1036 
the pressure at the surface is 1000 mb. From the graph 
the depth of precipitable water between any two pres- 
sure levels aloft can also be obtained when the potential 
dew point is known. Precipitable-water tables [82] for 
combinations of variables involving either pressure or 
HYDROMETEOROLOGY 
are appreciably reduced in most practical applications. 
To achieve greater realism, however, refined assump- 
tions can be formulated from synoptic studies of temper- 
ature and moisture stratifications, storm type by storm 
type. For instance, it is apparent that a saturated, 
TEMPERATURE 
°“F 140 320392464 526572 608 624 680 7TI6 75.2 
*% -10-402468 10 12 14 i6 18 20 22 24 
200 : = 
HE | 
300 
|) ila i ail 
ALTA [ 
= Ll 
ea} 1] rare 
= = 
uw 400 
[neg L} 
E + Tes A 
w nt 
wo a ——] t = 
a nl al my pL ee 
500 LH 4 op VAI 
N I 
H 
600 4 Be f_\_|f al 
AAAS ++ [ V4-427_ | | 7g 
ial \, 
a) et 4 Al Al ine InGal ma 
700 PEEEEEELEEH 
Co) 0.5 1.0 15 2.0 2.5 3.0 3.5 4.0 4.5 5.0 
PREGIPITABLE WATER (IN.) 
TEMPERATURE 
°F 140 284 356 428 50.0 536 572 608 64.4 68.0 716 75.2 78.8 82.4 °F 
-10-6 -202 46 8 10 12 14 16 18 20 22 24 26 28 °C 
700 | [ p 305 
[| a IL 10 
a a a = Je | A -l| atl 
Ey i = - 2.494 - 
B i , iz sj 
= 800 , rapa 
a 183. 6 
uJ L_! 
uw _ r + 
=) =| 5 aT eR? Ey 
reehwel’ 4 cet! 
wo Fy (Kil of Ff 
Ww 900 uF - noe [tt [a — 
ce /; ut! Ved . 
& ZL Sa A F Ho NOTE: 
5-02.61 2) of DOTTED GURVE SHOWS-— 
Asal [ | PRESSURE AT WHIGH 
| [| 0°G IS ATTAINED BY 
2 LIFTING 
1000 
(0) 0.5 1.0 1.5 2.0 2.5 
PRECIPITABLE WATER (IN.) 
Fic. 2—Depths of precipitable water in a column of air of giv 
with a pseudoadiabatic lapse rate fo 
height have recently been prepared for hydrometeor- 
ological use. 
The few tests of this assumption which have been 
possible in heavy rainstorms indicate that significant 
deviations may sometimes occur. Since, as will be 
discussed later, the most common use of precipitable- 
water values in hydrometeorology involves ratios of W 
at various dew points, errors inherent in the assumption 
en height above 1000 mb, under the assumption of saturation 
r the indicated surface temperatures. 
pseudoadiabatic atmosphere is not particularly close to 
reality in the case of convective instability, a cireum- 
stance which frequently characterizes sizable rain- 
storms. Whether the maximum possible storm possesses 
a pseudoadiabatic lapse rate in saturated air has not 
been established, but this is usually accepted as a 
reasonable assumption. Investigation is needed to deter- 
mine whether it is possible to maximize theoretical 
