Influence of the Madden-Julian Oscillation and Caribbean Low-Level Jet on east Pacific easterly waves
Date
2018
Authors
Whitaker, Justin W., author
Maloney, Eric, advisor
Bell, Michael, committee member
Niemann, Jeffrey, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
The east Pacific warm pool exhibits basic state variability associated with the Madden-Julian Oscillation (MJO) and Caribbean Low-Level Jet (CLLJ), which affects the development of easterly waves (EWs). This study compares and contrasts composite changes in the background environment, eddy kinetic energy (EKE) budgets, moisture budgets, and EW tracks during MJO and CLLJ events. While previous studies have shown that the MJO influences jet activity in the east Pacific, the influence of the MJO and CLLJ on EWs is not synonymous. The CLLJ is a stronger modulator of the ITCZ than the MJO, while the MJO has a more expansive influence on the northeastern portion of the basin. Anomalous low-level westerly MJO and CLLJ periods are associated with favorable conditions for EW development paralleling the Central American coast, contrary to previous findings about the relationship of the CLLJ to EWs. Easterly MJO and CLLJ periods support enhanced ITCZ EW development, although the CLLJ is a greater modulator of EW tracks in this region, which is likely associated with stronger moisture and convection variations and their subsequent influence on the EKE budget. ITCZ EW growth during easterly MJO periods is more reliant on barotropic conversion than in strong CLLJ periods, when EAPE to EKE conversion associated with ITCZ convection is more important. Enhanced background state moisture anomalies during strong CLLJ periods lead to stronger diluted CAPE anomalies in the mean state and EWs that support convection. Thus, the influence of these phenomena on east Pacific EWs should be considered distinct.1 1 This abstract is adapted from the abstract of: Whitaker, J.W., and E. D. Maloney, 2018: Influence of the Madden-Julian Oscillation and Caribbean Low-Level Jet on East Pacific Easterly Wave Dynamics. J. Atmos. Sci., in press. ©American Meteorological Society. Used with permission.