ARS | Publication request: CLIMATE DIVISION INDEX AND OBSERVED MONTHLY PRECIPITATION

Submitted to: Annual American Geophysical Union Hydrology Days
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 1999
Publication Date: May 1, 1999

Technical Abstract: To fully exploit emerging climate outlook information for agricultural application, the relation between the regional climate index and precipitation at a location must be quantified. In a first analysis the monthly precipitation for climate divisions is reviewed to establish the reliability and consistency of the record for long term trend analyses. Over the years the number of stations used to calculate the index has changed and records at various stations have occasional gaps. To quantify the influences of these discontinuities, the NCDC precipitation index is compared to the average time series of twelve stations. Differences are about 10% of the actual precipitation values and about 17% of the temporal variability, which demonstrates that discontinuities in station records can have a relevant impact on the divisional climate index value. In a second analysis, the time series of the twelve stations are used to quantify the spatial variability of the precipitation signal within a climate division. The spatial variability is given as the differences between the standardized values of the divisional precipitation index and at-a-station observations. The variability with the central deviation with 94% of the differences with -1 to +1 standard deviations and extremes near three standard deviations. Average monthly differences are 0.22 standard deviations in December and 0.44 in June-July during the findings of this project help in the interpretation of divisional precipitation outlooks to establish the range and uncertainties of corresponding local precipitation values.