OBSERVATIONAL STUDIES OF GENERAL CIRCULATION PATTERNS 
By JEROME NAMIAS and PHILIP F. CLAPP 
U. S. Weather Bureau, Washington, D. C. 
Any reasonably brief treatment of a subject so vast 
as “Observational Studies of General Circulation Pat- 
terns” is bound to be biased in its selection of material. 
To be sure, any and all real information derived from 
the atmosphere constitutes an integral part of the ma- 
terial upon which students of the general circulation 
must draw. Inasmuch as our knowledge of the general 
circulation is very far from complete, it is difficult at 
this time to decide what statistically or observationally 
determined facts are especially pertinent. In selecting 
these data the authors confess to a bias in the direction 
of hemispheric or world-wide phenomena and also to 
those facts which have emerged from a fifteen-year-old 
experiment in the anatomy and physiology of the gen- 
eral circulation with which the authors have had the 
pleasure to be affiliated [83]. 
NORMAL STATE OF THE GENERAL 
CIRCULATION OVER THE EARTH 
Sources of Data—Historical and Current. Ideally, 
the data upon which studies of general circulation pat- 
Fia. 1.—Typical data coverage at sea level for the Northern 
Hemisphere. Solid circles represent data actually received at 
1200Z June 25, 1949. Some data have been omitted over the 
Wnited States and parts of Europe because of space limita- 
jons. 
terns are based should consist of a series of complete 
and well-analyzed sea-level and upper-level charts cov- 
ering the globe or at least a hemisphere for a period of 
decades. At the present writing this ideal state of affairs 
is far from being realized. For the Northern Hemisphere 
the longest series of analyzed charts at sea level em- 
brace a period of about fifty years and at upper levels 
about fifteen years. Such a short period is woefully 
inadequate for studies of large-scale weather phenom- 
ena, particularly when one considers time intervals of 
a month or more. Furthermore, many of these charts 
are incomplete or maccurate, and the upper-air charts 
are mainly for one level only (either 700 or 500 mb). 
In the Southern Hemisphere the situation is materially 
worse, although it will be partly remedied in a few years 
after several units, including the Department of Me- 
teorology at the Massachusetts Institute of Technology, 
have completed files of Southern Hemisphere sea-level 
charts. The M.I.T. series began with January 1949. 
Figures 1 and 2 give some idea of the amount and 
extent of data currently available for the construction 
AN Sy Vie 
2 > = 
— - 
Ue 
Fig. 2—Typical data coverage at 500 mb. Small solid 
circles represent radiosonde data; large open circles, wind 
data; and large solid circles, both radiosonde and wind data 
actually received at 0300Z June 24, 1949. Winds are by pilot 
balloon, radar, or direction finder. The three observations near 
the pole and the five in the southwest Pacific centered at 20°N, 
147°E are aircraft reconnaissance data. 
of Northern Hemisphere charts at the Central Office of 
the U. S. Weather Bureau. This represents a vast im- 
provement over conditions existing ten years ago, 
largely as a result of the increasing need for data during 
World War II. 
551 
