This page's content is no longer actively maintained, but the material has been kept on-line for historical purposes.
The page may contain broken links or outdated information, and parts may not function in current web browsers.

Surface Exchange of Methane (Fung et al. 1991)

This page offers access to a number of datasets which describe the exchange of methane between Earth's surface and atmosphere. They have been used in simulations of atmospheric CH4 using the GISS three-dimensional tracer transport model. An overview of the datasets and the model runs is given in Fung et al. (1991) (see References below).

Listed source strengths are global sums from the datasets. In many cases, they are arbitrary values assumed for mathematical convenience. See Fung et al. (1991) for a discussion of the actual source strengths and their uncertainties.

Individual files according to methane source may be downloaded via the following links; All are gzipped ASCII-text tables and none exceed 15-kb in length. All are at 1L×1° resolution.

Alternatively, you may download this entire collection of methane data in one of two ways:

Annual Datasets

Units are kg CH4 / m2 / year.

File Name Description Source Strength
CH4ANIMLS Release from animals; see Lerner et al. (1988) 75.8×109 kg/yr
CH4MSW Release from landfills (municipal solid waste) 44.6×109 kg/yr
CH4GASVENT Release from venting of natural gas at wells 10.3×109 kg/yr
CH4GASLEAK Release from pipeline leakage of natural gas 9.5×109 kg/yr
CH4COAL Release from coal mining 29.2×109 kg/yr
CH4TRMITE Release from termites 20.0×109 kg/yr
CH4HYDV Release from hydrates/clathrates in Soviet Arctic 10.0×109 kg/yr
CH4HYDZ Release from hydrates/clathrates at 76-84°N 10.0×109 kg/yr
CH4SOILABS Loss via soil absorption -25.1×109 kg/yr

Monthly Datasets

Units are kg CH4 / m2 / month.

Name Files Description Source Strength
CH4RICEC JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC
Release from rice cultivation; see Matthews et al. (1991) 79.7×109 kg/yr
CH4WETL JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC
Release from five wetland ecosystems; see Matthews and Fung (1987) 108.8×109 kg/y
CH4BOGS JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC
Release from forested and non-forested bogs; see Matthews and Fung (1987) 30.0×109 kg/yr
CH4SWAMPS JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC
Release from forested and non-forested swamps and alluvial formation; see Matthews and Fung (1987) 39.1×109 kg/yr
CH4TUNDRA JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC
Release from tundra; see Matthews and Fung (1987) 3.2×109 kg/yr
CH4BURN JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC
Release from biomass burning; see Fung et al. (1991) 91.6×109 kg/yr

Reading the Data

A snippet of FORTRAN code like the following can be used to read the ASCII text files.

      PARAMETER (IM=360,JM=180)                                                 
      CHARACTER*80 INFO1, INFO2, INFO3                                          
      INTEGER   IARRAY(IM,JM)                                                   
C                                                                               
                                                                                
      READ(10,910) INFO1                                                        
      READ(10,910) INFO2                                                        
      READ(10,910) INFO3                                                        
      READ(10,920) IARRAY                                                       
C                                                                               
C   CAUTION:  CHECK FOR MISSING AND UNDEFINED VALUES IN IARRAY FIRST,           
C      BEFORE RESCALING AND OPERATING ON THE NUMBERS.   THE VALUES OF           
C      THESE PARAMETERS ARE GIVEN IN INFO1 AND INFO2.                           
C                                                                               
  910 FORMAT (A80)                                                              
  920 FORMAT (10(I8))                                                        
C                                                                               
      STOP                                                                      
      END                                                                       

Explanation of Arrays

In the sample code, four variables are used to store the extracted information: INFO1, INFO2, INFO3, and IARRAY. The first three are character strings which describe the dataset. For example, in the file CH4RICEC.JAN, you will find:

 RICE HARVEST:JAN                        DIMENSION = 360 X 180   SCALE = .1E+08
 OCEAN =   -999999   UNDEF =   9999999   MIN =      10 MAX =   55942
 NUMREC = 6483 (NUMBER OF RECORDS IN DATA FILE)                                 

i.e., they contain the following info:

  • INFO1: A brief identifier of the dataset, the dimensions of array IARRAY, and a scaling factor. In the above example, the scaling factor ".1E+08" means that a value in the array should be divided by 0.1×108 (i.e., 107) to obtain the correct value in kg CH4 / m2 / month.
  • INFO2: Value indicating an oceanic grid point, value indicating "undefined", and minimum and maximum real data values.
  • INFO3: Number of data records in the dataset.

The surface grid IARRAY(I,J) is arranged so that:

  • I = 1 is centered at 179.5°W
  • I increases eastward
  • J = 1 is centered at 89.5°S
  • J increases northward

In other words:

       87S - | - - - | - - - | - - - | - - 
             | (1,3) | (2,3) | (3,3) | 
       88S - | - - - | - - - | - - - | - - 
             | (1,2) | (2,2) | (3,2) | 
       89S - | - - - | - - - | - - - | - - 
             | (1,1) | (2,1) | (3,1) | 
       90S - | - - - | - - - | - - - | - - 
            180W    179W    178W    177W                                        

References

Papers and reports which describe the datasets include: