Organization of Storm Track Anomalies by Recurring Low-Frequency Circulation Anomalies

Abstract

From previous studies it is known that anomalous momentum fluxes by bandpass eddies are important in maintaining long-lasting tropospheric flow anomalies. Evidence is presented that suggests that these anomalous fluxes do not occur at random but happen because the structure of storm track activity is modified by the presence of prominent low-frequency, large-scale circulation anomalies. This behavior is noted in an extended integration of a perpetual January simulation with a general circulation model (GCM). Because nonlinear feedbacks between low- and high-frequency variability make it difficult to establish causal relationships between these two ranges of variability, a model is constructed that approximates the storm track activity that would be expected to accompany a given low frequency without including the feedback of the high frequencies onto the low-frequency state. This model is based on the linearized primitive equations and uses a series of short integrations from random initial condi... Abstract From previous studies it is known that anomalous momentum fluxes by bandpass eddies are important in maintaining long-lasting tropospheric flow anomalies. Evidence is presented that suggests that these anomalous fluxes do not occur at random but happen because the structure of storm track activity is modified by the presence of prominent low-frequency, large-scale circulation anomalies. This behavior is noted in an extended integration of a perpetual January simulation with a general circulation model (GCM). Because nonlinear feedbacks between low- and high-frequency variability make it difficult to establish causal relationships between these two ranges of variability, a model is constructed that approximates the storm track activity that would be expected to accompany a given low frequency without including the feedback of the high frequencies onto the low-frequency state. This model is based on the linearized primitive equations and uses a series of short integrations from random initial condi...