The growing season

IN AUSTRALIA the seasons of summer, autumn, winter and spring do not have the importance that they have in the Old World, and though summer and winter weather are quite different, there is not the obvious difference in autumn and spring conditions that there is in the colder countries. This is largely due to the difference in vegetation and in its life cycle in the different places

The impact of climate change and urban growth on urban climate and heat stress in a subtropical city

Urban residents face increasing risk of heat stress due to the combined impact of climate change and intensification of the urban heat island (UHI) associated with urban growth. Considering the combined effect of urban growth and climate change is vital to understanding how temperatures in urban areas will change in the future. This study investigated the impact of urban growth and climate change on the UHI and heat stress in a subtropical city (Brisbane, Australia) in the present day (1991–2000) and medium term (2041–2050; RCP8.5) during summer. A control and urban growth scenario was used to compare the temperature increase from climate change alone with the temperature increase from climate change and urban growth. Average and minimum temperatures increased more with climate change and urban growth combined than with climate change alone, indicating that if urban growth is ignored, future urban temperatures could be underestimated. Under climate change alone, rural temperatures increased more than urban temperatures, decreasing the effect of the UHI by 0.4 °C at night and increasing the urban cool island by 0.8 °C during the day. With climate change, the number of hot days and nights doubled in urban and rural areas in 2041–2050 as compared to 1991–2000. The number of hot nights was higher in urban areas and with urban growth. Dangerous heat stress, defined as apparent temperature above 40 °C, increased with climate change and occurred on average 1–2 days every summer during 2041–2050, even in shaded conditions. There was higher temperature increases with urban growth and climate change than with climate change alone, indicating that reducing the effect of the UHI is vital to ensuring urban growth does not increase the heat stress risks that urban residents will face in the future

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

A machine learning assisted development of a model for the populations of convective and stratiform clouds

Traditional parameterizations of the interaction between convection and the environment have relied on an assumption that the slowly-varying large-scale environment is in statistical equilibrium with a large number of small and short-lived convective clouds. They fail to capture non-equilibrium transitions such as the diurnal cycle and theformation of meso-scale convective systems as well asobserved precipitation statisticsand extremes. Informed by analysis of radar observations, cloud-permitting model simulation, theory and machine learning, this work presents a new stochastic cloud population dynamics model for characterizing the interactions between convective and stratiform clouds,with the ultimate goal of informing the representation ofthese interactions in global climate models. 15 wet seasons of precipitating cloud observations by a C-band radar at Darwin, Australia are fed into a machine learning algorithm to obtain transition functions that close a set of coupled equation relating large-scale forcing, mass flux, the convective cell size distribution and the stratiform area. Under realistic large-scale forcing, the derived transition functions show that, on the one hand, interactions with stratiform clouds act to dampen the variability in the size and number of convective cells and therefore in the convective mass flux. On the other hand, for a given convective area fraction, a larger number of smaller cells is more favorable for the growth of stratiform area than a smaller number of larger cells. The combination of these two factors gives rise to solutions with a number of convective cells embedded in a large stratiform area, reminiscent of mesoscale convective systems

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

Μελέτη επί της τρισδιάστατης απεικόνισης και αυτόματης ανακατασκευής τρισδιάστατων προϊστορικών αγγείων

88 σ.Στην παρούσα διπλωματική εργασία γίνεται, αρχικά, μία αναφορά σε αρχές της θεωρίας των καμπυλών και επιφανειών της διαφορικής γεωμετρίας οι οποίες αποτελούν ένα απαραίτητο μαθηματικό υπόβαθρό της σχετικής προσέγγισης. Δίνεται έμφαση σε βασικές έννοιες, όπως της καμπύλης, της επιφάνειας αλλά και άλλων μεγεθών-εργαλείων που τις συνοδεύουν, ούτως ώστε να γίνει εφικτή η προσέγγιση στο θέμα της αυτόματης ανασυγκρότησης θραυσμάτων. Στην συνέχεια, ακολουθεί περιγραφή της επεξεργασίας, την οποία υπέστησαν τρισδιάστατες απεικονίσεις θραυσμάτων αγγείων, οι οποίες προέρχονται από την τρισδιάστατη σάρωση των πραγματικών θραυσμάτων με τρισδιάστατο σαρωτή. Η παραπάνω επεξεργασία αποτελεί προκαταρκτικό στάδιο για την εφαρμογή μίας νέας μεθόδου η οποία προσφέρει αποτελεσματική λύση στο πρόβλημα της αυτόματης εικονικής ανασυγκρότησης των θραυσμένων αγγείων για την οποία γίνεται αναφορά στη συνέχεια.In this thesis, initially, a report on principles of the theory of curves and surfaces, in differential geometry, takes place. These principles are the mathematical background of this thesis. The understanding of basic concepts such as curve , surface and other sizes–tools which surround them, is emphasized thanks to which the approach to automatic reconstruction of fragments is feasible. Then, follows a description of the processing that was applied in three-dimensional representations of broken vessels. These represantations derived from the three-dimensional scan of the real fragments with three-dimensional scanner. The above process is a preliminary step for the implementation of a new method which is an effective solution to the problem of automatic virtual reconstruction of broken vessels to which reference is made below.Ιωάννης Γ. Κοτζά

The indirect response of an aquatic ecosystem to long-term climate-driven terrestrial vegetation in a subalpine temperate lake

Aim: To assess whether climate directly influences aquatic ecosystem dynamics in the temperate landscape of Tasmania or whether the effects of long-term climatic change are mediated through the terrestrial environment (indirect climate influence). Location: Paddy’s Lake is located at 1065 m a.s.l. in temperate north-west Tasmania, a continental island south-east of mainland Australia (41°15–43°250 S; 145°00– 148°150 E). Methods: We developed a new 13,400 year (13.4 kyr) palaeoecological dataset of lake sediment subfossil cladocerans (aquatic grazers), bulk organic sediment carbon (C%) and nitrogen (N%) and d13C and d15N stable isotopes. Comparison of this new data was made with a recently published pollen, geochemistry and charcoal records from Paddy’s Lake. Results: Low cladoceran diversity at Paddy’s Lake is consistent with other temperate Southern Hemisphere lakes. The bulk sediment d15N values demonstrate a significant lagged negative response to pollen accumulation rate (pollen AR). Compositional shifts of dominant cladoceran taxa (Bosmina meridionalis and Alona guttata) occur following changes in both pollen AR and pollen (vegetation) composition throughout the 13.4 kyr record at Paddy’s Lake. The d15N values demonstrate a significant positive lagged relationship to the oligotrophic:eutrophic cladoceran ratio. Main conclusions: Long-term changes in cladoceran composition lag changes in both pollen AR and terrestrial vegetation composition. We interpret pollen AR as reflecting climate-driven changes in terrestrial vegetation productivity and conclude that climate-driven shifts in vegetation are the principal driver of the cladoceran community during the last ca. 13.4 kyr. The significant negative lagged relationship between pollen AR and d15N reflects the primary control of vegetation productivity over within-lake nutrient status. Thus, we conclude that the effects of long-term climate change on aquatic ecosystem dynamics at our site are indirect and mediated by the terrestrial environment. Vegetation productivity controls organic soil development and has a direct influence over lake trophic status via changes in the delivery of terrestrial organic matter into the lake

Interaction of ENSO-driven Flood Variability and Anthropogenic Changes in Driving Channel Evolution: Corryong/ Nariel Creek, Australia

This is an Accepted Manuscript of an article published by Taylor & Francis in Australian Geographer on 03/09/2015, available online: 10.1080/00049182.2015.1048595Understanding the relative contributions of climatic and anthropogenic drivers of channel change are important to inform river management, especially in the context of environmental change. This global debate is especially pertinent in Australia as catchments have been severely altered since recent European settlement, and there is also strong evidence of cyclical climate variability controlling environmental systems. Corryong/Nariel Creek is an ideal setting to further study the interaction between climate and anthropogenic changes on channel evolution as it has experienced both significant periods of flood and drought, controlled by the El Niño Southern Oscillation (ENSO), and extensive anthropogenic changes. Since European settlement the floodplain has been completely cleared, the riparian zone almost entirely invaded by willows, and every reach of the channel has experienced some form of direct channel modification. Through the combined analysis of channel evolution, climate changes and anthropogenic history of the river it was found that both the ENSO-driven climate and anthropogenic drivers are significant, although at different scales of channel change. Significant straightening in response to land clearing in the early twentieth century occurred before any records of direct channel modifications. Following this, most river management works were in response to instabilities created in the clearing period, or to instabilities created by flooding triggering a new phase of instability in reaches which had already undergone stabilisation works. Overall, human activities triggered channel instability via land clearing, and management works since then generally exacerbated erosion during high flows that are driven by climate fluctuations. This research raises the interesting question of whether rivers in Australia have become more responsive to the ENSO cycle since the clearing of catchment and riparian vegetation, or whether the past response to climate variability was different