Diurnal Radiation Cycle Impact in Different Stages of Hurricane Edouard (2014)

Abstract:

This work examines the impact of diurnally varying radiation cycle on the intensity, structure and track of Hurricane Edouard (2014) at different stages of its life cycle through convection-permitting simulations.During the formation stage, nighttime destabilization through radiative cooling may promote deep moist convection that eventually leads to the genesis of the storm while a tropical cyclone fails to develop in the absence of the night phase despite a strong incipient vortex under favorable environmental conditions. The nighttime radiative cooling further enhances the primary vortex before the storm undergoes rapid intensification (RI). Thereafter, the nighttime radiative cooling mainly increases convective activities outside of the primary eyewall that leads to stronger/broader outer rainbands and larger storm size during the mature stage of the hurricane but there is little impact on the hurricane intensity in terms of maximum surface wind speed. There is no apparent eyewall replacement cycle (ERC) simulated in both sensitivity experiments without the diurnal cycle (daytime only and nighttime only) while the control forecast undergoes secondary eyewall formation during the mature stage of Edourad (as observed), suggesting the potential role of the diurnally varying radiative impact. Through changing the strength of the initial vortex during the formation stage, the diurnal cycle may also alter the track of the storm.