Understanding the Role of Cloud and Convective Processes in Simulating the Weaker Tropical Cyclones over Indian Seas

Abstract

This study addresses the problem of incorporating moist processes (resolving the grid scale and parameterizing the subgrid scale) at resolutions of 9 and 3 km with double-and triplenested domains, respectively, in predicting the track and intensity of four cases of weaker tropical cyclones over the North Indian Ocean. The sensitivity experiments are carried out with three convective parameterization schemes, and the results are evaluated based on the track and intensity of cyclones. The Betts-MillerJanjic scheme shows the most reasonable representation of track and intensity and therefore is used for all sensitivity experiments related to microphysical schemes in two and three domains. Three sets of microphysics sensitivity experiments are carried out: The first set includes experiments with parameterized moist convection (referred to as the 9-km experiment) in two domains (27 and 9 km). The second and third sets of simulation experiments are carried out at 9 km in two domains (27 and 9 km; referred to as the 9-km-noCP) and at 3 km in three domains (27 km, 9 km and 3 km; referred to as the 3-km experiment), respectively, by resolving the grid-scale convection explicitly with the four bulk microphysical schemes. The explicit moist convection treatment at 9-and 3-km resolution produces a better cyclone simulation than the parameterized convection at 9-km resolution. The latent heat released in the generation of hydrometeors such as snow and graupel in the mid-tropospheric levels appears to influence the heating within the inner core of the cyclone. The comparable and more realistic representation of mid-tropospheric heating is possibly one of the main reasons behind the improvement at 9-km-noCP and 3 km. The stronger vertical advection of moist static energy gives wellorganized mesoscale convection within the cyclone environment at 9-km-noCP and 3-km resolution. This study therefore demonstrates the importance of microphysical processes in the simulation of weaker TC over the North Indian Ocean.

Impact of physical parameterization schemes on track and intensity of severe cyclonic storms in Bay of Bengal

“…These weak cyclones, due to their slow motion and quasi-stationary feature, cause very heavy rainfall and in turn large amount of damage to the property. Kanase et al (2014) suggested that convective adjustment scheme such as BMJ works better for relatively weak intensity storms. Mandal et al (2004) in their sensitivity study for two BoB cyclones using MM5 model, have shown that GD or BMJ works better in simulating track and intensity of cyclones.…”

“…Very few studies have focused on simulating the weak intensity storms (Osuri et al 2013;Srinivas et al 2013, Kanase et al 2014), but the detailed reasoning behind the success or failure of physical parameterization is hardly addressed. Further, it is essential to know which factor has more impact on cyclone's intensity.…”

Sensitivity of Microphysical Schemes on the Simulation of Post-Monsoon Tropical Cyclones over the North Indian Ocean

“…The schemes which showed rapid intensification process during the model simulation showed minimum deviation from the observed track, whereas the schemes which showed a slower intensification process during the model simulation showed maximum deviation from the observed track [45]. The intensity of the TC cyclone is influenced by the auto conversion process between the hydrometers and the amount of latent heat released during the conversion process [46,47]. To assess the impact of various microphysical schemes on the intensity of TCs, the vertical profile of the area averaged mixing ratios was calculated at every 3-hour interval over the entire numerical domain.…”

“…Therefore, the WSM3 scheme produced a higher intensity for the cyclones Nilofar, Daye, Kyant, and Phethai. The intensity of the TC cyclone is influenced by the auto conversion process between the hydrometers and the amount of latent heat released during the conversion process [46,47]. To assess the impact of various microphysical schemes on the intensity of TCs, the vertical profile of the area averaged mixing ratios was calculated at every 3-hour interval over the entire numerical domain.…”

Understanding the characteristics of microphysical processes in the rapid intensity changes of tropical cyclones over the Bay of Bengal

“…The aforementioned studies indicated that the distribution of MP processes/hydrometeors plays a critical role in cyclone intensification, including rapid intensity changes and their dependency on moisture availability. However, various sensitivity studies are available over the NIO that focus on the overall track and intensity simulation and its relation with MP processes over the BoB region (Deshpande et al ., 2012; Kanase et al ., 2015; Maw and Min, 2017; Chutia et al ., 2019; Mohan et al ., 2019). Most studies conclude that the TC track is relatively insensitive to MP processes, but there is likely a distinct impact on the intensity simulations as outlined in recent studies.…”