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ISLSCP II EDGAR 3 Gridded Greenhouse and Ozone Precursor Gas Emissions
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File Name Convention
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There are 2 data files witrh this data set:

edgar_variable_data_1d_YYYY.csv

where:
edgar          identifies the data set.
Variable      identifies the particular gas emissions contained in the file:
                   ch4  = CH4, methane
                   co   = CO, carbon monoxide
                   co2  = CO2, carbon dioxide
                   n2o  = N2O, nitrous oxide
                   nmv  = NMVOC (Non-Methane Volatile Organic Compounds)
                   nox  = NO2, nitrogen dioxide
                   so2  = SO2, sulphur dioxide
data            identifies that this is tabular data (as opposed to the "map" 
                   files below).
1d               identifies the spatial resolution of the data set: 1d is 
                  "1 degree".
YYYY        is the four-digit year: 1970, 1980, 1990, or 1995.
lto               identifies a file that includes emissions at less than 1,000 m 
                  (landing and take-off phases of aircraft operations; files
                   without lto do not include this data).
.csv             is the extension, indicating the format of the tables as 
                   "comma-separated values".

The ISLSCP II staff also used the coordinates given in the original tabular 
data to create two-dimensional ASCII map files for each gas on a 1.0 by 1.0 degree 
Earth grid. These files are named in a similar fashion as the table names 
given above except that they contain the word "map" as opposed to the word 
"data" and the file extension is ".asc" indicating that this is an ASCII map. 
As an example, the file named "edgar_co2_map_1d_1980.asc" contains the CO2 
anthropogenic emissions for 1980 mapped onto a 1 degree grid and is based on 
data from the original data table named "edgar_co2_data_1d_1980.csv".

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ASCII File Format
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All of the files in the ISLSCP Initiative II data collection are in the ESRI ArcGIS ASCII, or text format. 

The file format for the "mapped" files consists of numerical fields of varying 
length, which are delimited by a single space and arranged in columns and rows. 
The files each contain 360 columns by 180 rows. All values in these files are 
written as real numbers. No distinction is made for cells with no emissions 
over water or land (i.e. value=0).

 WARNING: The 1.0 x 1.0 degree map product is for browse use only. These data files 
 were created from the original 1.0 x 1.0 degree tabular data. 

The map files are all gridded to a common equal-angle lat/long grid, where the 
coordinates of the upper left corner of the files are located at 180 degrees 
West, 90 degrees North and the lower right corner coordinates are located at 
180 degrees East, 90 degrees South. Data in the files are ordered from North to 
South and from West to East beginning at 180 degrees West and 90 degrees North.