MANDATORY PRESSURE LEVELS
<
Level |
Remarks |
Temp.
Range |
Critical Thickness For Snow |
Standard
Height
Above Sea level |
1000 mb |
|
|
|
0 meters |
0
feet |
925 mb |
|
|
|
750 to 800 meters |
2460 to 2624 ft |
850 mb |
Besides the surface, 850mb is used to calculate temperature advection.
Also used in weather forecasting to determine high temperature on sunny,
warm days and also used to determine maximum wind gust on sunny,
well-mixed days. |
0 to + 40 in summer
-40 to +20 in
winter |
1000 to 850 = 1300 meters
850 to 700 = 1540 meters |
1500 meters |
4921 ft |
700 mb |
The "free atmosphere" begins here. This pressure level skims the
tops of the Rockies, so, for practical purposes, there is little ground
about this level. The last mandatory level in the lower troposphere |
-15 to +15 in summer
-40 to +5 in
winter |
1000 to 700 = 2840 meters |
3000 meters |
9842 ft |
500 mb |
This pressure marks the approximate level where half the weight of the
local air column is below and half the weight is above. Thus, 500mb
is considered to represent the middle troposphere |
-25 to 0 in summer
-45 to -10 in
winter |
1000 to 500 meters = 5400 meters |
5500 meters |
18044 ft |
400 mb |
The approximate level where winds steer well-developed hurricanes.
The first mandatory level in the upper troposphere |
|
|
7000 meters |
22965 ft |
300 mb |
The pressure level near the cruising altitude of most commercial aircraft.
The approximate pressure at the summit of Mount Everest. |
-55 to -35
(marginal seasonal changes) |
|
9000 meters |
29527 ft |
250 mb |
The typical pressure level of the jet stream over the middle latitudes. |
|
|
10500 meters |
34448 ft |
200 mb |
The typical pressure level of the tropopause over the middle latitudes. |
-60 to -45
(marginal seasonal changes) |
|
12000 meters |
39370 ft |
150 mb |
|
|
|
13500 meters |
44291 ft |
|