An analysis of northern hemisphere block sizes compared to climatology and seasonal variations

Abstract

The goal of the following research was to discover if any trends exist between the size of large-scale, mid-latitude anticyclonic events and seasonal characteristics. A 20-year analysis of North American blocking events was compiled by calculating the mean size of each event using NCEP-NCAR analyses and a simplified Rossby wave equation. Blocking events were identified using block definitions from previous studies and retrieved from the University of Missouri-Columbia blocking database. The sizes of blocking events were then compared to Northern Hemisphere climatological information derived in previous research. Block sizes were compared to El Niño- Southern Oscillation, blocking intensity as defined by Wiedenmann et al. 2002, and other seasonal characteristics. Results will assist researchers and long-range forecasters to predict the scale and potential impacts of blocking events, of which onset and duration are currently difficult to forecast.