RELIABILITY OF 3-MONTH PRECIPITATION FORECASTS FOR USE IN GRAZING LANDS MANAGEMENT

Authors: Schneider, Jeanne; Garbrecht, Jurgen; ROSSEL, FREDERIC - USDA

Submitted to: Proceedings of the National Conference on Grazing Lands
Publication Type: Proceedings
Publication Acceptance Date: 12/5/2000
Publication Date: 12/5/2000
Citation: N/A

Interpretive Summary: Seasonal climate forecasts prepared by NOAA are available covering the coming year, predicting shifts in total precipitation and average temperature over three-month periods. Forecast skill is still modest, but sufficient to present an opportunity to change decision-making in agriculture and natural resource management from a reactive mode to a proactive mode. There have been problems with application of these climat forecasts, some related to the unusual form of the forecasts (statements of probability). Also, information on the reliability of the forecasts on a regional basis has not been available. Both of these problems are addressed by the development of an application-specific forecast skill score for precipitation, which is used to evalute the reliability of climate forecasts over each forecast division in the contiguous United States, and to associate risks with possible forecast outcomes. Using this sskill score, we find that reliability varies significantly from region to region. However, a sufficient level of reliability exists in some regions so that managers of grazing lands could use the climate forecasts of precipitation to project forage quality and quantity, assess susceptibility of forages to disease and insect outbreaks, define optimal application rates of fertilizers, manage animals in preparation for inclement weather, and anticipate erosion problems.

Technical Abstract: The National Oceanic and Atmospheric Administration's Climate Prediction Center (NOAA/CPC) produces climate forecasts that predict total precipitation over three-month periods out to a year in advance. Average forecast reliability is still modest, but sufficient to present an opportunity for consideration in decision-making in grazing lands management. Our research objective is to address the challenges associate with assessing, adapting, and applying these climate forecasts to agriculture and natural resource management. In this study the reliability of the 3-month precipitation forecast at the shortest lead time was examined for all CPC forecast divisions in the contiguous United States. The period of study was from 1995 through 1999. Precipitation climate forecasts were compared with actual precipitation totals for 58 overlapping 3-month periods in the 5-year study interval. A skill score was developed to assess forecast reliability for a given forecast division, and was used to support assignments of risk to future forecasts. Using this skill score, reliability varies significantly from region to region. However, the results of this comparison suggest that a sufficient level of reliability exists in the 3-month precipitation forecasts to exploit or mitigate the impact of expected variations of precipitation in some regions of the United States. Managers of grazing lands could use reliable climate forecasts of precipitation to project forage quality and quantity, assess susceptibility of forages to disease and insect outbreaks, define optimal application rates of fertilizers, manage animals in preparation for inclement weather, and anticipate erosion problems.