Affiliation:
1. Department of Atmospheric Sciences School of Environmental Studies China University of Geosciences Wuhan China
2. Centre for Severe Weather and Climate and Hydro‐geological Hazards Wuhan China
3. Key Laboratory of Cloud‐Precipitation Physics and Severe Storms Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China
4. University of Chinese Academy of Sciences Beijing China
Abstract
AbstractThis study investigates how the asymmetric inner‐core convection can modulate midlevel ventilation preceding rapid intensification (RI) of sheared tropical cyclones (TC) based on two numerical experiments of Typhoon Lekima (2019) with warm (CTL) and relatively cool (SSTA0) sea surface temperatures (SSTs). The midlevel ventilation is dominated by an inflow layer between heights of 5 and 10 km in the upshear‐left quadrant, while the convective development in the upshear‐left quadrant acts to induce asymmetric midlevel outflow. These outflows, together with the reduced tilt, lessen the strength of midlevel inflow in a quadrant‐mean sense. Due to a slower boundary‐layer recovery of low‐entropy air over cooler SST, convective development in the upshear‐left quadrant in SSTA0 is suppressed, causing stronger midlevel inflows than that in CTL. A backward trajectory analysis initialized near the RI onset of CTL shows that the TC in CTL is less susceptible to the intrusion of midlevel dry air from left‐of‐shear and upshear‐left quadrant due to the weaker upshear‐left midlevel inflow. Moreover, the intruding air parcels in SSTA0 tend to originate farther away from TC center and lower the eyewall equivalent potential temperature more effectively. A column‐integrated moist static energy (MSE) budget reveals a dramatic increase in MSE in inner‐core region associated with the positive changes of horizontal MSE advection radially outward of enhanced convective rainbands preceding RI onset in CTL. In contrast, the MSE increases more slowly in SSTA0 due to the weaker upshear convection, inducing a less favorable thermodynamic conditions that is potentially responsible for a delayed RI onset.
Funder
China University of Geosciences
National Natural Science Foundation of China
Publisher
American Geophysical Union (AGU)
Subject
Space and Planetary Science,Earth and Planetary Sciences (miscellaneous),Atmospheric Science,Geophysics