Comparison of Monthly and Intramonthly. Indices for the Pacific/North American Teleconnection Pattern

Abstract

Abstract Many applied climatological studies use teleconnection indices to characterize atmospheric flow. Although these indices are often associated with temperature and precipitation patterns, surprisingly little attention has been paid to changes in the flow patterns within the monthly period. This study analyzes the differences between the monthly and intramonthly indices (based on 5-day mean data) for the most important source of winter season low-frequency variability in the midtropospheric geopotential height field over North America, the Pacific/North American (PNA) pattern. Results suggest that the monthly index adequately represents flow patterns at shorter temporal scales. Months with PNA indices suggesting a typical configuration (moderate 700-mb ridging over western North America with moderate troughing in eastern North America) tend to be comprised of days with the same flow, rather than an offsetting of days with amplified ridge-trough and a reversed trough-ridge pattern across North Americ...