Convective Instability Associated with the Eastward-Propagating Rainfall Episodes over Eastern China during the Warm Season

• Published in: Journal of climate Vol. 27; no. 6; pp. 2331 - 2339
• Main Authors: Chen, Guixing, Yoshida, Ryuhei, Sha, Weiming, Iwasaki, Toshiki, Qin, Huiling
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 15-03-2014
• Subjects: Advection; Anomalies; Atmospheric moisture; Climate cycles; Convection; Convection cooling; Convective available potential energy; Convective instability; Convective zone; Cooling; Diurnal cycle; Diurnal variations; Earth, ocean, space; Estimates; Exact sciences and technology; External geophysics; Foothills; General circulation models; Growth stage; Horizontal advection; Instability; Low-level jets; Mesoscale phenomena; Meteorology; Nocturnal; Nocturnal cooling; Potential energy; Precipitation; Propagation; Rain; Rainfall; Rainfall forecasting; Seasons; Stability; Studies; Warm seasons; Water in the atmosphere (humidity, clouds, evaporation, precipitation); Eastern China; Far East; Asia; China; Tibetan Plateau; China, People's Rep; rainfall; Available potential energy; atmospheric precipitation; Mesoscale convective system; Space remote sensing; Propagation characteristic; Observation data; Satellite observation; Reanalysis; energy balance; Convective instability; TRMM satellite
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/JCLI-D-13-00443.1

Analysis of the latest satellite rainfall and reanalysis datasets from 1998 to 2012 demonstrates that eastward-propagating rainfall episodes, which typically occur in late night and morning, are determinant factors for the rainfall diurnal cycle and climate anomalies over eastern China. The episode growth and propagation are facilitated by an elevated layer of conditionally unstable air in a mesoscale zone at their eastern leading edge. The convective available potential energy (CAPE), despite convection consumption and nocturnal cooling, decreases only from a high value to a moderate one during episode duration. An estimate of the CAPE generation budget suggests that low-level horizontal advection and vertical lifting of the warm moist air can produce sufficient CAPE to balance other stabilization effects, sustaining the mesoscale maximum of convective instability ahead of rainfall episodes. These instability geneses are pronounced at the convection growth stage and linked closely to a mesoscale nocturnal low-level jet. Thus, a proper representation of them in forecast models is essential for improved prediction of the warm-season rainfall.