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Ogallala Agro-Climate Tool



Version 1.1

The Ogallala Agro-Climate Tool provides estimates of climate statistics, crop evapotranspiration and irrigation demand over the United States' Ogallala aquifer region. The climate statistics reported include probabilities of exceedance of cumulative rainfall and growing degree days, the probability that minimum and maximum daily temperatures will exceed user-defined temperature thresholds, and the probability of heat stress, cold stress and dry periods of varying duration. These statistics are calculated via the aggregation of nearby meteorological station data statistics. Stations can be selected manually or by an expanding radius search algorithm that limits the aggregation to data from nearby stations. As this search algorithm is limited to a 3° longitude by 3° latitude grid centered on the location selected by the user, the application has similar or finer spatial resolution. When statistics are calculated from four or more stations the application presents seasonal climate probability distributions with a statistical resolution of better than 1%. Such distributions can be calculated for arbitrary periods, as seasonal periods can be defined with user-selected beginning and end days. The daily meteorological station data on which the software is based is the most quality-controlled U.S. data available, thus the application provides high resolution and high quality climate information.

The application also displays distributions of crop evapotranspiration for a range of crops derived via the FAO-56 single coefficient crop ET algorithm. These estimates apply to standard conditions as defined by the FAO-56; i.e., crops grown under disease free and optimal soil water conditions, and capable of full production under specified climate conditions. Based on these crop ET estimates and precipitation data from the meteorological database, the application displays probability distributions of the crop's irrigation demand based on a simplified soil water balance equation.

The application is a Visual Basic program that can be run on Windows 98, 2000, and XP operating systems. It should be installed on a PC with a Pentium III or better microprocessor and at least 61 Mbytes of available hard disk space. Monitor screen resolution should be at least 1024 X 768 pixels. Once it is downloaded and installed, information about the application and instructions for it's use can be found by left single-clicking on the 'Help' button on upper left corner. After downloading users are encouraged to report any problems, or make suggestions for changes, by contacting Steven.Mauget@ars.usda.gov.

References

Mauget, S. And G.Leiker,
The Ogallala Agro-Climate Tool
Computers and Electronics in Agriculture
Volume 74, Issue 1, October 2010, Pages 155-162
http://dx.doi.org/10.1016/j.compag.2010.08.002

Last Modified: 04/22/2012