The role of tropical-extratropical interaction and synoptic variability in maintaining the South Pacific Convergence Zone in CMIP5 models

The South Pacific Convergence Zone (SPCZ) is simulated as too zonal a feature in current generation climate models, including those in Phase 5 of the Coupled Model Intercomparison Project (CMIP5). This zonal bias induces errors in tropical convective heating, with subsequent effects on global circulation. The SPCZ structure, particularly in the subtropics, is governed by the tropical-extratropical interaction between transient synoptic systems and the mean background state. However, the fidelity of synoptic-scale interactions as simulated by CMIP5 models has not yet been evaluated. In this study, analysis of synoptic variability in the simulated subtropical SPCZ reveals that the basic mechanism of tropical-extratropical interaction is generally well simulated, with storms approaching the SPCZ along comparable trajectories to observations. However, there is a broad spread in mean precipitation and its variability across the CMIP5 ensemble. Inter-model spread appears to relate to a biased background state in which the synoptic waves propagate. In particular, the region of mean negative zonal stretching deformation or "storm graveyard" in the upper troposphere?a feature previously determined to play a key role in SPCZ-storm interactions?is typically displaced in CMIP5 models to the northeast of its position in reanalysis data, albeit with individual model graveyards displaying a pronounced (25 degree) longitudinal spread. From these findings, we suggest that SPCZs simulated by CMIP5 models are not simply too zonal; rather, in models the subtropical SPCZ manifests a diagonal tilt similar to observations while SST biases force an overly zonal tropical SPCZ, resulting in a more disjointed SPCZ than observed

CSIRO Marine and Atmospheric Research, 2

With over 84 % of Australians living in urban areas (populations over 30,000), the outcome of the current debate on water use in cities and how to match water demand to supply under both current and future climates, has the potential to affect many Australians. Lacking in this debate is a sound quantitative basis for assessing the environmental and economic benefits of water use in urban areas. As an example, while water sensitive urban design (WSUD) is widely accepted as a tool to manage the impacts of urbanisation by careful design at the house and street scale, its focus has largely been on managing and re-using the runoff (stormwater and wastewater) component of the water balance. Much less attention has been paid to the role of urban evapotranspiration (ET) by urban hydrologists, even though this it is often the biggest output in the water balance. Evapotranspiration is the process that links the movement of water through a landscape with the local climate, with the process using energy that would otherwise contribute to elevated air temperatures. This passive control of the local climate via urban vegetation and ET has a direct influence on quantities of energy used in space heating and cooling through the role of urban ET and also because trees provide shade and shelter. This link between the urban water and energy balances, and microclimate, is demonstrated by considering the following simplified expressions for i) the urban water balance: P+ I = ET + D+ΔS (1) where the inputs are: P = precipitation; I = piped water supply (for external and internal uses); and the outputs are: ET = urban evapotranspiration; D = stormwater and wastewater; ΔS = change in stored water on and within the surface materials; and ii) the urban energy balance: Q + QF = QH + QE +ΔQ

Modelling Sub-daily Latent Heat Fluxes from a Small Reservoir

Abstract Accurate methods of latent heat flux quantification are essential for water management and for use in hydrological and meteorological models. Currently the effect of small lakes in most numerical weather prediction modelling systems is either entirely ignored or crudely parameterized. In order to test methods for modelling hourly latent heat flux from small water bodies, this study compares results from several modelling approaches to values measured by the eddy covariance method at an agricultural reservoir in southeast Queensland, Australia. Mass transfer estimates of LE calculated using the theoretical mass transfer model and using the Tanny et al

the 1999 SPE Annual Technical Con-ference and Exhibition

Abstract We have developed methods of conditioning non-stationary Levy-stable geostatistical models 1,2 to 3D seismic data. The technique involves adapting the sequential Levy simulation method such that the convolutional response of the realisations acceptably 'matches' the seismic amplitude map. A rejection scheme is used, which requires fast repetitive simulation of gridblock columns and generation of convolutional responses. The non-stationarity of the model means that this cannot be achieved using the conventional large kriging system. We use a different, but comparably rapid method, based on storing the relevant parts of a sequential simulation calculation for the column. Working directly with the amplitude traces also has the advantage of avoiding the ambiguities and non-uniqueness involved in inverting the traces to acoustic impedance. The most difficult part of the problem is estimation of the seismic wavelet, and this is often done non-optimally. We describe a sophisticated method of estimating the wavelet, and show that this can yield better than expected results. Suitable rejection criteria are proposed, based on reasonable probabilistic models. The application of the technique is demonstrated with a field example

Spatial Variation of Extreme Rainfall Observed From Two Century‐Long Datasets

This paper presents the spatial variation of area‐orientated annual maximum daily rainfall (AMDR), represented by well‐fitted generalized extreme value (GEV) distributions, over the last century in Great Britain (GB) and Australia (AU) with respect to three spatial properties: geographic locations, sizes, and shapes of the region‐of‐interest (ROI). The results show that the spatial variation of GEV location‐scale parameters is dominated by geographic locations and area sizes. In GB, there is an eastward‐decreasing banded pattern compared with a concentrically increasing pattern from the middle to coasts in AU. The parameters tend to decrease with increased area sizes in both studied regions. Although the impact of the ROI shapes is insignificant, the round‐shaped regions usually have higher‐valued parameters than the elongated ones. These findings provide a new perspective to understand the heterogeneity of extreme rainfall distribution over space driven by the complex interactions between climate, geographical features, and the practical sampling approaches

Revegetation guide to the central wheatbelt

The rapid development of the central wheatbelt for agriculture over the past century has produced a productive farming landscape, but one which is increasingly subject to degradation. Erosion, salinization, declining soil structure, waterlogging and acidification are all symptoms of this degradation and causes of lost agricultural production. In addition, most of the native vegetation and many of the native animals have disappeared, and the natural heritage of the area resides in small scattered patches that together make up only seven per cent of the wheatbelt region. Many farmers now recognize that replanting trees and shrubs is an effective means of reversing many of the current trends towards land degradation. However, advice on how to go about revegetation, where to plant and which species to use has been hard to obtain. This guide is an attempt to redress this by providing lists of local species grouped according to soil types. It also provides a summary of current knowledge of revegetation methods. It has been put together using information from many sources including farmers, foresters, botanists and ecologists. It has been developed as a direct result of a workshop organized by CSIRO Division.https://researchlibrary.agric.wa.gov.au/bulletins/1106/thumbnail.jp

Domain-based perceptions of risk:a case study of lay and technical community attitudes towards managed aquifer recharge

Despite growing water scarcity, communities in many parts of the developed world often reject technically and economically sound options for water augmentation. This paper reports findings from a study investigating risk perceptions associated with a proposed Managed Aquifer Recharge scheme in Australia. Q-Methodology was used to compare decision-making frameworks of lay community and „technical expert‟ participants. Technical expert participants were also asked to approximate the decision-making framework of a „typical‟ community member. The emerging contrasts between lay community frameworks and those approximated by technical experts suggest that there are prevailing yet errant assumptions about lay community attitudes towards new technologies. The findings challenge the characterisation of the lay community and technical experts as being in entrenched opposition with one another