Volume 9, Number 10—October 2003
Research
Environmental Risk and Meningitis Epidemics in Africa
Table 1
Characteristics of the environmental variables
| Variable | Temporal resolution | Time period | Resolution of grid squares | |
|---|---|---|---|---|
| Interpolated meteorologic station dataa |
||||
| Average daily mean absolute humidity |
Mean monthly |
1961–1990 |
0.5° lat x 0.5° long (nominal 50 km) |
|
| Average daily rainfall |
Mean monthly |
1961–1990 |
0.5° lat x 0.5° long (nominal 50 km) |
|
| Remotely sensed satellite datab |
||||
| Average daily aerosol index (dust) |
Mean monthly |
1980–1999 |
1.0° lat x 1.25° long (nominal 100 km) |
|
| Digital maps |
||||
| Land-cover typec |
1992–1993 |
1 x 1 km |
||
| Population densityd | 1990 | 0.042° lat x 0.042° long (nominal 4 km) | ||
aMean monthly climate averages (1961–1990) for absolute humidity and rainfall (the former derived from vapor pressure and mean temperature) were obtained from the Climate Research Unit, University of East Anglia, UK (available from: URL: http://ipcc-ddc.cru.uea.ac.uk/).
bDust was obtained as monthly aerosol index coverages from the U.S. National Aeronautics and Space Administration (NASA), Goddard Space Flight Center, Maryland (available from: URL: http://www.gsfc.nasa.gov/), excluding the period May 1993 to June 1996 for which data are not available.
cLand-cover type was obtained from the USGS NASA PATHFINDER 1km project (available from: URL: http://edcwww.cr.usgs/gov/landdaac/1KM/).
dU.S. Geologic Survey 1990 population density forecasts (available from: URL: http://grid2.cr.usgs.gov/globalpop/africa/).