CE322 Basic Hydrology
Jorge A. Ramirez
Computation of Precipitable Water - Example
Compute the precipitable water for a saturated column of atmosphere extending 10 km up from the ground surface. Assume the surface pressure is 101300 Pa, the surface temperature is 30 C and the ambient lapse rate is 6.5 K/km.
Precipitable water:
The solution is presented in tabular form. The columns of the table are computed as indicated below.
Column 1: Elevation in km
.
Column 2: Linear vertical temperature distribution.
Column 3: Vertical pressure distribution assuming hydrostatic conditions and linear temperature distribution:
Column 4: Saturation vapor pressure:
Column 5: Moist air density
Column 6: Specific humidity
Column 7: Average specific humidity
|
(1) Elevation |
(2) Temperature |
(3) Pressure |
(4) Vapor Pressure |
(5) Density |
(6) Specific Humidity |
(7) Average Specific Humidity |
(8) Dp/g |
(9) -qv Dp/g |
|
|
(km) |
C |
K |
Pa |
Pa |
kg/m3 |
qv |
kg/m2 |
||
|
0.00 |
30.00 |
303.00 |
101300.00 |
4310.66 |
1.15 |
0.03 |
|||
|
0.02 |
-2126.62 |
44.05 |
|||||||
|
2.00 |
17.00 |
290.00 |
80437.86 |
1934.12 |
0.96 |
0.01 |
|||
|
0.01 |
-1757.16 |
20.10 |
|||||||
|
4.00 |
4.00 |
277.00 |
63200.08 |
804.92 |
0.79 |
0.01 |
|||
|
0.01 |
-1438.96 |
8.50 |
|||||||
|
6.00 |
-9.00 |
264.00 |
49083.90 |
307.27 |
0.65 |
0.00 |
|||
|
0.00 |
-1166.85 |
3.30 |
|||||||
|
8.00 |
-22.00 |
251.00 |
37637.08 |
106.16 |
0.52 |
0.00 |
|||
|
0.00 |
-935.99 |
1.16 |
|||||||
|
10.00 |
-35.00 |
238.00 |
28454.98 |
32.66 |
0.42 |
0.00 |
|||
|
W=77.10 |
|||||||||
W = 77.10 kg/m2 = 77.10 mm