Ohio River Valley winter moisture conditions associated with the Pacific-North American teleconnection pattern

摘要

The relationship between the Pacific-North American (PNA) teleconnection pattern and Ohio River Valley (ORV) winter precipitation and hydrology is described. The PNA is significantly linked to moisture var-iability in an area extending from southeastern Missouri, northeastward over states adjacent to the Ohio River through Ohio. Maximum correlation between the PNA index and station precipitation peaks in southern Indiana at r = -0.71, making the circulation/climate teleconnection one of the strongest in the Northern Hemisphere. The North Pacific index (NPI), a Pacific basin sea level pressure index that is highly correlated to the PNA, confirms a strong circulation-ORV precipitation relationship extending back to 1899. In contrast, measures such as the Tahiti-Darwin Southern Oscillation index (SOI) and Nino-3.4 (5 deg S-5 deg N, 120 deg -170 deg W) sea temperatures are not significantly correlated to ORV winter precipitation. Wettest (driest) winters occur with zonal (meridional) flow with the PNA negative (positive) and North Pacific sea level pressure anomalously high (low). Moisture flux convergence extends much farther north from the Gulf of Mexico in the wet winters, compared to dry, and excess of precipitation over evaporation (moisture budget) is over 100 mm larger throughout much of the ORV. Wet winters, particularly those of 1949 and 1950 changed the ORV hydrology to one of extensive wet conditions, as measured by the Palmer hydrologic drought index (PHDI). Unusually dry winters, however, appear to have less impact on the index; many ORV climate divisions remain moist through the winter despite low precipitation. Winter mean streamflow along the Ohio River and its tributaries varies significantly between PNA extremes, with river discharges up to 100 percent higher in PNA-negative winters as opposed to PNA-positive winters.