A Synoptic–Dynamic Model of Subseasonal Atmospheric Variability

Abstract

A global synoptic?dynamic model (GSDM) of subseasonal variability is proposed to provide a framework for real-time weather?climate monitoring and to assist with the preparation of medium-range (e.g., week 1?3) predictions. The GSDM is used with a regional focus over North America during northern winter. A case study introduces the time scales of the GSDM and illustrates two circulation transitions related to eastward-moving wave energy signals and their connection to remote tropical forcing. Global and zonal atmospheric angular momentum (AAM) is used to help define the synoptic evolution of the GSDM components and to link regional synoptic variations with physical processes like the global mountain and frictional torque. The core of the GSDM consists of four stages based on the Madden?Julian oscillation (MJO) recurrence time. Additionally, extratropical behaviors including teleconnection patterns, baroclinic life cycles, and ?monthly oscillations provide intermediate and fast time scales that are combined with the quasi-oscillatory (30?70 day) MJO to define multiple time-/space-scale linear relationships. A unique feature of the GSDM is its focus on global and regional circulation transitions and the related extreme weather events during periods of large global AAM tendency.