The Influence of Atmospheric Rivers and Associated Latent Heat Release on Downstream Waviness

At any given time, there are four to five atmospheric rivers (ARs) present in the Northern Hemisphere, each with a moisture flux of approximately 1.6 x 10⁸ kg s^-1, comparable to the discharge of the Amazon River into the Atlantic Ocean (Zhu & Newell, 1998). The elevated moisture and low-level winds associated with ARs have been documented to cause heavy rain and flooding events throughout the western United States during the cool season (e.g. Warner et al., 2012). The latent heat released from convection within ARs can alter the tropopause potential vorticity with implications on downstream weather systems and the flow in which they are embedded.

The analysis presented here employs an objective method to identify ARs in the eastern Pacific basin.  The identified ARs are categorized by their associated value of integrated water vapor (IWV), as well as the amount of latent heat release (LHR).  The downstream waviness of the 2 PVU isertel in an appropriate upper-tropospheric isentropic layer is quantified using a metric known as sinuosity. Statistical methods are then applied to determine the relationship between the amount of moisture within the river, the amount of latent heat released, and the “waviness” of the downstream upper-level pattern. It is hypothesized that the latent heat release associated with ARs has a systematic tendency to amplify the downstream wave guide through production of negative tropopause PV anomalies.  The dynamical characteristics of large-scale environments resistant to this tendency are examined.