Submitted to: Water Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2000
Publication Date: January 1, 2000
Interpretive Summary: New atmospheric/climate information has enabled NOAA to produce climate forecasts up to a year in advance. The climate-sensitive agricultural sector can benefit from these climate forecasts by incorporating forecasted regional and local agro-climatic information into long-term agricultural planning and management strategies. To fully exploit emerging climate forecast information, a representative regional precipitation index used t develop agro-climatic information must be identified. To this end the quality of a monthly precipitation index over a large region called a climate division is reviewed. The number of stations used to calculate the precipitation index has changed over the years as a result of station closures, establishment of new stations and change in the selection criteria of the stations. In addition, records at the various stations have occasional gaps resulting from instrument failures or temporary discontinuation of operations. These discontinuities in records may limit the value of the precipitation index for use in the research and development of agro-climatic information. This project quantifies differences in the value of the precipitation index due to discontinuities in station records for a region in Central Oklahoma. The findings demonstrated that the discontinuity in station records does impact the value of the precipitation index and that conclusions that are based on the index, such as climate trends and variability, should be interpreted with the limitations of the precipitation index in mind.
Technical Abstract: New atmospheric/climatic information has enabled the National Weather Service to produce climate outlooks up to a year in advance. To fully exploit emerging climate outlook information for long-term agricultural planning and management strategies, a representative regional climate index that is at the same scale as te climate outlooks and that can be used to develop agro-climatic information must be identified. To this end, the monthly precipitation index for the climate divisions, as published by the National Climatic Data Center (NCDC), is reviewed. In this paper, the approximation errors due to the discontinuities in station records are quantified for the NDCD precipitation index of the central climate division of Oklahoma. In a first analysis, the monthly precipitation data sent from which the index is calculated is artificially altered to mimic instrument failures and station discontinuities by randonly removing a number of months from the data set. Instrument failure and station discontinuities are mimicked by randomly removing 10% of the monthly data. The differences between the two calculated monthly precipitation indices range from 1 to 4% of the mean monthly precipitation, and from 1 to 7% of the mean temporal variations of the monthly precipitation. In a second analysis the monthly precipitation index is compared directly to the NCDC precipitation and from 9 to 24% of their mean temporal variations. These values demonstrate that the discontinuities in station records of the NCDC divisional precipitation index can be relevant and that research results should be interpreted with consideration to the approximation errors introduced by discontinuities in station records.