| The circulation associated with atmospheric teleconnections has profound effects on the climate of the midwestern United States. Previous studies have investigated the upper-level airflow associated with different teleconnection patterns, but the variation of low-level airflow has not been studied. Analyses of the association of low-level airflow and atmospheric teleconnections are presented for an example location in the lower peninsula of Michigan. Air-parcel trajectories, which provide an important approach to monitoring changes in atmospheric circulation, are used to represent the low-level circulation. A five-day back-trajectory climatology was developed using an isobaric (constant-pressure) model, for the 925 hPa surface, from the four-times daily National Centers for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) reanalysis data. Methodological issues addressed include the spatial and temporal resolution of the trajectories, as well as the effective use of a Geographic Information System (GIS) to display and analyze the trajectory patterns. The climatologies developed here will help delineate potential regions where advection of heat and/or moisture can be expected during particular times of the year and will also illustrate the patterns in circulation associated with atmospheric teleconnections, both of which are important for medium to long-range weather forecasting. |
