566 
and are at the same time not overly restrictive. Perhaps 
the way out of this dilemma is offered by new electronic 
high-speed computing equipment. 
CONCLUSIONS 
In the brief summary of recent work on the general 
circulation presented above, three basic aspects have 
been stressed. The first deals with what is known of the 
observed fields of atmospheric mass and motion, both 
in their normal state and in their week-to-week or 
month-to-month variations. While there is a fair de- 
lineation of the pressure field in the Northern Hemi- 
sphere and in the lower troposphere for a short period 
of years, there are considerably less systematic analyses 
of wind and moisture on a hemispheric scale. The second 
aspect concerns certain quantities such as divergence, 
vertical motion, heat sources and sinks, transport of 
mass and momentum, and other factors which can be 
derived from the fundamental fields of wind and pres- 
sure. Finally, there has been some discussion of the 
physical interpretation of this great mass of observa- 
tions. It is this interpretation which provides a basis 
for long-range forecasting. 
Much work remains to be done in all three aspects of 
the problem, especially in the last. At present there is 
no completely quantitative utilization of theoretical 
findings in forecasting. Perhaps the closest approach 
to this is confined to certain relatively simple applica- 
tions of the classical hydrodynamical concept of con- 
servation of vorticity. This meager result is due largely 
to the fact that, just as in other sciences, advances in 
theoretical meteorology must go hand-in-hand with 
advances in observation. For example, there appears to 
be much promise in the application of electronic ma- 
chines and numerical integration methods to the prob- 
lem of short- and long-range forecasting. However, even 
this will be of little avail unless it is accompanied by a 
better understanding of atmospheric processes through 
more intensive studies of existing data and improvement 
in observational techniques. 
In various places throughout the text the authors 
have suggested several ways in which further progress 
in observational studies can be made. Perhaps the most 
important of these are the completion of the historical 
Northern Hemisphere map project for the war years 
1939 through 1945. With a complete and improved 
supply of historical data, further attempts can be made 
to obtain a more accurate picture than we now have of 
the normal state of the circulation at many levels, and 
to study such things as the characteristics of atmos- 
pheric waves and circulation indices. Clearly many 
other projects in addition to those mentioned can be 
suggested which will lead to better utilization of our 
existing supply of data. 
Tn addition to utilizing existing data more effectively, 
meteorologists have the responsibility of seemg that 
future supplies of hemispheric data are improved. This 
improvement appears to be more necessary in quality 
rather than in quantity. Thus, observational networks 
should be chosen so that there is a more even distribu- 
tion over the globe. Observations, including winds and 
THE GENERAL CIRCULATION 
moisture, should be taken from high atmospheric levels. 
The idea of the “polar year” or “aerological days” 
should be extended so that a global supply of data at 
all levels will be available for at least one year. 
REFERENCES 
1. Arr WeatHer Service, Northern Hemisphere Historical 
Weather Maps, Sea Level and 500 Millibar. October 
1945 to September 1946 (to be completed through De- 
cember 1948). Washington, D. C. 
2. Bereeren, R., Bourn, B., and Rosssy, C.-G., “‘An Aero- 
logical Study of Zonal Motion, Its Perturbations and 
Break-Down.”’ Tellus, Vol. 1, No. 2, pp. 14-37 (1949). 
3. Berry, F. A., Jr., Botuay, H., and Brmrs, N. R., ed., 
Handbook of Meteorology. New York, McGraw, 1945. 
(See pp. 451-453) 
4, BserKNEs, J., and Houtmpos, J., ‘‘On the Theory of Cy- 
clones.’’ J. Meteor., 1:1-22 (1944). 
5. BserKnes, V., and others, Physikalische Hydrodynamik. 
Berlin, J. Springer, 1933. (See pp. 668-702) 
6. Bortman, R. S8., ‘“‘Empirical Corrections to Constant 
Absolute Vorticity Trajectories.” Trans. Amer. geophys. 
Un., 29 :324-330 (1948). 
7. —— The Interrelationship of Wavelength, Amplitude, and 
Wind Speed in Upper-Air Flow Patterns. Unpubl. Rep., 
Extended Forecast Sect., U.S. Weather Bureau, Wash- 
ington, D. C., 1949. 
8. Brooks, C. E. P., ‘“‘The Variation of Pressure from Month 
to Month in the Region of the British Isles.”’ Quart. J. R. 
meteor. Soc., 52:263-276 (1926). 
9. —— and others, ‘“‘Upper Winds over the World.”’ Geophys. 
Mem., No. 85, 149 pp. (1950). 
10. CHarney, J. G., ‘‘On the Seale of Atmospheric Motions.” 
Geofys. Publ., Vol. 17, No. 2 (1948). 
11. —— “On a Physical Basis for Numerical Prediction of 
Large-Scale Motions in the Atmosphere.”’ J. Meteor., 
6:371-385 (1949). 
12. —— and Extassen, A., ‘‘A Numerical Method for Pre- 
dicting the Perturbations of the Middle Latitude West- 
erlies.”’ Tellus, Vol. 1, No. 2, pp. 38-54 (1949). 
13. Cuapp, P. F., Further Empirical Studies of Wave Motion in 
the Westerlies. Unpubl. Rep., Extended Forecast Sect., 
U.S. Weather Bureau, Washington, D. C., 1948. 
14. Cressman, G. P., ‘‘On the Forecasting of Long Waves in 
the Upper Westerlies.”’ J. Meteor., 5:44-57 (1948). 
15. —— ‘Some Effects of Wave-Length Variations of the 
Long Waves in the Upper Westerlies.”’ J. Meteor., 6:56- 
60 (1949). 
16. Deranzt, A., ‘‘Die Zirkulation der Atmosphire in den gemas- 
sigten Breiten der Erde.”’ Geogr. Ann., Stockh., 3:209-266 
(1921). 
17. DEUTSCHER WETTERDIENST, Current Daily Sea-Level ana 
500-Mb Analyses. Bad Kissingen, 1949 et seq. 
18. Dines, W. H., ‘‘The Characteristics of the Free Atmos- 
phere.’’ Geophys. Mem., 2:45-76 (1919). 
19. Dorsey, H. G., Jr., and Brimr, G. W., “‘An Investigation 
of a Trajectory Method for Forecasting Flow Patterns 
at the Ten-Thousand-Foot Level.’ Res. Paper FR-08 in 
A Collection of Reports on Extended Forecasting Research. 
U.S. Weather Bureau, Washington, D. C., 1944. 
20. Drypren, H. L., “‘A Review of the Statistical Theory of 
Turbulence.”’ Quart. appl. Math., 1:7—42 (1943). (See p. 9) 
21. Exuiort, R. D., and Smrru, T. B., ‘‘A Study of the Effects 
of Large Blocking Highs on the General Circulation of the 
Northern-Hemisphere Westerlies.”” J. Meteor., 6:67-85 
(1949). 
