Grid Systems

(1) GEIA Grid System

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GEIA (Global Emission Inventory Activities) Grid is a grid system with 1° by 1° latitude/longitude resolution (Figure 1), and a standard grid system used by GEIA, a component of the International Global Atmospheric Chemistry (IGAC) core project of the International Geosphere - Biosphere Program (IGBP).

Definition of GEIA Grid Code:

 GEIA Grid Code = (j*1000) + i

where

j: row number starting at 1 for 90°S to 89°S latitude, to 180 for 89°N to 90°N latitude;

i: column number starting at 1 for 180°W to 179°W longitude, to 360 for 179°E to 180°E longitude.

The latitude(lat) and longitude(long) of the centre of each grid cell can be calculated from the Grid Code as

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lat = (j-91) + 0.5

long = (i-181) + 0.5

Figure 2 gives an example of the latitude and longitude of the center of the GEIA grid cell 1001.

(2) GloPeRD Grid System

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The GloPeRD grid system is based on the GEIA grid system and NAPAP (National Acid Precipitation Assessment Program) grid system (Air and Energy Engineering Research Laboratory, 1989), and made up of grid cells with 1/6 degree latitude by 1/4 degree longitude (approximately 20 x 20 km). The GloPeRD Grid Code consists two parts: GEIA Grid Code and Sub-GloPeRD Grid Code.

GloPeRD Grid number = GEIA Grid Code*100 + Sub-GloPeRD Grid Code

where

Sub-GloPeRD Grid Code = l*10 + k      (l:1 - 6; k : 1 – 4)

There are 24 Sub-GloPeRD Grid cells in each GEIA Grid cell, and the definition of Sub-GloPeRD Grid number is given in Figure 3.

The latitude and longitude of the center of each GloPeRD grid cell with GloPeRD Grid Code = [(j*1000) + i]*100 + l*10+k are given by

[View] (D)

Figure 4 gives the latitude and longitude of the center of the GloPeRD grid cell 100111.

References:

Air and Energy Engineering Research Laboratory, "The 1985 NAPAP Emissions Inventory (Version 2): Development of the Annual Data and Modelers’ Tapes", Prepared for the National Acid Precipitation Assessment Program, EPA-600/7-89-012a, November 1989, Research Triangle Park, NC 27711

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