Last updated: 2012-07-17 by David Stepaniak (davestep@ucar.edu)
The 37 standard pressure levels in ERA-Interim in mb (or hPa) are, from highest isobaric altitude to lowest isobaric altitude in the atmosphere:
1, 2, 3, 5, 7, 10, 20, 30, 50, 70, 100, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 775, 800, 825, 850, 875, 900, 925, 950, 975, 1000
This is the ordering convention of the pressure level vertical coordinate in ERA-Interim. ERA pressure level variables are assigned interpolated values where isobaric surfaces dip below topography. There are no missing values. We do not have specific information about the below topography interpolation scheme used by ECMWF at this time.
The 15 standard isentropic (theta) levels in ERA-Interim in K (Kelvin) are, from lowest isentropic altitude to highest isentropic altitude in the atmosphere:
265, 275, 285, 300, 315, [320 PV only], 330, 350, 370, 395, 430, 475, 530, 600, 700, 850
This is the ordering convention of the theta level vertical coordinate in ERA-Interim. Please note that PV (potential vorticity) is archived on an additional isentropic level, namely 320 K. There are no missing values. We do not have specific information about the below topography interpolation scheme used by ECMWF at this time.
For convenience, below we show the ERA-Interim pressure and isentropic levels arranged relative to a standard atmosphere. ERA-Interim pressure levels are shown in bold black digits. ERA-Interim theta levels are shown in bold red digits. Note that the global average tropopause height is indicated ( in blue ~~~) as 12 kilometers in practice the height of the tropopause varies between 8 kilometers (poles) and 17 kilometers (equator). A stratopause ( in green ~~~) at 50 kilometers is also shown, as well as an ozone maximum near 25 kilometers.
For this representation of a standard atmosphere,
potential temperature is computed as
where T is the temperature, po
the reference pressure (1013.25 mb), p the pressure, R the gas constant for dry air
(287.04 J kg-1 K-1), and Cp the specific heat capacity of dry air at
constant pressure (1004.6 J kg-1 K-1).
------------------------------------------------------------------------------------------------------------------- | | | Potential | | Pressure | | Temperature | Height | ERA-I | Temperature | ERA-I | Density meters km feet mi | mb/hPa mb/hPa | K deg C deg F | K K | kg m-3 ------------------------------------- |----------------- |----------------------------- |--------------- |--------- - 80000 --- 80.0 -- 262467 --- 49.7 - | 0.010 -------- | 198.6 ---- -74.5 --- -102.1 | 5350.0 ------- | 0.00002 - 70000 --- 70.0 -- 229659 --- 43.5 - | 0.052 -------- | 219.5 ---- -53.6 --- -64.5 | 3691.6 ------- | 0.00008 - 60000 --- 60.0 -- 196850 --- 37.3 - | 0.220 -------- | 247.0 ---- -26.1 --- -15.0 | 2750.9 ------- | 0.00030 ~ 50000 ~~~ 50.0 ~~ 164042 ~~~ 31.1 ~ | 0.798 ~~~~~~~~ | 270.6 ~~~~ -2.5 ~~~ +27.5 | 2085.5 ~~~~~~~ | 0.00100 ← Ave stratopause 1 - 45000 --- 45.0 -- 147638 --- 28.0 - | 1.491 -------- | 264.1 ---- -9.0 --- +15.8 | 1702.5 ------- | 0.00200 2 - 40000 --- 40.0 -- 131234 --- 24.9 - | 2.871 -------- | 250.3 ---- -22.8 --- -9.0 | 1338.1 ------- | 0.00400 3 5 - 35000 --- 35.0 -- 114829 --- 21.7 - | 5.746 -------- | 236.5 ---- -36.6 --- -33.9 | 1037.0 ------- | 0.00800 7 10 850 - 30000 --- 30.0 -- 98425 --- 18.6 - | 11.970 -------- | 226.5 ---- -46.6 --- -51.9 | 805.3 ------- | 0.01800 20 700- 25000 --- 25.0 -- 82021 --- 15.5 - | 25.492 -------- | 221.5 ---- -51.6 --- -60.9 | 634.5 ------- | 0.04000 ← Ozone maximum
30 600 50 530 - 20000 --- 20.0 -- 65617 --- 12.4 - | 55.293 -------- | 216.6 ---- -56.5 --- -69.7 | 497.3 ------- | 0.08900 - 19000 --- 19.0 -- 62336 --- 11.8 - | 64.674 -------- | 216.6 ---- -56.5 --- -69.7 | 475.6 ------- | 0.10400 70 475 - 18000 --- 18.0 -- 59055 --- 11.2 - | 75.652 -------- | 216.6 ---- -56.5 --- -69.7 | 454.7 ------- | 0.12200 - 17000 --- 17.0 -- 55774 --- 10.6 - | 88.497 -------- | 216.6 ---- -56.5 --- -69.7 | 434.8 ------- | 0.14200 100 430 - 16000 --- 16.0 -- 52493 --- 9.9 - | 103.520 -------- | 216.6 ---- -56.5 --- -69.7 | 415.7 ------- | 0.16600 - 15000 --- 15.0 -- 49213 --- 9.3 - | 121.110 -------- | 216.6 ---- -56.5 --- -69.7 | 397.5 ------- | 0.19500 125 395 - 14000 --- 14.0 -- 45932 --- 8.7 - | 141.700 -------- | 216.6 ---- -56.5 --- -69.7 | 380.1 ------- | 0.22800 150 370 - 13000 --- 13.0 -- 42651 --- 8.1 - | 165.790 -------- | 216.6 ---- -56.5 --- -69.7 | 363.4 ------- | 0.26700 175 350 ~ 12000 ~~~ 12.0 ~~ 39370 ~~~ 7.5 ~ | 193.990 ~~~~~~~~ | 216.6 ~~~~ -56.5 ~~~ -69.7 | 347.4 ~~~~~~~ | 0.31200 ← Ave tropopause 200 225 - 11000 --- 11.0 -- 36089 --- 6.8 - | 226.990 -------- | 216.7 ---- -56.4 --- -69.5 | 332.4 ------- | 0.36500 250 330 - 10000 --- 10.0 -- 32808 --- 6.2 - | 264.990 -------- | 223.2 ---- -49.9 --- -57.8 | 327.5 ------- | 0.41300 - 9500 --- 9.5 -- 31168 --- 5.9 - | 285.840 -------- | 226.5 ---- -46.6 --- -51.9 | 325.2 ------- | 0.44000 300 - 9000 --- 9.0 -- 29528 --- 5.6 - | 308.000 -------- | 229.7 ---- -43.4 --- -46.1 | 322.9 ------- | 0.46700 - 8848 ---
Everest (8848 m, 29028 ft) - 8500 --- 8.5 -- 27887 --- 5.3 - | 331.540 -------- | 232.9 ---- -40.2 --- -40.4 | 320.5 ------- | 0.49600 350 320 PV only - 8000 --- 8.0 -- 26247 --- 5.0 - | 356.510 -------- | 236.2 ---- -36.9 --- -34.4 | 318.4 ------- | 0.52600 - 7500 --- 7.5 -- 24606 --- 4.7 - | 382.990 -------- | 239.4 ---- -33.7 --- -28.7 | 316.2 ------- | 0.55700 400 315 - 7000 --- 7.0 -- 22966 --- 4.3 - | 411.050 -------- | 242.7 ---- -30.4 --- -22.7 | 314.1 ------- | 0.59000 - 6500 --- 6.5 -- 21325 --- 4.0 - | 440.750 -------- | 245.9 ---- -27.2 --- -17.0 | 312.0 ------- | 0.62400 450 - 6000 --- 6.0 -- 19685 --- 3.7 - | 472.170 -------- | 249.1 ---- -24.0 --- -11.2 | 309.9 ------- | 0.66000 500 - 5500 --- 5.5 -- 18045 --- 3.4 - | 505.390 -------- | 252.4 ---- -20.7 --- -5.3 | 308.0 ------- | 0.69700 - 5000 --- 5.0 -- 16404 --- 3.1 - | 540.480 -------- | 255.6 ---- -17.5 --- +0.5 | 305.9 ------- | 0.73600 550 - 4500 --- 4.5 -- 14764 --- 2.8 - | 577.520 -------- | 258.9 ---- -14.2 --- +6.4 | 304.1 ------- | 0.77700 600 - 4000 --- 4.0 -- 13123 --- 2.5 - | 616.600 -------- | 262.1 ---- -11.0 --- +12.2 | 302.1 ------- | 0.81900 650 - 3500 --- 3.5 -- 11483 --- 2.2 - | 657.800 -------- | 265.4 ---- -7.7 --- +18.1 | 300.3 ------- | 0.86300 700 300 - 3000 --- 3.0 -- 9843 --- 1.9 - | 701.210 -------- | 268.6 ---- -4.5 --- +23.9 | 298.4 ------- | 0.90900 - 2500 --- 2.5 -- 8202 --- 1.6 - | 746.910 -------- | 271.9 ---- -1.2 --- +29.8 | 296.7 ------- | 0.95700 750 775 - 2000 --- 2.0 -- 6562 --- 1.2 - | 795.010 -------- | 275.1 ---- +2.0 --- +35.6 | 294.9 ------- | 1.00700 800 825 - 1500 --- 1.5 -- 4921 --- 0.9 - | 845.590 -------- | 278.4 ---- +5.3 --- +41.5 | 293.2 ------- | 1.05800 850 875 - 1000 --- 1.0 -- 3281 --- 0.6 - | 898.760 -------- | 281.6 ---- +8.5 --- +47.3 | 291.5 ------- | 1.11200 900 925 950 - 500 --- 0.5 -- 1640 --- 0.3 - | 954.610 -------- | 284.9 ---- +11.8 --- +53.2 | 289.8 ------- | 1.16700 975 285 1000 - 0 --- 0.0 -- 0 --- 0.0 - |1013.250 -------- | 288.1 ---- +15.0 --- +59.0 | 288.1 ------- | 1.22500 ← Surface 275 265 - -420 ---
Dead Sea (-420 m, -1378 ft) ------------------------------------- |----------------- |----------------------------- |--------------- |---------
Potential temperature is computed as
where T is the temperature, po
the reference pressure (1013.25 mb), p the pressure, R the gas constant for dry air
(287.04 J kg-1 K-1), and Cp the specific heat capacity of dry air at
constant pressure (1004.6 J kg-1 K-1).
Only the simplest complete photochemical cycle for ozone (Chapman cycle) is shown. M represents a third molecule needed to conserve momentum and energy in the recombination of O and O2.
Source of standard atmosphere (height, pressure, temperature, and density): Ahrens, C. Donald, 1994, Meteorology Today, An Introduction to Weather, Climate, and the Environment, Fifth Edition, West Publishing Company, St. Paul (Appendix H).