ORCID Profile
0000-0003-0672-1012
Current Organisations
Monash University
,
CSIRO
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Publisher: American Meteorological Society
Date: 15-11-2016
Abstract: The 5-day Rossby–Haurwitz wave is unlike other large-scale wave modes that interact with tropical rainfall in that associated rainfall presents as a modulation of localized areas of rainfall instead of propagating with the wave. This form of wave-modulated convective organization in climate models has received little attention. This study investigates the simulation of interactions between the 5-day wave and tropical convection in 30 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and compares these with the interaction diagnosed from ERA-Interim and TRMM precipitation data. Models simulate the dry dynamics of the 5-day wave well, with realistic coherences between upper- and lower-tropospheric winds, as well as magnitudes and geographic distribution of wave wind anomalies being close to observations. The models consistently display significant coherences between 5-day-wave zonal winds and precipitation but perform less well at simulating the spatial distribution and magnitude of precipitation anomalies. For ex le, a third of the models do not reproduce significant observed anomalies near the Andes, and the best-performing model simulates only 38% of the observed variance over the tropical Andes and 24% of the observed variance over the Gulf of Guinea. Models with higher resolution perform better in simulating the magnitude of the Andean rainfall anomalies, but there is no similar relationship over the Gulf of Guinea. The evidence therefore suggests that the simulated interaction is mostly one way only, with the wave dynamics forcing the precipitation variations on the 5-day time scale.
Publisher: The Optical Society
Date: 29-03-2013
DOI: 10.1364/OL.38.001137
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: American Meteorological Society
Date: 02-2020
Abstract: Convection over the western equatorial Indian Ocean (WEIO) is strongly linked to precipitation over Africa and Australia but is poorly represented in current climate models, and its observed seasonal cycle is poorly understood. This study investigates the seasonal cycle of convection in the WEIO through rainfall and cloud measurements. Rainfall shows a single annual peak in early austral summer, but cloud proxies identify convective activity maxima in both boreal and austral summer. These erging measures of convection during boreal summer are indicative of a reduction in the intensity of precipitation associated with a given cloud regime or cloud-top height during this time of year but an increase in the overall occurrence of high-top clouds and convectively active cloud regimes. The change in precipitation intensity associated with regimes is found to explain most of the changes in total precipitation during the period from May to November, whereas changes in the occurrence of convective regimes explains most of the changes throughout the rest of the year. The reduction in precipitation intensities associated with cloud regimes over the WEIO during boreal summer appears to be related to large-scale monsoon circulations, which suppress convection through forcing air descent in the midtroposphere and increase the apparent occurrence of convectively active cloud regimes through the advection of high-level cloud from monsoon-active areas toward the WEIO region.
Publisher: American Geophysical Union (AGU)
Date: 02-09-2020
DOI: 10.1029/2020JD033223
Publisher: American Meteorological Society
Date: 11-2017
Abstract: Reanalysis data and satellite-derived rainfall measurements are examined to determine possible mechanisms linking the “5 day” Rossby–Haurwitz wave to localized variations of tropical convection. The mechanisms in all regions rely on the modulation of zonal winds near the equator by the wave, but the nature of these mechanisms depends strongly on local topography and local climate. In the upper Amazon basin, the wave modulates the strength of prevailing easterlies and thus the upslope flow and associated convection on the eastern edge of the Andes. Similar modulation of upslope flow is involved off the Panamanian and Colombian Pacific coasts, but the deflection and confluence of low-level wind in the presence of the Andes and moisture transports across the Andes from the Amazon basin are also factors. Similar deflection and confluence of winds around and through the Maritime Continent lead to low-level ergence and convection anomalies over the eastern Indian Ocean. Anomalous moisture transports from the Congo basin to the eastern and northeastern Gulf of Guinea due to the wave affect atmospheric moisture over the Gulf of Guinea and thus convection in the region. Over oceanic convergence zones, modulations of the prevailing winds by the wave affect the overall wind magnitude, changing evaporation from the ocean surface and atmospheric moisture. Most of these mechanisms arise from the nonuniform nature of Earth’s surface and suggest that other external Rossby–Haurwitz waves may have similar interactions with convection.
Publisher: Wiley
Date: 12-01-2021
DOI: 10.1002/JOC.6984
Publisher: American Association for the Advancement of Science (AAAS)
Date: 03-08-2020
Abstract: Millennia-long climate model simulations suggest that the 2005 North Atlantic hurricane season produced close to the maximum number of tropical cyclones that this basin can sustain in a given year under current climate conditions.
Publisher: American Meteorological Society
Date: 09-2015
Abstract: The seasonality, regionality, and nature of the association between tropical convection and the 5-day wavenumber-1 Rossby–Haurwitz wave are examined. Spectral coherences between daily outgoing longwave radiation (OLR), a proxy for convection, and 850-hPa zonal wind over the period January 1979–February 2013 are compared for different seasons and for phases of El Niño–Southern Oscillation (ENSO) and the quasi-biennial oscillation (QBO). Increased coherence, indicating a stronger association, occurs in boreal spring and autumn, with slightly reduced coherence in boreal summer and significantly reduced coherence in boreal winter. The regionality of the association is examined using lagged-regression techniques. Significant local signals in tropical convection are found over West Africa, the tropical Andes, the eastern Pacific Ocean, and the Marshall Islands. The relative phasing between the 5-day wave wind and OLR signals is in quadrature in Africa and the Marshall Islands, in phase with easterlies over the Andes, and out of phase with easterlies over the eastern Pacific. Frequency spectra of precipitation averaged over the identified local regions reveal spectral peaks in the 4–6-day range. The phasing between the large-scale wind and local convection signals suggests that the 5-day wave is actively modulating the convection around the Americas.
Location: Australia
No related grants have been discovered for Malcolm King.