Olson land map

On this page we discuss the land map from Jennifer Olson that is currently used by the GEOS-Chem Dry deposition and Soil NOx emissions modules.

Overview

Description of land map

The GEOS-Chem Dry deposition and Soil NOx emissions modules rely on the Olson (1992) land map. This map specifies 74 different land types on the 0.5° x 0.5° "generic" grid, which is defined by:

Lon centers = -179.75, -179.25, -178.75, -178.25, ... 178.25, 178.75, 179.25, 179.75
Lat centers =  -89.75,  -89.25,  -88.75,  -88.25, ...  88.25,  88.75,  89.25,  89.75

The individual Olson land types and their respective indices are as follows:

  0 Water              25 Deciduous           50 Desert
  1 Urban              26 Deciduous           51 Desert
  2 Shrub              27 Conifer             52 Steppe
  3 ---                28 Dwarf forest        53 Tundra
  4 ---                29 Trop. broadleaf     54 rainforest
  5 ---                30 Agricultural        55 mixed wood/open
  6 Trop. evergreen    31 Agricultural        56 mixed wood/open
  7 ---                32 Dec. woodland       57 mixed wood/open
  8 Desert             33 Trop. rainforest    58 mixed wood/open
  9 ---                34 ---                 59 mixed wood/open
 10 ---                35 ---                 60 conifers
 11 ---                36 Rice paddies        61 conifers
 12 ---                37 agric               62 conifers
 13 ---                38 agric               63 Wooded tundra
 14 ---                39 agric.              64 Moor
 15 ---                40 shrub/grass         65 coastal
 16 Scrub              41 shrub/grass         66 coastal
 17 Ice                42 shrub/grass         67 coastal
 18 ---                43 shrub/grass         68 coastal
 19 ---                44 shrub/grass         69 desert
 20 Conifer            45 wetland             70 ice
 21 Conifer            46 scrub               71 salt flats
 22 Conifer            47 scrub               72 wetland
 23 Conifer/Deciduous  48 scrub               73 water
 24 Deciduous/Conifer  49 scrub

Here is a plot of the Olson 1992 land map at 0.5° x 0.5° resolution.

--Bob Y. 15:56, 21 March 2012 (EDT)

Preparation of input files for GEOS-Chem

The raw Olson land map data are stored in the file owe14d.0.5 (which is now archived in Bob Yantosca's disk space). This was an ASCII file containing 20 integer values per line (Fortran format '(20i4)').

To prepare the Olson land map for input into GEOS-Chem, one used the IDL routine REGRIDH_LAI (which is distributed as part of the GAMAP package in the subdirectory gamap2/regridding/regridh_lai.pro. REGRIDH_LAI read the following files as input:

1. owe14d.0.5: Olson land map file at 0.5° x 0.5° resolution
2. lai_all.dat: leaf area index data at 1° x 1° resolution

and would create the following files as output:

1. vegtype.global: Olson land map indices, on the GEOS-Chem grid
2. laiMM.global: leaf area index files, on the GEOS-Chem grid (MM = 01 .. 12)

REGRIDH_LAI was called several times to create a vegtype.global file for each different GEOS-Chem grid (4° x 5°, 2° x 2.5°, and the 0.5° x 0.666° nested grids).

NOTE: The original leaf area index data has now been supplanted by those from the MODIS satellite instrument.

References

1. Bey I., D. J. Jacob, R. M. Yantosca, J. A. Logan, B. Field, A. M. Fiore, Q. Li, H. Liu, L. J. Mickley, and M. Schultz, Global modeling of tropospheric chemistry with assimilated meteorology: Model description and evaluation, J. Geophys. Res., 106, 23,073-23,096, 2001
2. Olson, J, World Ecosystems (WE1.4): Digital raster data on a 10 minute geographic 1080 x 2160 grid, in Global Ecosystems Database, version 1.0, Disc A, edited by NOAA Natl. Geophys. Data Center, Boulder, Colorado, 1992.
3. Wang, Y., D.J. Jacob, and J.A. Logan, Global simulation of tropospheric O3-NOx-hydrocarbon chemistry, 1. Model formulation, J. Geophys. Res., 103, D9, 10,713-10,726, 1998.