Radiative and Microphysical Impacts of the Saharan Dust on Two Concurrent Tropical Cyclones: Danielle and Earl (2010)

Saharan dust exerts profound impacts on the genesis and intensification of tropical cyclones (TCs). Such impacts on various stages of the TCs have yet to be explored. In this study, we utilize the Cloud-Resolving weather research and forecasting model (WRF) to investigate the relative importance of the microphysical and radiative effects of dust on two hurricanes (Earl and Danielle) at different life stages under similar dynamical conditions in 2010. Both TCs were embedded in a dusty environment throughout their lifetime. A new dust ice nucleation scheme was implemented into the aerosol-aware Texas A&M University two-moment microphysical scheme in WRF. Moreover, the dust radiative effect was included in the Goddard Shortwave Scheme of WRF. Our sensitivity experiments show that the radiative effect of dust (DRAD) amplified the mid-level ridge in the Central Atlantic Ocean through temperature perturbation, changing the tracks of Danielle and Earl. Further analyses reveal an early shift of Danielle's maximum intensity for 12 hours but a significantly suppressed Earl in DRAD. In addition, the microphysical effect of dust had little impact on the large-scale dynamical fields and storm tracks. The inclusion of dust as ice nucleation particles results in more variations in the intensity of Danielle and Earl than in other scenarios. This is owing to the higher maximum diabatic heating rate in the rainband region that perturbs the size of the TC. This study shows the dominant dust radiative effects on both intensity and track of the storm. In addition, there is evidence that dust suppresses the early stage TC but provides favorable conditions for matured TC. Both findings have profound implications for hurricane forecast and address the importance of accounting for detailed cloud microphysics and aerosol-TC interactions in the operational forecasting models. This modeling study assesses how dust from the Saharan Desert affects tropical cyclones (TCs). Dust modifies the radiative transfer by reflecting and absorbing sunlight (the radiative effect) and hence the environmental temperature profile. In addition, dust also changes cloud processes (the dust microphysical effect) that perturbs the cloud distribution. A cloud-resolving model was used to assess the dust impacts on two TCs at different development stages, that is, Danielle and Earl (2010). We found that the radiative effect of dust plays an important role in the intensity and path of both TCs. Specifically, the radiative effects of dust weakened the early stage TC Earl, resulted in an early shift of maximum intensity of the matured TC Danielle, and perturbed the path of both TCs. The dust microphysics effect, on the other hand, had little impact on the TC environment and its path but induced larger variations in the intensity of both TCs. This study reveals that dust exhibits distinct effects depending on the stage of the TC development, showing that dust suppresses the early stage TC but provides favorable conditions for the matured TC. A dust-related ice nucleating scheme and radiation parameterizations were implemented in the aerosol-aware weather research and forecasting modelThe radiative effect of dust plays a larger role in the large-scale environment and intensity of tropical cyclones (TCs) than the microphysical effectThe dust effect suppresses the early stage TC but provides favorable conditions for matured TC