ORCID Profile
0000-0001-8056-8875
Current Organisation
Monash University
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Publisher: MDPI AG
Date: 10-2020
DOI: 10.3390/JMSE8100773
Abstract: Numerous studies have identified the complexities of the wave climatology around the South African coast, but limited studies have investigated these complex dynamics in the available literature. Several freely available parameterized wave boundary conditions are produced around southern Africa. However, none of these are fully spectral outputs from global or larger regional spectral wave models. This constraint results in local engineering and scientific organizations, reconstructing their own spectral boundary conditions. For coastal models, this is a reasonable assumption, assuming that the single parameterization is accurate and a representation of a non-multimodal sea state. The South African Weather Service (SAWS) Marine unit recently launched their coupled, operational wave and storm surge forecasting model. The aim of the SAWS Wave and Storm Surge (SWaSS) platform was to provide accurate, high-resolution coastal forecasts for the entire South African coastline. The present investigation thus presents the validation of the spectral wave component of the coupled system, developed in Delft3D. Various wave boundary reconstructions are investigated together with the two most used and well-known whitecapping formulations. Validation is performed with both in situ wave-rider buoy data (at nine locations along the coastline) and regional remotely sensed, along track, altimetry data. Full model performance statistics are provided, and the accuracy of the model is discussed.
Publisher: Elsevier BV
Date: 02-2021
Publisher: Informa UK Limited
Date: 08-02-2021
Publisher: American Geophysical Union (AGU)
Date: 07-2020
DOI: 10.1029/2020JC016321
Publisher: Springer Science and Business Media LLC
Date: 17-08-2020
Publisher: MDPI AG
Date: 28-11-2022
Abstract: Warnings of severe weather with a lead time longer that two hours require the use of skillful numerical weather prediction (NWP) models. In this study, we test the performance of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Conformal Cubic Atmospheric Model (CCAM) in simulating six high-impact weather events, with a focus on rainfall predictions in South Africa. The selected events are tropical cyclone Dineo (16 February 2017), the Cape storm (7 June 2017), the 2017 Kwa-Zulu Natal (KZN) floods (10 October 2017), the 2019 KZN floods (22 April 2019), the 2019 KZN tornadoes (12 November 2019) and the 2020 Johannesburg floods (5 October 2020). Three configurations of CCAM were compared: a 9 km grid length (MN9km) over southern Africa nudged within the Global Forecast System (GFS) simulations, and a 3 km grid length over South Africa (MN3km) nudged within the 9 km CCAM simulations. The last configuration is CCAM running with a grid length of 3 km over South Africa, which is nudged within the GFS (SN3km). The GFS is available with a grid length of 0.25°, and therefore, the configurations allow us to test if there is benefit in the intermediate nudging at 9 km as well as the effects of resolution on rainfall simulations. The South African Weather Service (SAWS) station rainfall dataset is used for verification purposes. All three configurations of CCAM are generally able to capture the spatial pattern of rainfall associated with each of the events. However, the maximum rainfall associated with two of the heaviest rainfall events is underestimated by CCAM with more than 100 mm. CCAM simulations also have some shortcomings with capturing the location of heavy rainfall inland and along the northeast coast of the country. Similar shortcomings were found with other NWP models used in southern Africa for operational forecasting purposes by previous studies. CCAM generally simulates a larger rainfall area than observed, resulting in more stations reporting rainfall. Regarding the different configurations, they are more similar to one another than observations, however, with some suggestion that MN3km outperforms other configurations, in particular with capturing the most extreme events. The performance of CCAM in the convective scales is encouraging, and further studies will be conducted to identify areas of possible improvement.
Publisher: Wiley
Date: 07-2023
DOI: 10.1002/QJ.4503
Abstract: Heavy rainfall occurs frequently on the subtropical eastern seaboard of Australia (ESB). Many rainfall events are associated with slow‐moving, upper‐level low‐pressure systems. Combined with moisture‐rich easterly winds associated with a surface anticyclone, these systems can produce heavy rainfall, leading to flooding events. Although the general meteorology of these events has been documented, much of the focus has been on surface processes, with limited attention paid previously to the dynamics aloft. Here, we investigate the upper‐level dynamics associated with heavy rainfall events over the ESB with the use of a coherent potential vorticity (PV) minimum climatology on the 330‐K isentropic level. Slow‐moving coherent cyclonic PV anomalies produce more rainfall than fast‐moving anomalies over the ESB. Rossby‐wave breaking is responsible for the development of a slow‐moving coherent cyclonic PV anomaly as well as the commonly observed surface patterns that are necessary for heavy rainfall over the ESB. Slow cyclonic coherent PV anomalies are either transported equatorwards into the Tropics, where they may influence tropical weather systems, or removed from the region by the restoration of the subtropical jet over continental Australia.
Publisher: Copernicus GmbH
Date: 09-11-2022
Abstract: Abstract. Stratospheric intrusions of high potential vorticity (PV) air are well-known drivers of cyclonic development throughout the troposphere. PV anomalies have been well studied with respect to their effect on surface cyclogenesis. A gap however exists in the scientific literature describing the effect that stratospheric intrusion depth has on surface cyclogenetic forcing. Numerical experiments using PV inversion diagnostics reveal that stratospheric depth is crucial in the intensity of cyclonic circulation induced at the surface. In an idealized setting, shallow, high-PV intrusions (above 300 hPa) resulted in a marginal effect on the surface, whilst growing stratospheric depth resulted in enhanced surface pressure anomalies and surface cyclonic circulation. It is shown that the height above the surface that intrusions reach is more critical than the vertical size of the intrusion when inducing cyclonic flow at the surface. This factor is however constrained by the height of the dynamical tropopause above the surface. The width of the stratospheric intrusion is an additional factor, with broader intrusions resulting in enhanced surface cyclogenetic forcing.
Publisher: Springer Science and Business Media LLC
Date: 09-02-2021
Publisher: Elsevier BV
Date: 08-2019
Publisher: Springer Science and Business Media LLC
Date: 14-05-2020
No related grants have been discovered for Michael Barnes.