U.S. Precipitation Variability: Regional Disparities and Multiscale Features Since the 17th Century

Proxy data-based reconstructions provide an essential basis for understanding comprehensive precipitation variability at multiple time scales. This study compared the variation characteristics of reconstructed precipitation data across different regions in the U.S. and the differences at decadal/multidecadal scales. The reconstruction showed that multiple scales of precipitation variability existed in each region and both multidecadal and decadal variability varied over time and across region. There was weaker multidecadal variability in the latter half of the 18th century and during the mid-19th century to mid-20th century east of the Rocky Mountains (RM); however, multidecadal variability appears to have increased since the 20th century in most regions. Decadal variability was weaker west of the RM except in the Southwest U.S. in the latter half of the 18th century. While decadal variability became stronger in the early 20th century, it shifted from a stronger phase to a weaker phase east of the RM. Then, we compared the spatiotemporal differences between the reconstructed Palmer Drought Severity Index (PDSI) and reconstructed precipitation in this study. The reconstructed annual precipitation mostly remains consistent with the existing PDSI dataset, but there are inconsistencies in the severe dry/wet intensities in some regions. Multiscale analysis of regional precipitation data holds great importance for understanding the relationship between precipitation in different regions and the climate system, while also providing a scientific theoretical basis for precipitation prediction.