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Banded Convective Activity Associated With Mesoscale Gravity Waves Over Southern China
Author(s) -
Du Yu,
Zhang Fuqing
Publication year - 2019
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2018jd029523
Subject(s) - gravity wave , convection , wavelength , mesoscale meteorology , geology , mesoscale convective system , geophysics , internal wave , infragravity wave , convective available potential energy , gravitational wave , mechanics , tropical wave , atmospheric duct , atmospheric sciences , wave propagation , longitudinal wave , physics , mechanical wave , climatology , meteorology , optics , atmosphere (unit) , astrophysics
Banded convective activity that occurred near the south coast of China on 30 January 2018 was investigated through convection‐allowing simulations using a nonhydrostatic mesoscale model. The simulations capture reasonably well the observed characteristics of this event. The convective bands are found to be closely related to an episode of mesoscale gravity waves propagating northeastward with a wave speed of around 12 m/s and a primary wavelength of about ~40–50 km. Further analyses and sensitivity experiments reveal that the environment provides a wave duct for these gravity waves, with a thick low‐level stable layer below 850 hPa capped by a low‐stability reflecting layer with a critical level. The strength and depth of the low‐level stable layer determine the intrinsic phase speed and wavelength of the ducted gravity waves. In the sensitivity tests that the stable layer depth is reduced, the wave characteristics change according to what are predicted with the wave duct theory. The convective bands collocate and propagate in phase with the peak updraft regions of the gravity waves, suggesting strong interactions of convection and gravity waves, in which the ducted gravity waves can trigger and modulate convection, while latent heating from convection enhances the waves. In essence, both wave ducting and wave‐convection interaction are jointly responsible for the banded convective activity.