s.s (N., E., S., and W.) and the four intermediate points (NE., SE., SW., and NW.). The direction of the wind is the point _from_ which the wind blows. You can determine the points of the compa.s.s roughly by noting where the sun rises and where it sets.

Note the _velocity of the wind_ according to the following scale, proposed by Professor H. A. Hazen of the United States Weather Bureau.

0 CALM.

1 LIGHT; just moving the leaves of trees.

2 MODERATE; moving branches.

3 BRISK; swaying branches; blowing up dust.

4 HIGH; blowing up twigs from the ground, swaying whole trees.

5 GALE; breaking small branches, loosening bricks on chimneys.

6 HURRICANE or TORNADO; destroying everything in its path.

The record book will need two additional columns when wind observations are begun, as follows:--

SAMPLE RECORD OF TEMPERATURE AND WIND.