Estimating precipitation normals for USCRN stations

Normals estimation in this study is based on the fact that monthly precipitation anomalies at any target location are similar to those of neighboring stations. This analysis evaluated several variations of estimation approaches. The best method was one that included the use of monthly departure data from ~11 neighboring stations (within ~78 km of the target station), and a weighting scheme that used the inverse square difference in monthly precipitation totals between the neighboring and target station. Normals were then generated for USCRN sites using data from USCRN stations and neighboring COOP stations. When the estimated normals are based on the use of a few years of data, their errors are about 13-18% of the “typical” anomalies. This suggests that these estimated USCRN normals can be useful in climate monitoring and assessment.