ORCID Profile
0000-0002-2039-5025
Current Organisation
Australian Bureau of Meteorology
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Publisher: Wiley
Date: 2020
Publisher: American Geophysical Union (AGU)
Date: 05-2020
DOI: 10.1029/2019EF001469
Publisher: Wiley
Date: 07-02-2014
DOI: 10.1002/JOC.3916
Publisher: Wiley
Date: 2020
Publisher: American Geophysical Union (AGU)
Date: 04-2022
DOI: 10.1029/2021EF002625
Abstract: Global climate models (GCMs) are essential for investigating climate change, but their coarse scale limits their efficacy for climate adaptation planning at the regional scales where climate impacts manifest. Dynamical downscaling of GCM outputs better resolves regional climate and thus provides improved guidance for climate policy at regional scales. Being expensive to run, downscaling uses a subset of GCMs, necessitating careful GCM selection. This evaluation identifies a suitable subset of CMIP6 GCMs for downscaling over Australia by assessing in idual GCMs against three criteria: (a) performance simulating daily climate variable distributions, climate means, extremes, and modes (b) model independence and (c) climate change signal ersity. Over Australia, GCMs are generally biased cold (warm) for maximum (minimum) temperature, with larger biases for minimum temperature. GCMs are generally wet biased, especially over the monsoonal north, but dry biased over eastern regions. Most GCMs show larger biases for temperature and precipitation over geographically complex, heavily populated eastern regions, relative to other regions. Evaluations identify a distinct group of 11 GCMs that perform consistently poorly across climate variables, statistics, and timescales with widespread, statistically significant biases, versus 13 GCMs that show consistent adequate‐to‐good performance with substantially reduced errors. Assessment of model independence highlights the lack of independence between several high‐performing GCMs, particularly from allied modeling groups, demonstrating the importance of careful ensemble selection when making selective s les of climate space. Once GCM climate signal ersity is considered, 6–8 mid‐to‐high‐performing, independent GCMs occupy the full range of the future climate space and, thus, are suitable for dynamical downscaling over CORDEX‐Australasia.
Publisher: American Meteorological Society
Date: 10-12-2014
DOI: 10.1175/JCLI-D-14-00190.1
Abstract: Climate warming has large implications for rainfall patterns, and identifying the most plausible pattern of rainfall change over the next century among various model projections would be valuable for future planning. The spatial pattern of projected sea surface temperature change has a key influence on rainfall changes in the tropical Pacific Ocean. Here it is shown that simple indices of the size of the equatorial peak in the spatial pattern of warming and to a lesser extent the hemispheric asymmetry in warming are useful for classifying the surface temperature change in different models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). Models with a more pronounced equatorial warming show a fairly distinct rainfall response compared to those with more uniform warming, including a greater “warmer-get-wetter” or dynamical response, whereby rainfall increases follow the surface warming anomaly. Models with a more uniform warming pattern project a smaller rainfall increase at the equator and a rainfall increase in the southern tropical Pacific, a pattern that is distinct from the multimodel mean of CMIP5. Thus, the magnitude of enhanced equatorial warming and to some extent the hemispheric asymmetry in warming provides a useful framework for constraining rainfall projections. While there is not a simple emergent constraint for enhanced equatorial warming in models in terms of past trends or bias in the current climate, further understanding of the various feedbacks involved in these features could lead to a useful constraint of rainfall for the Pacific region.
Publisher: American Meteorological Society
Date: 07-2017
Abstract: The initiation of northern Australian monsoon rainfall bursts is accompanied by an increase in cyclonic circulation in the monsoon region. This study shows that the change in circulation at the start of the composite rainfall burst is predominantly influenced by midlatitude frontlike features. By exploiting the relationship between circulation tendency and the convergence of absolute vorticity flux, the circulation changes accompanying the initiation of Australian monsoon bursts is investigated. Moisture flux convergence is found to be proportional to the circulation changes in the monsoon region. Using a composite analysis it is shown that absolute vorticity fluxes through the southern boundary are by far the most important influence on monsoon burst circulation changes, with only one-third of events more closely related to other influences including the Madden–Julian oscillation. This is shown to be true throughout the wet season.
Publisher: American Geophysical Union (AGU)
Date: 22-08-2023
DOI: 10.1029/2023GL103913
Abstract: For over a century, numerous proposals for increasing available water in central Australia have been raised, inspired in part by the natural occurrence of the ephemeral lake, Kati Thanda‐Lake Eyre. It has also been proposed that additional rainfall generated by the lake would spread beyond the lake itself, potentially opening up large tracts of uncultivated land to dryland agriculture. Here we use a climate model to examine how adding a permanent lake to Australia's arid center might influence local and regional precipitation. Locally, evaporative cooling from the lake increases low‐level ergence, suppressing precipitation. Regionally, additional moisture from the lake is spread thinly over the Australian continent, resulting in little change to total precipitation. Overall, our results do not support the assertion that maintaining a large inland lake like Kati Thanda‐Lake Eyre in central Australia would significantly increase precipitation, either locally or regionally.
Publisher: American Geophysical Union (AGU)
Date: 28-06-2020
DOI: 10.1029/2019GL086816
Publisher: Elsevier BV
Date: 06-2015
Publisher: American Meteorological Society
Date: 10-2018
Abstract: The simulation of northern Australian wet season rainfall bursts by coupled climate models is evaluated. In idual models produce vastly different amounts of precipitation over the north of Australia during the wet season, and this is found to be related to the number of bursts they produce. The seasonal cycle of bursts is found to be poor in most of the models evaluated. It is known that northern Australian wet season bursts are often associated with midlatitude Rossby wave packets and their surface signature as they are refracted toward the tropics. The relationship between midlatitude waves and the initiation of wet season bursts is simulated well by the models evaluated. Another well-documented influence on the initiation of northern Australian wet season bursts is the Madden–Julian oscillation (MJO). No model adequately simulated the tropical outgoing longwave radiation temporal–spatial patterns seen in the reanalysis-derived OLR. This result suggests that the connection between the MJO and the initiation of northern Australian wet season bursts in models is poor.
Publisher: American Geophysical Union (AGU)
Date: 05-08-2019
DOI: 10.1029/2019GL083964
Abstract: Accurately representing the properties and impact of tropical convection in climate models requires an understanding of the relationships between the state of a convective cloud ensemble and the environment it is embedded in. We investigate this relationship using 13 years of radar observations in the tropics. Specifically, we focus on convective cell number and size and quantify their relationship to atmospheric stability, midtropospheric vertical motion and humidity. We find several key convective states embedded in their own unique environments. The most area‐averaged rainfall occurs with a moderate number of moderate size convective cell in an environment of high humidity, strong vertical ascent, and moderate convective available potential energy (CAPE) and convective inhibition (CIN). The strongest rainfall intensities are found with few large cells. Those exist in a dry and subsiding environment with both high CAPE and CIN. Large numbers of convective cells are associated with small CAPE and CIN, weak ascent, and a moist midtroposphere.
No related grants have been discovered for Sugata Narsey.