GEOS–Chem v9–02 Online User's Guide
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Appendix 3: GEOS–Chem Vertical Grids
We compare the vertical grids of the meteorological data that GEOS–Chem reads from disk.
A3.1 Comparison of GCAP, GEOS–3, GEOS–4, and GEOS–5/GEOS–FP/MERRA vertical grids
GCAP, GEOS–3, GEOS–4, and GEOS–5 vertical levels, up to 3 km
(Solid lines are edges, dotted lines are centers)
GCAP, GEOS–3, GEOS–4, and GEOS–5 vertical levels, up to 10 km
GCAP, GEOS–3, GEOS–4, and GEOS–5 vertical levels, up to 32 km
GCAP, GEOS–3, GEOS–4, and GEOS–5 vertical levels, up to 80 km
The native vertical resolution of the GCAP meteorological fields (which come from the GISS–II GCM) is 23 hybrid sigma-pressure levels, extending from the surface up to 0.002 hPa.
We computed the pressures and altitudes listed below assuming a surface pressure of 1013.25 hPa. Altitudes are approximations based on the US Standard Atmosphere. This shall suffice for purposes of illustration.
GCAP Native Vertical Grid (23 layers)
L Sig Edge Sig Mid Altitude Pressure
(unitless) (unitless) (km) (hPa)
========================================================
0.000000 89.247 0.002
23 0.000000 77.507 0.017
0.000000 73.489 0.031
22 0.000000 66.346 0.088
0.000000 62.725 0.145
21 0.000000 57.209 0.303
0.000000 54.014 0.461
20 0.000000 48.400 0.960
0.000000 45.215 1.460
19 0.000000 39.712 3.045
0.000000 36.651 4.630
18 0.000000 33.388 7.315
0.000000 31.209 10.000
17 0.000000 28.959 13.900
0.000000 27.300 17.800
16 0.000000 25.141 24.700
0.000000 23.543 31.600
15 0.000000 21.439 43.900
0.000000 19.876 56.200
14 0.000000 18.387 71.200
0.000000 17.187 86.200
13 0.000000 16.154 101.600
0.000000 15.265 117.000
12 0.000000 14.431 133.500
0.000000 13.690 150.000
11 0.000000 12.825 171.737
0.000000 12.056 193.473
10 0.000000 11.192 220.903
0.000000 10.421 248.332
9 0.000000 9.524 284.042
0.000000 8.721 319.752
8 0.000000 7.580 377.198
0.000000 6.578 434.645
7 0.000000 5.424 509.687
0.000000 4.401 584.730
6 0.000000 3.509 657.185
0.000000 2.692 729.641
5 0.000000 2.098 786.052
0.000000 1.536 842.463
4 0.000000 1.215 876.103
0.000000 0.903 909.743
3 0.000000 0.692 933.032
0.000000 0.485 956.321
2 0.000000 0.344 972.365
0.000000 0.206 988.408
1 0.000000 0.099 1000.829
0.000000 -0.006 1013.250
The native vertical resolution of GEOS–4 meteorological fields is 55 hybrid eta levels, extending from the surface up to 0.01 hPa. The first 14 levels from the surface upward are pure sigma levels; the rest are fixed pressure levels.
To conserve memory, you have the option of running GEOS–Chem a reduced vertical resolution of 30 eta levels. GEOS–Chem will combine eta levels above ~50 hPa on-the-fly.
We computed the pressures and altitudes listed below assuming a surface pressure of 1013.25 hPa. Altitudes are approximations based on the US Standard Atmosphere. This shall suffice for purposes of illustration.
A3.3.1 GEOS–4 native vertical grid
GEOS-4 Native Vertical Grid (55 hybrid pressure-sigma layers)
L Eta Edge Eta Mid Altitude Pressure
(unitless) (unitless) (km) (hPa)
========================================================
0.000000 80.581 0.010
55 0.000005 78.146 0.015
0.000010 76.357 0.020
54 0.000016 74.594 0.026
0.000022 73.180 0.033
53 0.000030 71.812 0.040
0.000037 70.657 0.048
52 0.000046 69.440 0.057
0.000055 68.392 0.066
51 0.000067 67.243 0.078
0.000078 66.245 0.089
50 0.000093 65.115 0.105
0.000108 64.130 0.120
49 0.000128 63.004 0.140
0.000148 62.021 0.159
48 0.000173 60.902 0.185
0.000199 59.924 0.211
47 0.000232 58.816 0.245
0.000265 57.846 0.279
46 0.000308 56.752 0.322
0.000350 55.794 0.365
45 0.000405 54.717 0.420
0.000460 53.773 0.476
44 0.000529 52.716 0.546
0.000599 51.788 0.617
43 0.000687 50.754 0.706
0.000775 49.844 0.795
42 0.000886 48.835 0.907
0.000996 47.946 1.019
41 0.001135 46.962 1.160
0.001274 46.092 1.301
40 0.001446 45.134 1.476
0.001619 44.286 1.651
39 0.001834 43.355 1.868
0.002048 42.529 2.085
38 0.002312 41.627 2.353
0.002576 40.825 2.620
37 0.002900 39.951 2.948
0.003224 39.173 3.276
36 0.003619 38.328 3.677
0.004013 37.574 4.077
35 0.004492 36.759 4.562
0.004971 36.030 5.047
34 0.005548 35.244 5.632
0.006126 34.539 6.217
33 0.006818 33.782 6.918
0.007510 33.101 7.620
32 0.008336 32.372 8.456
0.009162 31.716 9.293
31 0.010141 31.015 10.285
0.011120 30.383 11.277
30 0.012287 29.701 12.460
0.013455 29.085 13.643
29 0.014844 28.423 15.050
0.016232 27.824 16.457
28 0.017878 27.180 18.124
0.019523 26.596 19.792
27 0.021467 25.971 21.761
0.023410 25.402 23.730
26 0.025699 24.794 26.049
0.027987 24.240 28.368
25 0.030673 23.648 31.089
0.033358 23.108 33.810
24 0.036499 22.531 36.993
0.039641 22.004 40.175
23 0.043326 21.438 43.910
0.047012 20.920 47.644
22 0.051326 20.364 52.016
0.055641 19.855 56.388
21 0.060682 19.309 61.496
0.065723 18.807 66.603
20 0.071600 18.269 72.558
0.077477 17.773 78.512
19 0.084313 17.243 85.439
0.091149 16.753 92.366
18 0.099191 16.222 100.515
0.107234 15.731 108.663
17 0.116695 15.198 118.250
0.126157 14.706 127.837
16 0.137287 14.170 139.115
0.148418 13.674 150.393
15 0.161513 13.134 163.661
0.174608 12.633 176.930
14 0.190061 12.086 192.587
0.205513 11.578 208.244
13 0.223772 11.021 226.745
0.242032 10.504 245.246
12 0.263587 9.936 267.087
0.285142 9.409 288.927
11 0.310561 8.830 314.683
0.335980 8.291 340.439
10 0.365938 7.700 370.793
0.395895 7.148 401.146
9 0.431179 6.541 436.898
0.466464 5.975 472.650
8 0.508017 5.351 514.754
0.549571 4.768 556.857
7 0.598479 4.125 606.413
0.647387 3.523 655.968
6 0.695218 2.969 704.433
0.743050 2.443 752.898
5 0.786601 1.986 797.026
0.830152 1.549 841.154
4 0.866492 1.197 877.974
0.902831 0.857 914.795
3 0.929330 0.615 941.644
0.955828 0.378 968.494
2 0.970469 0.249 983.328
0.985110 0.122 998.163
1 0.992555 0.058 1005.706
1.000000 -0.006 1013.250
A3.3.2 GEOS–4 reduced vertical grid
GEOS–4 Reduced Vertical Grid (30 hybrid pressure-sigma layers
L Eta Edge Eta Mid Altitude Pressure
(unitless) (unitless) (km) (hPa)
========================================================
0.000000 80.581 0.010
30 0.000028 72.180 0.038
0.000055 68.392 0.066
29 0.000127 63.053 0.139
0.000199 59.924 0.211
28 0.000399 54.834 0.414
0.000599 51.788 0.617
27 0.001109 47.135 1.134
0.001619 44.286 1.651
26 0.002816 40.166 2.864
0.004013 37.574 4.077
25 0.006588 34.024 6.685
0.009162 31.716 9.293
24 0.014342 28.654 14.542
0.019523 26.596 19.792
23 0.023755 25.307 24.080
0.027987 24.240 28.368
22 0.033814 23.020 34.272
0.039641 22.004 40.175
21 0.047641 20.836 48.282
0.055641 19.855 56.388
20 0.066559 18.727 67.450
0.077477 17.773 78.512
19 0.084313 17.243 85.439
0.091149 16.753 92.366
18 0.099191 16.222 100.515
0.107234 15.731 108.663
17 0.116695 15.198 118.250
0.126157 14.706 127.837
16 0.137287 14.170 139.115
0.148418 13.674 150.393
15 0.161513 13.134 163.661
0.174608 12.633 176.930
14 0.190061 12.086 192.587
0.205513 11.578 208.244
13 0.223772 11.021 226.745
0.242032 10.504 245.246
12 0.263587 9.936 267.087
0.285142 9.409 288.927
11 0.310561 8.830 314.683
0.335980 8.291 340.439
10 0.365938 7.700 370.793
0.395895 7.148 401.146
9 0.431179 6.541 436.898
0.466464 5.975 472.650
8 0.508017 5.351 514.754
0.549571 4.768 556.857
7 0.598479 4.125 606.413
0.647387 3.523 655.968
6 0.695218 2.969 704.433
0.743050 2.443 752.898
5 0.786601 1.986 797.026
0.830152 1.549 841.154
4 0.866492 1.197 877.974
0.902831 0.857 914.795
3 0.929330 0.615 941.644
0.955828 0.378 968.494
2 0.970469 0.249 983.328
0.985110 0.122 998.163
1 0.992555 0.058 1005.706
1.000000 -0.006 1013.250
The native vertical resolution of GEOS–5 meteorological fields is 72 hybrid eta levels, extending from the surface up to 0.01 hPa. The first 31 levels from the surface upward are pure sigma levels; the rest are fixed pressure levels.
In order to minimize the amount of memory, you can run GEOS–Chem with a reduced vertical resolution of 47 eta levels. This option combines eta levels above ~80 hPa.
We computed the pressures and altitudes listed below assuming a surface pressure of 1013.25 hPa. Altitudes are approximations based on the US Standard Atmosphere. This shall suffice for purposes of illustration.
A3.4.1 GEOS–5 native vertical grid
GEOS-5 Native Vertical Grid (72 hybrid pressure-sigma levels)
L Eta Edge Eta Mid Altitude Pressure
(unitless) (unitless) (km) (hPa)
========================================================
0.000000 80.581 0.010
72 0.000005 78.146 0.015
0.000010 76.357 0.020
71 0.000016 74.594 0.026
0.000022 73.180 0.033
70 0.000030 71.812 0.040
0.000037 70.657 0.048
69 0.000046 69.440 0.057
0.000055 68.392 0.066
68 0.000067 67.243 0.078
0.000078 66.245 0.089
67 0.000093 65.115 0.105
0.000108 64.130 0.120
66 0.000128 63.004 0.140
0.000148 62.021 0.159
65 0.000173 60.902 0.185
0.000199 59.924 0.211
64 0.000232 58.816 0.245
0.000265 57.846 0.279
63 0.000308 56.752 0.322
0.000350 55.794 0.365
62 0.000405 54.717 0.420
0.000460 53.773 0.476
61 0.000529 52.716 0.546
0.000599 51.788 0.617
60 0.000687 50.754 0.706
0.000775 49.844 0.795
59 0.000886 48.835 0.907
0.000996 47.946 1.019
58 0.001135 46.962 1.160
0.001274 46.092 1.301
57 0.001446 45.134 1.476
0.001619 44.286 1.651
56 0.001834 43.355 1.868
0.002048 42.529 2.085
55 0.002312 41.627 2.353
0.002576 40.825 2.620
54 0.002900 39.951 2.948
0.003224 39.173 3.276
53 0.003619 38.328 3.677
0.004013 37.574 4.077
52 0.004492 36.759 4.562
0.004971 36.030 5.047
51 0.005548 35.244 5.632
0.006126 34.539 6.217
50 0.006818 33.782 6.918
0.007510 33.101 7.620
49 0.008336 32.372 8.456
0.009162 31.716 9.293
48 0.010141 31.015 10.285
0.011120 30.382 11.277
47 0.012287 29.701 12.460
0.013455 29.085 13.643
46 0.014844 28.423 15.050
0.016232 27.824 16.457
45 0.017878 27.180 18.124
0.019523 26.596 19.792
44 0.021467 25.971 21.761
0.023410 25.402 23.730
43 0.025699 24.794 26.049
0.027987 24.240 28.368
42 0.030673 23.648 31.089
0.033358 23.108 33.810
41 0.036499 22.531 36.993
0.039641 22.004 40.175
40 0.043326 21.438 43.910
0.047011 20.920 47.644
39 0.051326 20.364 52.016
0.055641 19.855 56.388
38 0.060682 19.309 61.496
0.065723 18.807 66.603
37 0.071600 18.269 72.558
0.077477 17.773 78.512
36 0.084313 17.243 85.439
0.091149 16.753 92.366
35 0.099191 16.222 100.514
0.107233 15.731 108.663
34 0.116695 15.198 118.250
0.126157 14.706 127.837
33 0.137287 14.170 139.115
0.148418 13.674 150.393
32 0.161513 13.134 163.661
0.174608 12.633 176.930
31 0.190061 12.086 192.587
0.205513 11.578 208.244
30 0.223772 11.021 226.745
0.242032 10.504 245.246
29 0.263587 9.936 267.087
0.285142 9.409 288.927
28 0.309854 8.846 313.966
0.334566 8.320 339.005
27 0.353349 7.943 358.038
0.372133 7.582 377.070
26 0.390927 7.237 396.112
0.409720 6.905 415.155
25 0.428528 6.585 434.212
0.447337 6.277 453.269
24 0.466153 5.980 472.335
0.484970 5.692 491.401
23 0.503795 5.413 510.475
0.522620 5.142 529.550
22 0.541449 4.879 548.628
0.560278 4.623 567.706
21 0.579115 4.375 586.793
0.597953 4.132 605.880
20 0.616790 3.896 624.967
0.635628 3.665 644.054
19 0.654471 3.439 663.146
0.673314 3.219 682.239
18 0.685878 3.074 694.969
0.698442 2.932 707.699
17 0.711006 2.792 720.429
0.723570 2.654 733.160
16 0.736134 2.517 745.890
0.748698 2.382 758.621
15 0.761265 2.249 771.354
0.773832 2.118 784.088
14 0.786400 1.988 796.822
0.798967 1.860 809.556
13 0.809021 1.759 819.743
0.819075 1.659 829.929
12 0.826616 1.584 837.570
0.834157 1.510 845.211
11 0.841698 1.436 852.852
0.849239 1.363 860.493
10 0.856781 1.290 868.135
0.864323 1.218 875.776
9 0.871864 1.146 883.418
0.879406 1.075 891.059
8 0.886948 1.004 898.701
0.894489 0.934 906.342
7 0.902031 0.864 913.984
0.909573 0.795 921.626
6 0.917116 0.726 929.268
0.924658 0.657 936.911
5 0.932200 0.589 944.553
0.939743 0.521 952.195
4 0.947285 0.454 959.837
0.954828 0.387 967.480
3 0.962370 0.320 975.122
0.969913 0.254 982.765
2 0.977456 0.189 990.408
0.984999 0.123 998.051
1 0.992500 0.058 1005.650
1.000000 -0.006 1013.250
A3.4.2 GEOS–5 reduced vertical grid
GEOS-5 Reduced Vertical Grid (47 hybrid pressure-sigma levels)
L Eta Edge Eta Mid Altitude Pressure
(unitless) (unitless) (km) (hPa)
========================================================
0.000000 80.581 0.010
47 0.000028 72.180 0.038
0.000055 68.392 0.066
46 0.000127 63.053 0.139
0.000199 59.924 0.211
45 0.000399 54.834 0.414
0.000599 51.788 0.617
44 0.001109 47.135 1.134
0.001619 44.286 1.651
43 0.002816 40.166 2.864
0.004013 37.574 4.077
42 0.006588 34.024 6.685
0.009162 31.716 9.293
41 0.014342 28.654 14.542
0.019523 26.596 19.792
40 0.023755 25.307 24.080
0.027987 24.240 28.368
39 0.033814 23.020 34.272
0.039641 22.004 40.175
38 0.047641 20.836 48.282
0.055641 19.855 56.388
37 0.066559 18.727 67.450
0.077477 17.773 78.512
36 0.084313 17.243 85.439
0.091149 16.753 92.366
35 0.099191 16.222 100.514
0.107233 15.731 108.663
34 0.116695 15.198 118.250
0.126157 14.706 127.837
33 0.137287 14.170 139.115
0.148418 13.674 150.393
32 0.161513 13.134 163.661
0.174608 12.633 176.930
31 0.190061 12.086 192.587
0.205513 11.578 208.244
30 0.223772 11.021 226.745
0.242032 10.504 245.246
29 0.263587 9.936 267.087
0.285142 9.409 288.927
28 0.309854 8.846 313.966
0.334566 8.320 339.005
27 0.353349 7.943 358.038
0.372133 7.582 377.070
26 0.390927 7.237 396.112
0.409720 6.905 415.155
25 0.428528 6.585 434.212
0.447337 6.277 453.269
24 0.466153 5.980 472.335
0.484970 5.692 491.401
23 0.503795 5.413 510.475
0.522620 5.142 529.550
22 0.541449 4.879 548.628
0.560278 4.623 567.706
21 0.579115 4.375 586.793
0.597953 4.132 605.880
20 0.616790 3.896 624.967
0.635628 3.665 644.054
19 0.654471 3.439 663.146
0.673314 3.219 682.239
18 0.685878 3.074 694.969
0.698442 2.932 707.699
17 0.711006 2.792 720.429
0.723570 2.654 733.160
16 0.736134 2.517 745.890
0.748698 2.382 758.621
15 0.761265 2.249 771.354
0.773832 2.118 784.088
14 0.786400 1.988 796.822
0.798967 1.860 809.556
13 0.809021 1.759 819.743
0.819075 1.659 829.929
12 0.826616 1.584 837.570
0.834157 1.510 845.211
11 0.841698 1.436 852.852
0.849239 1.363 860.493
10 0.856781 1.290 868.135
0.864323 1.218 875.776
9 0.871864 1.146 883.418
0.879406 1.075 891.059
8 0.886948 1.004 898.701
0.894489 0.934 906.342
7 0.902031 0.864 913.984
0.909573 0.795 921.626
6 0.917116 0.726 929.268
0.924658 0.657 936.911
5 0.932200 0.589 944.553
0.939743 0.521 952.195
4 0.947285 0.454 959.837
0.954828 0.387 967.480
3 0.962370 0.320 975.122
0.969913 0.254 982.765
2 0.977456 0.189 990.408
0.984999 0.123 998.051
1 0.992500 0.058 1005.650
1.000000 -0.006 1013.250
MERRA is not a new data product, but a 30-year reanalysis done with the GMAO GEOS–5 GCM (version 5.2.0). For more information, please see our MERRA page on the GEOS–Chem wiki.
In the vertical, the MERRA meteorological fields have 72 hybrid eta levels, extending from the surface up to 0.01 hPa. The first 31 levels from the surface upward are pure sigma levels; the rest are fixed pressure levels.
To conserve memory, you have the option of running GEOS–Chem with a reduced vertical resolution of 47 eta levels. GEOS–Chem will combine eta levels above ~80 hPa on-the-fly.
A3.5.1 MERRA native vertical grid
The native vertical resolution of the MERRA meteorological fields is identical to the GEOS–5 72-layer native grid.
A3.5.2 MERRA reduced vertical grid
The reduced vertical resolution of the MERRA meteorological fields is identical to the GEOS–5 47-layer reduced grid.
GMAO recently released its GEOS–FP meteorological data product, which has ultrafine horizontal resolution (0.25° x 0.3125°). For more information, please see our GEOS–FP page on the GEOS–Chem wiki.
In the vertical, the GEOS–FP meteorological fields have 72 hybrid eta levels, extending from the surface up to 0.01 hPa. The first 31 levels from the surface upward are pure sigma levels; the rest are fixed pressure levels.
To conserve memory, you have the option of running GEOS–Chem with a reduced vertical resolution of 47 eta levels. GEOS–Chem will combine eta levels above ~80 hPa on-the-fly.
A3.6.1 GEOS–FP native vertical grid
The native vertical resolution of the GEOS–FP meteorological fields is identical to the GEOS–5 72-layer native grid.
A3.6.2 GEOS–FP reduced vertical grid
The reduced vertical resolution of the GEOS–FP meteorological fields is identical to the GEOS–5 47-layer reduced grid.