160 
AIR MASS ANALYSIS 
tongue has a maximum of precipita- 
tion in summer. It has been sug- 
gested by Wexler [23] that this pre- 
ferred site for the anticyclonic eddy 
is largely due to topography and re- 
sults from the field of solenoids to the 
north as well as from the field of sole- 
noids established between the warm 
Rocky Mountain region and the colder 
Pacific region. 
The point of injection of the moist 
tongue of the eastern eddy is nor- 
mally over Florida, in which region 
there is a summer maximum of rain- 
fall and a high frequency of thunder- 
storms. 
While there is a similarity of mean 
monthly isentropic charts for different 
summer months and from year to 
year, it should not be inferred that 
the moisture patterns are always the 
same. Considerable deviations from 
the mean state are always associated 
with considerable anomalies in rain- 
fall and temperature (Wexler and 
Namias [24]). Thus during the 
month of August, 1936, when one of 
the most severe droughts and heat 
waves occurred in the mid-west, the 
mean monthly pattern showed only 
one very extensive anticyclonic eddy 
covering the entire country rather 
than the normal double cellular pat- 
tern. 
In winter, when the mid-latitude 
solenoid field is situated farther to 
the south, the mean isentropic charts 
do not generally display any outstand- 
ing eddies. Simultaneously, the daily 
charts show pronounced eddies with 
moist and dry tongues. The in- 
dividual eddies then move rapidly. 
without preferring any particular 
site. While the above refers to the 
conditions over the North American 
continent, there can be little doubt 
that the principles outlined here ap- 
ply in a general way throughout the 
world. 
§ 10. REFERENCES 
[1] Rossby, C.-G., Thermodynamics Applied 
to Air Mass Analysis. Massachusetts 
Institute of Technology Meteorological 
Papers, Vol. I, No. 38, 1932. 
12] Rossby, C.-G., and Collaborators, Aero- 
logical Evidence of Large-Scale Mixing 
in the Atmospheie. Transactions of the 
American Geophysical Union, 18th An- 
nual Meeting, Pt. I, pp. 130-136, 1937. 
18] Rossby, C.-G., and Collaborators, Isen- 
tropic Analysis. Bulletin of the Ameri- 
can Meteorological Society, June-July, 
Vol. 18, pp. 201-209, 1937. 
[4] Shaw, Sir Napier: Manual of Meteor- 
ology. Vol. 3, The Physical Processes of 
Weather. Cambridge University Press, 
1933, pp. 259-266. 
L5 ] Rossby, C.-G., Dynamics of Steady Ocean 
Currents in the Light of Experimental 
Fluid Mechanics. Papers in Physical 
Oceanography and Meteorology, Massa- 
chusetts Institute of Technology and 
Woods Hole Oceanographic Institution, 
Vol. V, No. 1, 1936. 
16] Parr, A. E., On the Probable Relation- 
ship Between the Vertical Stability and 
Lateral Mixing Processes. Journal du 
Conseil, Vol. XI, No. 3, 1936. 
17] Ekman, V. W., Studien zur Dynamik der 
Meeresstr6mungen, Gerlands Beitr. Geo- 
physik, Vol. 36, p. 385, 1932. 
£18] Rossby, C.-G., Note on Shearing Stresses 
Caused by Large-Scale Lateral Mixing, 
Proceedings of the Fifth International 
Congress of Applied Mechanics, 1938. N. 
Y., 1939, pp. 379-381. 
[9] Grimminger,, G., The Intensity of Lat- 
eral Mixing in the Atmosphere as Deter- 
mined from Isentropie Charts. Tvransac- 
tions of the American Geophysical Union, 
Nineteenth Annual Meeting, 1938, Pt. I, 
p. 163. 
[10] Byers, H. R., On the Thermodynamic 
Interpretation of Isentropic (Charts. 
Monthly Weather Review, Vol. 66, No. 3, 
1938. 
[11] Tollmien, W., 
Ausbreitungsvorgange, 
Angewandte Mathematik 
WoL O, is GGG, IORo- 
[12] Rossby, C.-G., On the Mutual Adiust- 
ment of Pressure and Velocity Distribu- 
tions in Certain Simple Current Systems, 
I and Il. Sears Feundation: Jcurnal of 
Marine Research, Vol. I, Nos. 1 and 38, 
1937 and 1988. 
[13] Pekeris, C. l., Wave-Distribution in a 
Homogeneous Current. Transactions of 
the American Geophysical Union, Nine- 
teenth Annual Meeting, 1938, Pt. I, pp. 
163-164. 
[14] Namias, J., Forecasting Significance of 
Anticyelonie Eddies on Isentropic Sur- 
faces. Transactions of the American 
Geophysical Union, Nineteenth Annual 
Meeting, 1938, Pt. I, pp. 174-176. 
[15] Namias, J., The Use of Isentropic neal 
sis in Short Term Forecasting. Journal 
of the Aeronautical Sciences, Vol. 6, No. 
7, 1939. 
Berechnung turbulenter 
Zeitschrift fur 
and Mechanik, 
