Reconstruction of Late-18th Century Upper-air Circulation Using Forensic Synoptic Analysis

Abstract

In this study I attempt to develop an outline of the general atmospheric flow around the time of 1785 C.E., in North America. The results of my reconstruction of daily weather in the year 1785 in the northeastern part of North America imply a relatively cold flow over central and eastern North America for most of the year (McNally, 2004). The source of the colder air is to the north and west, and I begin with the assumption that a north to northwest flow from north central Canada was prevalent for most of the year. By comparing proxy data from other locations around the world to identify the location of the polar front (or edge of the polar cell), it is possible to outline a general flow around the northern hemisphere resulting in one similar to that theorized by Lamb (1977), and described as a “short-circuit cross-polar” flow, around the edge of a displaced and possibly larger polar cell.