McGRAW-HILL 

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HORACE ROBERT BYERS, Sc.D. 

Professor of Meteorology 

Texas A & M University 

General 

Meteorology 

FOURTH EDITION 
This book was set in Times New Roman. 


The editors were Robert H. Summersgill, Brete C. Harrison, and Susan Gamer; 


the cover was designed by Joseph Gillians; 


and the production supervisor was Thomas J. LoPinto. 


New drawings were done by John Cordes, J & R Technical Services, Inc. 


The Maple Press Company was printer and binder. 


Library of Congress Cataloging in Publication Data 


Byers. Horace Robert, date 

General meteorology. 

First ed. published in 1937 under title: Synoptic 

and aeronautical meteorology. 

I. Meteorology. I. Title. 

QC861.2.B9 1974 551.5 73-19886 

ISBN 0-07-009500-0 

GENERAL 

METEOROLOGY 

Copyright © 1959, 1974 by McGraw-Hili, Inc. All rights reserved. 


Copyright 1944 by McGraw-Hili, Inc. All rights reserved. 


Formerly published under the title of SYNOPTIC AND AERONAUTICAL 


METEOROLOGY copyright 1937 by McGraw-Hili, Inc. All rights reserved. 


Printed in the United States of America. No part of this publication may be repr<4 


stored in a retrieval system, or transmitted, in any form or by any means, 


electronic, mechanical, photocopying, recording, or otherwise, 


without the prior written permission of the publisher. 


4567890 MAMM 7987 
218 GENERAL METEOROLOGY 

CfJ is V", = Or = OR cos CfJ, where r is the radius of a latitude circle and R is the radius 

of the earth. The relative west-to-east speed, which would be the 11 component of 

the wind, is /I = VA - V"" where VA is the absolute west-to-east component. Conservation of the absolute angular momentum means that VA R cos CfJ = const, or 

VA, R cos CfJ2 = VA,R cos CfJI 

(9-1) 

Consider particles displaced from the equator to 30°. Take 110 as - 5 m sec -1 (east 

wind at equator). Then 

V Ao = V",o - 5 

cos 0 

VA,o = (V",o - 5) -30 = 1.155(V",o - 5) cos 

1130 = VA,o - V""o 1.155(V",o - 5) - OR cos 30 

= 1.155( 464.45 - 5) - (464.45 x 0.866) 

= 530.7 402.2 

= 128.5 m sec- 1 

West winds with speeds of this magnitude are more than twice the speeds observed 

in extreme cases in the strongest high-level jet streams. If the above example were 

carried to latitude 60°, the wind would be at 686.7 m sec - 1. The speeds that would 

! : 	 result from conservation of angular momentum are so far from the real speeds that 

one immediately realizes that something must happen to the wind system. The 

reduction of the winds to speeds that we normally observe cannot be accounted for 

by friction, which at least in the upper air, probably could reduce them by only a 

few percent. 

What happens is that the meridional circulation breaks down into smaller 

circulations. Bergeron1 depicted a system containing a meridional circulation of 

three cells. This system, considerably modified, is shown in Fig. 9-1. The net 

, , meridional circulation is represented in vertical cross section around the profile of the 

I earth, and the actual wind directions at the surface of the earth are shown within 

the circumference. Throughout the atmosphere the meridional components are on 

the average less than one-tenth of the zQnal componentsJExcept for a belt of deep 

easterlies around the equator, the upper winds are prevailingly from the west. At 

the surface, three wind belts are noted in each hemisphere: the trade winds of low 

latitudes, the middle-latitude westerli;s, and the polar easterlies. 

1 T. Bergeron, ()ber die Dreidimensional Verknilpfende Wetterilnalyse, Geofysiske 

Publikasjoner, vol. 5, no. 6, 1928. 

~~~ -Rjv,£ 1. I 
----- --- ----

__ 

THE GENERAL CIRCULATION 219 

R is the radius 

component of 

Iponent. Con­

= const, or 

S «PI 

rpl (9-1) 

«P2 

5 m sec - 1 (east 

)s 30 

speeds observed 

ve example were 

?eeds that would 

. real speeds that 

l1d system. The 

be accounted for 

: them by only a 

lwn into smaller 

ial circulation of 

g. 9-1. The net 

l the profile of the 

are shown within 

Imponents are on 

for a belt of deep 

)m the west. At 

ade winds of low 

.teranalyse, Geofysiske 

--- .. - .

~~~ _._~pQJ.Ji tL__ F_~l!J:~l-Q~~J___.~_

.­- _---'!J> WesterlIes __~ • 

ZJ .::':-~=-==-@~~~IDJjQlC==-~.__. r; ~~~___ olE ~~-=­ ~_._-.--- Trade Winds <E .­

..•________ ~=~.-~----rrl.-C1~==-~

~~~ 

~_QJJ~IQR!~j... __ ~.Q!:'!..~~lt. ~_~ ___ :. 

__ Trade Win~ 

--====-~-­ =--==--:'=:=~QB":;J'=:I~fi tJ.LJ: 

~­Westerlies __ ---

------,..

~ 

~~~~~~;~~ 

FIGURE 9-1 


Schematic representation of the general circulation, modified after Bergeron. 


The pressure-wind relationship applied to the surface circulation requires a 

belt of high pressure at about 300 N and S of the equator. This belt is called the 

"horse latitudes."l Low pressure is required between the westerlies and the polar 

easterlies. 

Except for the easterlies of the trade-wind belt, the surface wind systems are 

quite variable. The continents develop thermally induced wind and pressure systems, 

with relatively high pressures over the land areas in winter and lower pressures in 

summer. The wind systems pictured in Fig. 9-1 are best marked over the oceans, 

particularly in the Southern Hemisphere where the continental areas are small. 

The low-pressure area around the latitude of 600 is most inconstant. It is an average 

made up of the effects of all the moving cyclones of middle and high latitudes. The 

polar highs are also quite variable, especially in the Northern Hemisphere. 

It is apparent from Fig. 9-1 that low-level convergence occurs in the meridional 

components at the equator between the trade winds of the two hemispheres and also 

1 It is thought that the name is derived from the numerous bodies of horses seen 

floating on the sea in these latitudes in the seventeenth century. It is related that 

sailing vessels transporting horses to the New World were becalmed in the highpressure center and. running low on feed and water, reduced their cargoes in midocean. 
Figure 4.19 

Path and dally positions of a (or;utanl-ievel balloon in tlie Southern 

!!..cllli.lI/!trTf lIj)per lVCJferliesfAifer /aullchmg al ChristcllUrcll, 1~rn;; Zcaland, 

all March 30, 1966, the GHOST balloon drifted at an altitude of about 12 km 

ill IIpj)cr.ielll'l walles for 3) days. (NCA,R [National Center for Atmospheric 

Re,earch], Boulder, Colorado) 

in large-scale Illation systems to retain a constant spin, or angular momenWill. abollt the eartb's axis of rotation. A stream of air moving toward the 

eqll~ltor adopts a cyclonic cunatllre (collnterclockwise in the Northern 

Hcmisphere) relatiyc to the surface at the lower latitude as the distance 

from thc axis of rotation incrcases. Eventllally the curvcd path turns the 

wind back towanl the polc. Passin?; its origin;ll latitude, the wind takes 

;\ll oppositc (tllat is, anticyclonic) curvature relative to the earth as it 

comes closer to the polar axis, where the rotational yelocity is less. (These 

effects arc easily dClllollStratcd 011 a /!,Iobc.) The result iug Rossby 11'1H'(,S 

llI;IY lJayc lengths of 3,000 to (),OOO kl1l, permitting thrcc to 5i;.; (j)'(ul11­

polar \\,;lyes that correspond to surface paths of depressions and anticyclones in the wCSlcrIie~ (see }iiRure ·Ll9). Thcir length, amplitude, amI 

position are influcnccd by dilfercntial heating at the surface ;tnd by ex91