Upscale Feedback of Tropical Synoptic Variability to Intraseasonal Oscillations through the Nonlinear Rectification of the Surface Latent Heat Flux*
نویسندگان
چکیده
Analysis of observational data suggests two-way interactions between the tropical intraseasonal oscillation (ISO) and synoptic-scale variability (SSV). On one hand, SSV is strongly modulated by the ISO; that is, a strengthened (weakened) SSV appears during the enhanced (suppressed) ISO phase. The northwest– southeast-oriented synoptic wave train is strengthened and well organized in the northwestern Pacific during the enhanced ISO phase but weakened during the suppressed ISO phase. On the other hand, SSV may exert an upscale feedback to ISO through the nonlinearly rectified surface latent heat flux (LHF). The maximum synoptic contribution exceeds 20%–30% of the total intraseasonal LHF over the tropical Indian Ocean, western Pacific, and northeastern Pacific. The nonlinearly rectified LHF leads the ISO convection and boundary layer specific humidity, and thus it may contribute to the propagation of the ISO in boreal summer through the preconditioning of the surface moisture and moist static energy ahead of the convection.
منابع مشابه
A multiscale model for tropical intraseasonal oscillations.
The tropical intraseasonal 40- to 50-day oscillation (TIO) is the dominant component of variability in the tropical atmosphere with remarkable planetary-scale circulation generated as envelopes of complex multiscale processes. A new multiscale model is developed here that clearly demonstrates the fashion in which planetary-scale circulations sharing many features in common with the observationa...
متن کاملSurface fluxes and tropical intraseasonal variability: a reassessment
The authors argue for the hypothesis that interactive feedbacks involving surface enthalpy fluxes are important to the dynamics of tropical intraseasonal variability. These include cloud-radiative feedbacks as well as surface turbulent flux feedbacks; the former effectively act to transport enthalpy from the ocean to the atmosphere, as do the latter. Evidence in favor of this hypothesis include...
متن کاملNew Multiscale Models and Self-Similarity in Tropical Convection
One of the unexplained striking features of tropical convection is the observed statistical self-similarity, in clusters, superclusters, and intraseasonal oscillations through complex multi-scale processes ranging from the mesoscales to the equatorial synoptic scales to the intraseasonal/planetary scales. Here new multi-spatial scale, multi-time scale, simplified asymptotic models are derived s...
متن کاملThe skeleton of tropical intraseasonal oscillations.
The Madden-Julian oscillation (MJO) is the dominant mode of variability in the tropical atmosphere on intraseasonal timescales and planetary spatial scales. Despite the primary importance of the MJO and the decades of research progress since its original discovery, a generally accepted theory for its essential mechanisms has remained elusive. Here, we present a minimal dynamical model for the M...
متن کاملVariations of Sensible and Latent Heat Fluxes from a Great Lakes Buoy and Associated Synoptic Weather Patterns
An investigation of sensible and latent heat fluxes and their relation to synoptic weather events was performed using hourly meteorological measurements from National Data Buoy Center buoy 45003, located in northern Lake Huron, during April–November of 1984. Two temporal heat flux regimes were found to exist over Lake Huron. The first period extended from April through July and was characterize...
متن کامل