Impact of Tropical Cyclones on Inhabited Areas of the SWIO Basin at Present and Future Horizons. Part 1: Overview and Observing Component of the Research Project RENOVRISK-CYCLONE

Bousquet, Olivier; Barruol, Guilhem; Cordier, Emmanuel; Barthe, Christelle; Bielli, Soline; Calmer, Radiance; Rindraharisaona, Elisa J.; Roberts, Grégory; Tulet, Pierre; Amélie, Vincent; Fleischer‐Dogley, Frauke; Mavume, Alberto; Zucule, Jonas; Zakariasy, Lova; Razafindradina, Bruno; Bonnardot, François; Singh, Manvendra; Lees, Édouard; Durand, Jonathan; Mékies, Dominique; Claeys, M.; Pianezze, Joris; Thompson, Callum; Tsai, Chia‐Lun; Husson, Romain; Mouche, Alexis; Ciccione, Stéphane; Cattiaux, Julien; Chauvin, Fabrice; Marquestaut, Nicolas

doi:10.3390/atmos12050544

Cited by 16 publications

(27 citation statements)

References 119 publications

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“…The objective of this study, conducted as part of the ReNovRisk-Cyclone research programme [21] is to further evaluate the benefit of 1D vs. 3D ocean coupling for tropical cyclone modeling. It is based on numerical simulations of tropical cyclone Bejisa, which passed nearby Reunion Island in January 2014 and has been one of the main research focus of ReNovRisk-Cyclone [22,23]. To achieve this objective, we use a high resolution numerical modeling system based on the coupling of the atmospheric model Meso-NH [24] and a regional configuration of the ocean model NEMO [25].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Atmosphere-Ocean Coupling on the Structure and Intensity of Tropical Cyclone Bejisa in the Southwest Indian Ocean

et al. 2021

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A set of numerical simulations is relied upon to evaluate the impact of air-sea interactions on the behaviour of tropical cyclone (TC) Bejisa (2014), using various configurations of the coupled ocean-atmosphere numerical system Meso-NH-NEMO. Uncoupled (SST constant) as well as 1D (use of a 1D ocean mixed layer) and 3D (full 3D ocean) coupled experiments are conducted to evaluate the impact of the oceanic response and dynamic processes, with emphasis on the simulated structure and intensity of TC Bejisa. Although the three experiments are shown to properly capture the track of the tropical cyclone, the intensity and the spatial distribution of the sea surface cooling show strong differences from one coupled experiment to another. In the 1D experiment, sea surface cooling (∼1 ∘C) is reduced by a factor 2 with respect to observations and appears restricted to the depth of the ocean mixed layer. Cooling is maximized along the right-hand side of the TC track, in apparent disagreement with satellite-derived sea surface temperature observations. In the 3D experiment, surface cooling of up to 2.5 ∘C is simulated along the left hand side of the TC track, which shows more consistency with observations both in terms of intensity and spatial structure. In-depth cooling is also shown to extend to a much deeper depth, with a secondary maximum of nearly 1.5 ∘C simulated near 250 m. With respect to the uncoupled experiment, heat fluxes are reduced from about 20% in both 1D and 3D coupling configurations. The tropical cyclone intensity in terms of occurrence of 10-m TC wind is globally reduced in both cases by about 10%. 3D-coupling tends to asymmetrize winds aloft with little impact on intensity but rather a modification of the secondary circulation, resulting in a slight change in structure.

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Section: Introductionmentioning

confidence: 99%

The Effect of Atmosphere-Ocean Coupling on the Structure and Intensity of Tropical Cyclone Bejisa in the Southwest Indian Ocean

et al. 2021

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“…In this regard, observations of clouds and precipitation in Reunion Island will continue to be reinforced in the frame of ACTRIS through the deployment, in late 2021, of a second, volumetric (i.e., 360 • scanning), BASTA cloud radar at the Maïdo observatory. A transportable polarimetric X-band radar, aiming at complementing observations provided by Reunion Island's two operational S-band weather radar systems, will also be installed at Saint-Joseph (southern part of the island) in September 2021, in the frame of the Interreg-V Indian Ocean research project ESPOIRS ("Etude des Systèmes Precipitant de l'Océan Indien par Radars et Satellites" [41]). The deployment of this additional cloud radar, together with the enhancement of the ground-based weather radar network, will allow for further, long-term, studies of the seasonal and inter-annual variability of tropical clouds, but also to benefit from multi-frequency radar observations to better understand the formation and life cycle of clouds and precipitation over this unique tropical area.…”

Section: Discussionmentioning

confidence: 99%

Cloud Radar Observations of Diurnal and Seasonal Cloudiness over Reunion Island

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In November 2016, a 95 GHz cloud radar was permanently deployed in Reunion Island to investigate the vertical distribution of tropical clouds and monitor the temporal variability of cloudiness in the frame of the pan-European research infrastructure Aerosol, Clouds and Trace gases Research InfraStructure (ACTRIS). In the present study, reflectivity observations collected during the two first years of operation (2016–2018) of this vertically pointing cloud radar are relied upon to investigate the diurnal and seasonal cycle of cloudiness in the northern part of this island. During the wet season (December–March), cloudiness is particularly pronounced between 1–3 km above sea level (with a frequency of cloud occurrence of 45% between 12:00–19:00 LST) and 8–12 km (with a frequency of cloud occurrence of 15% between 14:00–19:00 LST). During the dry season (June–September), this bimodal vertical mode is no longer observed and the vertical cloud extension is essentially limited to a height of 3 km due to both the drop-in humidity resulting from the northward migration of the ITCZ and the capping effect of the trade winds inversion. The frequency of cloud occurrence is at its maximum between 13:00–18:00 LST, with a probability of 35% at 15 LST near an altitude of 2 km. The analysis of global navigation satellite system (GNSS)-derived weather data also shows that the diurnal cycle of low- (1–3 km) and mid-to-high level (5–10 km) clouds is strongly correlated with the diurnal evolution of tropospheric humidity, suggesting that additional moisture is advected towards the island by the sea breeze regime. The detailed analysis of cloudiness observations collected during the four seasons sampled in 2017 and 2018 also shows substantial differences between the two years, possibly associated with a strong positive Indian Ocean Southern Dipole (IOSD) event extending throughout the year 2017.

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“…The objective of this section is to illustrate the OWA coupled system and its modularity and the consistence of the models and physical parameterizations. Several observational data obtained in the framework of the RNR-CYC program [15] are used to validate the coupled model. The best-track database from RSMC La Réunion is used to evaluate the track and intensity of each modelled TC.…”

Section: Some Examples Of Coupled Ocean-atmosphere Modeling Of Tcs In the Swiomentioning

confidence: 99%

“…It focuses on the meteorological and oceanic impact of TCs on the SWIO countries in the present and in the future. The four components of RNR-CYC and the observations implemented during this program are presented in the companion paper [15]. The objective of this paper is to present the modeling strategy of RNR-CYC in terms of forecasting and climate projection.…”

Section: Introductionmentioning

confidence: 99%

Impact of Tropical Cyclones on Inhabited Areas of the SWIO Basin at Present and Future Horizons. Part 2: Modeling Component of the Research Program RENOVRISK-CYCLONE

et al. 2021

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The ReNovRisk-Cyclone program aimed at developing an observation network in the south-west Indian ocean (SWIO) in close synergy with the implementation of numerical tools to model and analyze the impacts of tropical cyclones (TC) in the present and in a context of climate change. This paper addresses the modeling part of the program. First, a unique coupled system to simulate TCs in the SWIO is developed. The ocean–wave–atmosphere coupling is considered along with a coherent coupling between sea surface state, wind field, aerosol, microphysics, and radiation. This coupled system is illustrated through several simulations of TCs: the impact of air–sea flux parameterizations on the evolution of TC Fantala is examined, the full coupling developed during the program is illustrated on TC Idai, and the potential of novel observations like space-borne synthetic aperture radar and sea turtles to validate the atmosphere and ocean models is presented with TC Herold. Secondly, the evolution of cyclonic activity in the SWIO during the second half of the 21st century is assessed. It was addressed both using climate simulation and through the implementation of a pseudo global warming method in the high-resolution coupled modeling platform. Our results suggest that the Mascarene Archipelago should experience an increase of TC related hazards in the medium term.

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Impact of Tropical Cyclones on Inhabited Areas of the SWIO Basin at Present and Future Horizons. Part 1: Overview and Observing Component of the Research Project RENOVRISK-CYCLONE

Cited by 16 publications

References 119 publications

The Effect of Atmosphere-Ocean Coupling on the Structure and Intensity of Tropical Cyclone Bejisa in the Southwest Indian Ocean

The Effect of Atmosphere-Ocean Coupling on the Structure and Intensity of Tropical Cyclone Bejisa in the Southwest Indian Ocean

Cloud Radar Observations of Diurnal and Seasonal Cloudiness over Reunion Island

Impact of Tropical Cyclones on Inhabited Areas of the SWIO Basin at Present and Future Horizons. Part 2: Modeling Component of the Research Program RENOVRISK-CYCLONE

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