The Sensitivity of Eyewall Replacement Cycles to Shortwave Radiation

Abstract

The sensitivity of tropical cyclone secondary eyewall formation (SEF) and subsequent eyewall replacement cycles (ERCs) to shortwave radiation is examined in this study by varying the solar constant and diurnal cycle at different times prior to an ERC using idealized simulations from the Weather Research and Forecasting model. The magnitude of shortwave radiation plays an important role in modifying the timing of the SEF with nonlinear interactions amplifying the SEF formation differences at longer lead-times. Shortwave radiation has a delaying effect on the SEF and ERC primarily through its modifications of the distribution of convective and stratiform heating profiles in the rainbands. Shortwave radiation reduces both the area and diabatic heating of convection in the model domain, while increasing the amount of stratiform precipitation that has weaker low-level cooling and upper-level heating rates. The primary mechanism by which shortwave radiation reduces the diabatic heating profile and frequency of convection in the rainbands is through heating of the mid-upper troposphere which stabilizes the region and reduces convective available potential energy.

Cloud‐Radiation Feedback Facilitates Secondary Eyewall Formation of Tropical Cyclones

“…However, the ridding of the incloud‐warming still slows down the development of stratiform precipitation and decreased its coverage in the outer‐core region (Figure 11b). The delayed and weakened stratiform precipitation causes delayed SEF, which is similar to the results of Trabing and Bell (2021). The comparison between CTRL and NRAD60 further confirming that the development of stratiform precipitation associated with ORBs is the key dynamic process of CRF affecting SEF.…”

“…Radiation has profound influences on rainband convection and SEF, which is an important topic in TC dynamics. Previous studies revealed the multifaceted roles of shortwave radiation on the SEF (Tang et al., 2017; Trabing & Bell, 2021). This study probes into the horizontal heterogeneous distribution of radiative heating (mainly longwave) between the cloudy and the cloud‐free region (i.e., CRF) on SEF.…”

“…Specifically, Tang et al (2017) found that the shortwave radiation is crucial in the SEF of Hurricane Edouard (2014) by suppressing convection in the moat region. However, Trabing and Bell (2021) pointed out that shortwave radiation suppresses SEF by reducing the extent and magnitude of diabatic heating in convective rainbands using a set of idealized simulations. Although there is discrepancy on whether shortwave radiation is favorable for SEF which may due to the difference between real case and idealized study and different region they focused, they both stressed that shortwave radiation is an important factor affecting SEF.…”

“…Among all the environmental forcings, radiation also has profound influences on convection in TC (e.g., Ruppert & O'Neill, 2019;Trabing et al, 2019;Xu & Randall, 1995). By far, studies discussing the influence of radiation on SEF are concentrated on shortwave radiation (Tang et al, 2017;Trabing & Bell, 2021). Specifically, Tang et al (2017) found that the shortwave radiation is crucial in the SEF of Hurricane Edouard (2014) by suppressing convection in the moat region.…”