BIBLIOGRAPHY 
(Eee 
231 
representative observations (II1)— 
those which give the true or typi- 
cal conditions of the air mass; hence 
they must be relatively uninfluenced 
by local conditions and taken from 
outside the transition zones and 
fronts. 
Rossby diagram (III)-—a_ thermo- 
dynamic diagram making use of 
the highly conservative air mass 
properties: partial potential tem- 
perature, equivalent-potential tem- 
perature and mixing ratio. 
secondary fronts (V1)—fronts which 
develop at some distance from the 
principal fronts of the cyclone. 
These fronts are often the result 
of dynamic effects behind the cold 
front, or are merely loop back oc- 
clusions. 
slope of a front (V)—the tangent of 
the angle formed by the discon- 
tinuity surface and a _ horizontal 
plane. 
source region (11)—an extensive area 
of the earth’s surface character- 
ized by sufficiently uniform surface 
conditions and which is so placed in 
respect to general circulation that 
masses of air may remain over them 
sufficiently long to take on fairly 
definite properties. 
specific humidity (I1)—the mass of 
water vapor in a unit mass of moist 
air. q—622 e/p grams per kilogram. 
squall head (V1)—the piled up cold 
air at the cold front, sometimes 
taking the form of an overhanging 
tongue. Also “line squall’. 
stability (1)—a vertical distribution 
of temperature such that particles 
will resist displacement from their 
level. In the case of dry air the 
lapse rate for stability will be less 
than the dry adiabat; in that of 
saturated air, less than the satura- 
tion adiabat. 
stratification (V)—a layering of the 
atmosphere, so that each layer is 
characterized by a particular tem- 
perature distribution and moisture 
content. Instability tends to wipe 
out stratification as it brings about 
mixing. 
subsidence (I1V)—an extensive sink- 
ing process most frequently ob- 
served in polar anticyclones. The 
subsiding air is dynamically 
warmed and made more stable. 
superadiabatic (1, VIII, [X)—a lapse- 
rate greater than the dry adiabatic; 
absolute instability. Mechanical in- 
stability may be implied also. 
surface of discontinuity (V)—the 
sloping boundary zone between air 
masses of different properties (see 
discontinuity). 
symbols—used throughout the series 
and in the formulas given herein: 
é@ —vapor pressure 
e =saturation vapor pressure 
WL 
f =relative humidity 
p =total pressure 
q =specific humidity 
t, t’=dry, and wet, bulb tempera- 
(HODHS, TAS Oo, il Id Ore in °C 
T=absolute temperature 
T’=wet-bulb temperature (°A) 
w =mixing ratio 
© =potential temperature 
fT equivalent temperature 
@ =equivalent-potential tem- 
perature 
® =partial potential temperature 
0’=wet-bulb 
ture. 
go entropy 
potential tempera- 
tephigram (VIII1)—a thermodynamic 
diagram for estimating the quan- 
tity of available convective energy 
in the overlying air column; also 
applied to the graph of an in- 
dividual sounding plotted with co- 
érdinates temperature and entropy. 
transition zone (V)—the zone at a 
discontinuity wherein the proper- 
ties are characteristic neither of one 
air mass nor the other, but lie some- 
where between the two. It is now 
customary to assume that all the 
air in the transition zone belongs 
to the colder air mass, the air in 
warm sectors being considered more 
nearly homogeneous. 
