From: Mapping the risk of avian influenza in wild birds in the US
Variable | Source | Manipulation |
---|---|---|
Binary variable: 1 if the county ever froze, 0 otherwise | ftp://sidads.colorado.edu/pub/DATASETS/NOAA/G02156/metadata/ | Calculated from freeze and thaw date |
Freeze date | ftp://sidads.colorado.edu/pub/DATASETS/NOAA/G02156/metadata/ | Calculated as the first day of the year when more than half of the county was frozen |
Harvested cropland (ha) | None | |
Human population density | The total human population was divided by the area of the county | |
Mean farm size (ha) | None | |
Minimum temperature (°C) | http://www.prism.oregonstate.edu/products/matrix.phtml?year0=2000 | Calculated as the average minimum temperature of all of the 800 m pixels in the county |
Percent family owned farms | None | |
Percent of county in cropland | None | |
Poultry density | http://www.fao.org/geonetwork/srv/en/resources.get?id=12720&fname=glbpo25cor.zip&access=private | The data were aggregated to the county scale and the total number of poultry was divided by the area of the county |
Road density | Calculated as the number roads in each county that connect major population centers | |
Thaw date (°C) | ftp://sidads.colorado.edu/pub/DATASETS/NOAA/G02156/metadata/ | Calculated as the first day of the year when more than half of the county was not frozen |
Total annual precipitation (mm) | http://www.prism.oregonstate.edu/products/matrix.phtml?year0=2000 | Calculated as the average precipitation of all of the 800 m pixels in the county |