Influence of Latitude on the US Great Plains East–West Precipitation Gradient

Precipitation varies greatly from east to west across the US Great Plains. Farmers would have a better means of understanding the applicability of cropping systems research done in one part of the Great Plains to their specific location if they were aware of the rate of change of precipitation with east–west direction at their latitude. The objective of this analysis was to determine if a consistent, predictive relationship exists between the east–west precipitation gradient and latitude in the Great Plains. The east–west precipitation gradient was determined for 15 transects from Texas to North Dakota. The precipitation gradient changed little from 31° N lat. to 38° N lat. and then increased systematically for latitudes further north. A quadratic polynomial relationship fit the data well ( = 0.967) and was used to create a simple spreadsheet decision support tool to help farmers understand how quickly precipitation changes with east–west direction at a given latitude.