AEROLOGY OF EXTRATROPICAL DISTURBANCES 
15 and 16 could probably be split into several surfaces, 
as in Fig. 9, by a more detailed analysis. 
Raethjen [50] has recently tried to explain the for- 
mation of the high-level cyclones associated with drops 
4 NOV. 1946 
0300 GCT 
Fre. 14.—500-mb chart over North America, 0300 GMT, 
November 4, 1946. Solid lines are contours of 500-mb surface, 
dashed lines are isotherms (degrees centigrade). 
of cold air as a result of isentropic exchange of air par- 
cels conserving their absolute angular momentum. This 
process would obviously result in a change in circula- 
s 
\ 
1 
\ 
"GLASGOW 
768 
(2086') 
GRAND 
JUNCTION 
476 
EL PASO 
270 
(3916') 
(4602') 
ALBUQUERQUE 
365 
(5314) 
LANDER 
576 
(5352') 
Fria. 15.—Vertical north-south cross section through center 
of high-level cyclone of Fig. 14. Heavy line indicates tropo- 
pause, solid thin lines isentropes (degrees absolute) and dashed 
lines isotherms (degrees centigrade). 
617 
tion (increasing cyclonic vorticity in the central upper 
parts of the cold drop) similar to the vertical circula- 
tion outlined here. Quite different points of view have 
been expressed by Rossby [54] in his paper on the 
meridional movement of sinking cold domes. It seems 
obvious that the problem of the extreme meandering of 
the west-wind belt resulting in the formation of cold 
upper lows must be subjected to further investigations 
before the nature of the process can be regarded as 
completely clarified. 
The meandering of the belt of upper westerlies and 
the deformation of the upper polar front also result iz 
an increase of the amplitude of the warm upper ridges. 
In extreme cases a warm ridge can be completely sepa- 
Y 
OKLAHOMA 
CITY 
353 
(1304') 
ALBUQUERQUE 
365 
(5314') 
Fie. 16.—Vertical west-east cross section through center of 
high-level cyclone of Fig. 14. Legend as in Fig. 15. 
rated from its warm source region in the south. The 
meandering then results in the formation of closed 
warm upper anticyclones and the belt of strong wester- 
lies can be re-established south of it. These types of 
warm upper anticyclones consist mostly of cold polar 
air masses in the lower layers and therefore appear, in a 
superficial analysis, as cold polar anticyclones. The 
true nature of these anticyclones has been elucidated 
through a number of synoptic investigations. The struc- 
ture of such a warm upper anticyclone has been sub- 
jected to a detailed analysis by Berggren, Bolin, and 
Rossby [4]. The case they studied has been used as a 
model for the upper anticyclone over northern Europe 
shown in Fig. 4. The pronounced anticyclonic vorticity 
in these warm upper highs can partly be explained as a 
result of advective transport of low absolute vorticity 
