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Abstract Ultrafine particles (UFP) acting as cloud condensation nuclei (CCN) are the driving force behind changing rainfall patterns. Recently observed weather extremes like floods and drought might be due to changing anthropogenic UFP emissions. However, the sources and budgets of anthropogenic primary and secondary particles are not well known. Based on airborne measurements we identified as a major contribution modern fossil fuel flue gas cleaning techniques to cause a doubling of global primary UFP number emissions. The subsequent enhancement of CCN numbers has several side effects. It’s changing the size of the cloud droplets and delays raindrop formation, suppressing certain types of rainfall and increasing the residence time of water vapour in the atmosphere. This additional latent energy reservoir is directly available for invigoration of rainfall extremes. Additionally it’s a further contribution to the column density of water vapour as a greenhouse gas and important for the infrared radiation budget. The localized but ubiquitous fossil fuel related UFP emissions and their role in the hydrological cycle, may thus contribute to regional or continental climate trends, such as increasing drought and flooding, observed within recent decades.

[This corrects the article DOI: 10.1371/journal.pone.0233912.].

The Dampier Archipelago (Murujuga) is on Australia’s National Heritage List because of its significant rock art and numerous stone structures. When people first started living in this arid landscape of the north-west coast, 50,000 years ago, the shoreline was 160 kilometres further north-and west. The Archipelago was created around 7,000 years ago, with sea-level rise following the termination of the Last Glacial Maximum (LGM). Photogrammetry and microphotography (using LiDAR, RPA and Dino-Lite™) are used here to demonstrate how this combination of different scales of imaging can be used to better document the terrestrial Murujuga features record. This paper explores the utility of photogrammetry generated by LiDAR and RPA to locate and reconstruct two types of Aboriginal stone structure (standing stones and house structures) which are prevalent across the Archipelago. These combined techniques were deployed to better visualise and understand site distribution with a view to using the landscape scale methods for the detection of similar features in submerged contexts in the adjacent waters. It has been predicted that this more robust site type would be likely to survive being submerged by sea level rise, and hence this was a site type which we were interested in locating remotely. As well as undertaking systematic terrestrial survey and recording of sample areas across Rosemary Island, topographic LiDAR was flown on two occasions (2017, 2018). These flights were separated by a wildfire which burnt most of the spinifex cover across the island. It highlights the potential – and shortcomings – of remote sensing this type of cultural sites in a naturally rocky and spinifex-covered landscape. It makes recommendations about how to better implement LiDAR to assist in the understanding of the landscape context of these hunter-gatherer stone features.

This article reports Australia's first confirmed ancient underwater archaeological sites from the continental shelf, located off the Murujuga coastline in north-western Australia. Details on two underwater sites are reported: Cape Bruguieres, comprising > 260 recorded lithic artefacts at depths down to -2.4 m below sea level, and Flying Foam Passage where the find spot is associated with a submerged freshwater spring at -14 m. The sites were discovered through a purposeful research strategy designed to identify underwater targets, using an iterative process incorporating a variety of aerial and underwater remote sensing techniques and diver investigation within a predictive framework to map the submerged landscape within a depth range of 0-20 m. The condition and context of the lithic artefacts are analysed in order to unravel their depositional and taphonomic history and to corroborate their in situ position on a pre-inundation land surface, taking account of known geomorphological and climatic processes including cyclone activity that could have caused displacement and transportation from adjacent coasts. Geomorphological data and radiometric dates establish the chronological limits of the sites and demonstrate that they cannot be later than 7000 cal BP and 8500 cal BP respectively, based on the dates when they were finally submerged by sea-level rise. Comparison of underwater and onshore lithic assemblages shows differences that are consistent with this chronological interpretation. This article sets a foundation for the research strategies and technologies needed to identify archaeological targets at greater depth on the Australian continental shelf and elsewhere, building on the results presented. Emphasis is also placed on the need for legislation to better protect and manage underwater cultural heritage on the 2 million square kilometres of drowned landscapes that were once available for occupation in Australia, and where a major part of its human history must lie waiting to be discovered.

Reef islands are some of the most highly sensitive landforms to the impacts of future environmental change. Previous assessments of island morphodynamics primarily relied on historical aerial and satellite imagery. These approaches limit analysis to two-dimensional parameters, with no ability to assess long-term changes to island volume or elevation. Here, we use high-resolution airborne LiDAR data to assess three-dimensional reef island features for 22 islands along the north-western coast of Australia. Our primary objective was to utilize two regional LiDAR datasets to identify characteristics indicative of island sensitivity and future vulnerability. Results show reef platform area to be an accurate predictor of island area and volume suggesting larger island volumes may reflect (1) increased carbonate production and supply from the reef platform and/or (2) enhanced shoreline protection by larger reef platforms. Locations of foredune scarping (an erosional signature) and island orientations were aligned to the regional wind and wave climate. Reef island characteristics (island area, volume, elevation, scarping, and platform area) were used to rank islands according to sensitivity, using a new Island Sensitivity Characteristics Index (ISCi) where low ISCi indicates stable islands (large areas and volumes, high elevations, and fewer scarped areas) and high ISCi indicates unstable islands (small areas and volumes, low elevations, and more scarped areas). Comparison of two LiDAR surveys from 2016 and 2018 validates the use of 3D morphometrics as important (direct) measurements of island landform change, and can complement the use of 2D parameters (e.g., area) moving forward. Results demonstrate that ongoing use of airborne LiDAR and other 3D technology for monitoring coral reef islands at regional scales will enable more accurate quantification of their sensitivity to future impacts of global environmental change.

We demonstrate the efficacy of a commercial portable 2D laser scanner (operating at a wavelength close to 1,000 nm) deployed from a fixed-wing aircraft for measuring the sea surface topography and wave profiles over coastal waters. The LiDAR instrumentation enabled simultaneous measurements of the 2D laser scanner with two independent inertial navigation units, and also simultaneous measurements with a more advanced 2D laser scanner (operating at a wavelength near 1,500 nm). The latter scanner is used routinely for accurately measuring terrestrial topography and was used as a benchmark in this study. We present examples of sea surface topography and wave profiles based on low altitude surveys (< ~300 m) over coastal waters in the vicinity of Cape de Couedic, Kangaroo Island, South Australia and over the surf zone adjacent to the mouth of the Murray River, South Australia. Relative wave heights in the former survey are shown to be consistent with relative wave heights observed from a waverider buoy located near Cape de Couedic during the LiDAR survey. The sea surface topography of waves in the surf zone was successfully mapped with both laser scanners resolving relative wave height variations and fine structure of the sea surface to within approximately 10 cm. A topographic map of the sea surface referenced to the airborne sensor frame transforms to an accurate altimetry map which may be used with airborne electromagnetic instrumentation to provide an averaged altimetry covering a portion of the larger electromagnetic footprint. This averaged altimetry is deemed to be significantly more reliable as a measurement of altimetry than spot measurements using a nadir-looking laser altimeter and would therefore improve upon the use of airborne electromagnetic methods for bathymetric mapping in surf-zone waters. The aperture range of the scanner does not necessarily determine the swath. We observed that instead, the maximum swath at a given altitude was limited by the angle of incidence of the laser at the water surface.

It is critical to assess bushfire impact rapidly and accurately because bushfires play a significant role in forest degradation and present a threat to ecosystems and human lives. Over the past decades, several supervised algorithms of burn severity mapping have been proposed, facing the significant drawback of time-consuming labeling. Moreover, there is no robust framework for burn severity mapping through fusing multi-sensor, multi-resolution, and multi-temporal remote sensing imagery from satellite and aerial platforms. Therefore, this paper presents an unsupervised two-step pipeline: processing 2D data followed by 3D data for burn severity mapping, both of which are acquired from either aircraft or satellites. For the 2D data processing, our proposed unsupervised burned area detection (UsBA detection) model enhances burned area mapping accuracy by integrating Ultra-High Resolution (UHR) aerial imagery with bi-temporal medium-resolution PlanetScope imagery, using a Segment Anything Model (SAM)-assisted UNetFormer (pre-trained on the target-style public dataset – LoveDA Rural) for refinement. The model demonstrates superior burned area segmentation, evidenced by improved evaluation metrics calculated from labeled test sites. For the 3D analysis, the burned areas extracted from 2D processing are further assessed using pre- and post-event airborne laser data. We implement a voxel-based workflow, including necessary steps such as ground filtering through Superpoints in RANSAC Planes (SiRP) method and biomass change analysis. The results indicate that the 3D branch provides a reliable lower bound of the actual damage map, because the vegetation growth between two measurements remains, in essence, undetected. The proposed framework offers a more accurate and robust solution for burn severity mapping utilizing combined 2D and 3D data, evaluated on a multi-source dataset from a real bushfire event that occurred in Bushland Park, South Australia. [ABSTRACT FROM AUTHOR]

In 2019, the Deep History of Sea Country (DHSC) Project team found and published two submerged archaeological sites in Murujuga (Dampier Archipelago) Western Australia [[1]]. Please see the authors' respective ORCID iDs here: Author Jo McDonald's ORCID iD is 0000-0002-2701-7406 (https://orcid.org/0000-0002-2701-7406) Author Patrick Morrison's ORCID iD is 0000-0003-0920-3405 (https://orcid.org/0000-0003-0920-3405) Additionally, the contributions for author Patrick Morrison are updated as follows: Data curation, Formal analysis, Methodology, Investigation, Software, Visualization, Writing-original draft, Writing-review & editing. This supersedes the original data in the article, and it is not possible to identify which of the samples constituted the original dataset of 455 terrestrial artefacts. [Extracted from the article]

Point clouds acquired through laser scanning techniques are applied in the three-dimensional modelling of vegetation. They provide the three-dimensional coordinates of geometric surfaces with attributes. However, raw point clouds are unstructured and do not provide semantic, geometric, or topological information about an object. Voxelisation is a method for structuring point clouds. It is a generalisation of point clouds and therefore the voxel size and the voxel neighbourhood play a critical role in the processing. This research explores the influence of voxelisation of point clouds acquired of heathland in Australia and how it influences the three-dimensional modelling and the representation of important heathland structure using different voxel sizes and voxel connectivities. Voxel sizes of 0.4 m, 0.6 m, 1.0 m, 1.2 m and 1.6 m with a voxel neighbourhood connectivity of 6, 18 and 26 are examined for three-dimensional modelling and segmentation of heathland vegetation in Australia. The results indicate that the choice of voxel size and the voxel connectivity influence the representation of important heathland parameters. A smaller voxel size of 0.4 m provides a detailed representation of mallee structure while the the processing time is longer compared to a larger voxel size. While a larger voxel size produces blobs while the processing speed is shorter. The results from the voxel neighbourhood connectivity represent a stronger voxel connectivity of 26-connected voxels suitable for heathland modelling rather than a 6-connected voxels. [ABSTRACT FROM AUTHOR]

Ultrafine particles (UFP) acting as cloud condensation nuclei (CCN) are the driving force behind changing rainfall patterns. Recently observed weather extremes like floods and drought might be due to changing anthropogenic UFP emissions. However, the sources and budgets of anthropogenic primary and secondary particles are not well known. Based on airborne measurements we identified as a major contribution modern fossil fuel flue gas cleaning techniques to cause a doubling of global primary UFP number emissions. The subsequent enhancement of CCN numbers has several side effects. It's changing the size of the cloud droplets and delays raindrop formation, suppressing certain types of rainfall and increasing the residence time of water vapour in the atmosphere. This additional latent energy reservoir is directly available for invigoration of rainfall extremes. Additionally it's a further contribution to the column density of water vapour as a greenhouse gas and important for the infrared radiation budget. The localized but ubiquitous fossil fuel related UFP emissions and their role in the hydrological cycle, may thus contribute to regional or continental climate trends, such as increasing drought and flooding, observed within recent decades. [ABSTRACT FROM AUTHOR]

Bushfires are an intrinsic part of the New South Wales' (NSW) environment in Australia, especially in the Blue Mountains region (11400km2), that is dominated by fire prone vegetation that includes heathland. Many of the Australian native plants in this region are fire-prone and combustible, and many species even require fire to regenerate. The classification of the lateral and vertical distribution of living vegetation is necessary to manage the complexity of bushfires. Currently, interpretation of aerial and satellite images is the prevalent method for the classification of vegetation in NSW. The result does not represent important vegetation structural attributes, such as vegetation height, subcanopy height, and destiny. This paper presents an automated method for the three-dimensional modelling of heathland and important heathland parameters, such as heath shrub height and continuity, and sparse tree and mallee height and density in support of bushfire behaviour modelling. For this study airborne lidar point clouds with a density of 120 points per square meter are used. For the processing and modelling the study is divided into a point cloud processing phase and a voxel-based modelling phase. The point cloud processing phase consists of the normalisation of the height and extraction of the above ground vegetation, while the voxel phase consists of seeded region growing for segmentation, and K-means clustering for the classification of the vegetation into three different canopy layers: a) heath shrubs, b) sparse trees and mallee, c) tall trees. [ABSTRACT FROM AUTHOR]

In regions where there are multiple sources of methane (CH4) in close proximity, it can be difficult to apportion the CH4 measured in the atmosphere to the appropriate sources. In the Surat Basin, Queensland, Australia, coal seam gas (CSG) developments are surrounded by cattle feedlots, grazing cattle, piggeries, coal mines, urban centres and natural sources of CH4. The characterization of carbon (δ13C) and hydrogen (δD) stable isotopic composition of CH4 can help distinguish between specific emitters of CH4. However, in Australia there is a paucity of data on the various isotopic signatures of the different source types. This research examines whether dual isotopic signatures of CH4 can be used to distinguish between sources of CH4 in the Surat Basin. We also highlight the benefits of sampling at nighttime. During two campaigns in 2018 and 2019, a mobile CH4 monitoring system was used to detect CH4 plumes. Sixteen plumes immediately downwind from known CH4 sources (or individual facilities) were sampled and analysed for their CH4 mole fraction and δ13CCH4 and δDCH4 signatures. The isotopic signatures of the CH4 sources were determined using the Keeling plot method. These new source signatures were then compared to values documented in reports and peer-reviewed journal articles. In the Surat Basin, CSG sources have δ13CCH4 signatures between -55.6 ‰ and -50.9 ‰ and δDCH4 signatures between -207.1 ‰ and -193.8 ‰. Emissions from an open-cut coal mine have δ13CCH4 and δDCH4 signatures of -60.0±0.6 ‰ and -209.7±1.8 ‰ respectively. Emissions from two ground seeps (abandoned coal exploration wells) have δ13CCH4 signatures of -59.9±0.3 ‰ and -60.5±0.2 ‰ and δDCH4 signatures of -185.0±3.1 ‰ and -190.2±1.4 ‰. A river seep had a δ13CCH4 signature of -61.2±1.4 ‰ and a δDCH4 signature of -225.1±2.9 ‰. Three dominant agricultural sources were analysed. The δ13CCH4 and δDCH4 signatures of a cattle feedlot are -62.9±1.3 ‰ and -310.5±4.6 ‰ respectively, grazing (pasture) cattle have δ13CCH4 and δDCH4 signatures of -59.7±1.0 ‰ and -290.5±3.1 ‰ respectively, and a piggery sampled had δ13CCH4 and δDCH4 signatures of -47.6±0.2 ‰ and -300.1±2.6 ‰ respectively, which reflects emissions from animal waste. An export abattoir (meat works and processing) had δ13CCH4 and δDCH4 signatures of -44.5±0.2 ‰ and -314.6±1.8 ‰ respectively. A plume from a wastewater treatment plant had δ13CCH4 and δDCH4 signatures of -47.6±0.2 ‰ and -177.3±2.3 ‰ respectively. In the Surat Basin, source attribution is possible when both δ13CCH4 and δDCH4 are measured for the key categories of CSG, cattle, waste from feedlots and piggeries, and water treatment plants. Under most field situations using δ13CCH4 alone will not enable clear source attribution. It is common in the Surat Basin for CSG and feedlot facilities to be co-located. Measurement of both δ13CCH4 and δDCH4 will assist in source apportionment where the plumes from two such sources are mixed. [ABSTRACT FROM AUTHOR]

Here, we utilise a unique, 70-year-long (1949–2017), high-resolution historical aerial imagery dataset to track changes to coral reef structures in Bill's Bay on the Ningaloo coast. Reef habitat was distinguished from sand and rubble substrates based on imagery greyscale values and autoclassified using unsupervised image analysis in ArcMap. This approach was validated through comparison of reef structure (defined by bathymetric LiDAR imagery), greyscale values of aerial photography taken during the same survey, and in-water ground-truthed photographs. Long-term (1990–2015) live coral cover data were then compared with changes in reef structure. Reef structure increased from 11 to 38% within Bill's Bay between 1949 and 1990. A coral spawn-induced hypoxia event in 1989 caused a loss of live coral cover from 50 to 7%, a 25% reduction in reef structure by 2002, and a switch from branching to massive coral-dominated reef. From 2002, reef structure recovered and continued to expand, peaking at 41% of total area (2017). Live coral cover in 2015 (46%) matches this measured increase in reef structure, despite a drop in coral cover in 2008. Discrepancies observed between live coral cover and reef structure during the 2002–2010 period reflect the persistence of the massive dominated coral community and in situ dead reef framework. Across the entire study period, reef growth was most prominent along the south-western edge of the bay, possibly due to an increase in the availability of hard substrate for coral recruitment. This study provides new insights into reef health over decadal timescales by capturing changes in reef geomorphology that go beyond the spatial scale and scope of traditional in-water assessments. These data further highlight that coral reef structure in Bill's Bay has expanded even with frequent natural disturbances affecting the region over the last 70 years. [ABSTRACT FROM AUTHOR]

A carbonate budget is a comprehensive measure of reef health and function that focuses on processes that produce and remove carbonate. A key parameter of a carbonate budget is reef topographic complexity, or rugosity, that is traditionally measured by the chain-and-tape (CT) method. However, to overcome spatial limitations of the CT method, modern studies are moving towards remote sensing data to quantify complexity on a reef-wide scale. Here, we compare rugosity values calculated using the traditional CT method with rugosity values derived from remote sensing, and assess implications of methodological approach for carbonate production estimates. Rugosities derived from remote sensing were calculated from high-resolution (0.1 m) LiDAR bathymetry from two turbid reefs in the Exmouth Gulf, Western Australia, and included virtual chain and tape (VCT), arc–chord ratio (ACR), and surface area to planar area (SAPA). Rugosity values varied significantly between methods (ranges: CT = 1.04–2.15, VCT = 1.01–1.10, ACR and SAPA = 1.00–1.07). Coral carbonate production rates calculated using the CT method were typical of turbid water reefs (2.9 and 3.8 kg m−2 yr−1) which were 30% greater than rates calculated using remote sensing. This variation questions the reliability and comparability of carbonate budgets using remote assessments of reef rugosity with previous budget studies that used the CT method. Given the limitations of remote sensing when capturing fine-scale reef rugosity, we propose that CT is currently a more appropriate method than remote sensing for quantifying rugosity within carbonate budget studies. [ABSTRACT FROM AUTHOR]

Over the last 20,000 years, one third of the continental land mass of Australia, or 2.12 million km2, has been drowned by postglacial sea-level rise. Much of this drowned territory is thought to have been occupied by humans. Where archaeological remains have survived inundation, they can be investigated by underwater and airborne remote sensing, survey, and ground-truthing. This study of the Dampier Archipelago of North West Australia is contextualized by a review of the current state of the art of underwater prehistory. In the absence of known sites, we propose terrestrial analogy as a predictive tool for targeting submerged archaeological sites. Geological and topographic contexts are important for assessing preservation potential as is identifying landforms and features around which people may have focused occupation. Analysis of more than 2,500 known archaeological sites from the extraordinarily rich Dampier Archipelago reveals that the vast majority are rock art sites, but these are interspersed by a significant number of artifact scatters, myriad stone structures, shell middens, and quarry and reduction areas. The majority of these sites are focused on coastal and interior valleys, associated uplands, and coastal embayments. While over two thirds of sites occur on granophyre and basalt substrates, the others are located on Quaternary sediments. Regional research on nearby continental islands shows that use of these environments can be expected to pre-date sea-level rise. The most likely submerged sites include: 1) compacted middens associated with rock pools and estuarine features; 2) stone structures with associated middens on limestone pavements or with granophyre and basalt boulder fields; 3) buried midden and other occupation deposits on protected sand sheets; 4) quarry outcrops, extraction pits, and associated reduction debris in areas of fine-grained granophyre and basalt; and 5) middens in consolidated calcarenite shoreline contexts to the north and west of the volcanic suites of the Dampier Archipelago. [ABSTRACT FROM AUTHOR]

The Dampier Archipelago (Murujuga) is on Australia's National Heritage List because of its significant rock art and numerous stone structures. When people first started living in this arid landscape of the northwest coast, 50,000 years ago, the shoreline was 160 kilometres further north-and west. The Archipelago was created around 7,000 years ago, with sea-level rise following the termination of the Last Glacial Maximum (LGM). Photogrammetry and microphotography (using LiDAR, RPA and Dino-Lite?) are used here to demonstrate how this combination of different scales of imaging can be used to better document the terrestrial Murujuga features record. This paper explores the utility of photogrammetry generated by LiDAR and RPA to locate and reconstruct two types of Aboriginal stone structure (standing stones and house structures) which are prevalent across the Archipelago. These combined techniques were deployed to better visualise and understand site distribution with a view to using the landscape scale methods for the detection of similar features in submerged contexts in the adjacent waters. It has been predicted that this more robust site type would be likely to survive being submerged by sea level rise, and hence this was a site type which we were interested in locating remotely. As well as undertaking systematic terrestrial survey and recording of sample areas across Rosemary Island, topographic LiDAR was flown on two occasions (2017, 2018). These flights were separated by a wildfire which burnt most of the spinifex cover across the island. It highlights the potential - and shortcomings - of remote sensing this type of cultural sites in a naturally rocky and spinifex-covered landscape. It makes recommendations about how to better implement LiDAR to assist in the understanding of the landscape context of these hunter-gatherer stone features. [ABSTRACT FROM AUTHOR]

This article reports Australia's first confirmed ancient underwater archaeological sites from the continental shelf, located off the Murujuga coastline in north-western Australia. Details on two underwater sites are reported: Cape Bruguieres, comprising > 260 recorded lithic artefacts at depths down to −2.4 m below sea level, and Flying Foam Passage where the find spot is associated with a submerged freshwater spring at −14 m. The sites were discovered through a purposeful research strategy designed to identify underwater targets, using an iterative process incorporating a variety of aerial and underwater remote sensing techniques and diver investigation within a predictive framework to map the submerged landscape within a depth range of 0–20 m. The condition and context of the lithic artefacts are analysed in order to unravel their depositional and taphonomic history and to corroborate their in situ position on a pre-inundation land surface, taking account of known geomorphological and climatic processes including cyclone activity that could have caused displacement and transportation from adjacent coasts. Geomorphological data and radiometric dates establish the chronological limits of the sites and demonstrate that they cannot be later than 7000 cal BP and 8500 cal BP respectively, based on the dates when they were finally submerged by sea-level rise. Comparison of underwater and onshore lithic assemblages shows differences that are consistent with this chronological interpretation. This article sets a foundation for the research strategies and technologies needed to identify archaeological targets at greater depth on the Australian continental shelf and elsewhere, building on the results presented. Emphasis is also placed on the need for legislation to better protect and manage underwater cultural heritage on the 2 million square kilometres of drowned landscapes that were once available for occupation in Australia, and where a major part of its human history must lie waiting to be discovered. [ABSTRACT FROM AUTHOR]

In vitro experimental evolution has taught us many lessons on the molecular bases of adaptation. To move towards more natural settings, evolution in the mice gut has been successfully performed. Yet, these experiments suffered from the use of laboratory strains as well as the use of axenic or streptomycin‐treated mice to maintain the inoculated strains. To circumvent these limitations, we conducted a one‐year experimental evolution in vivo using a natural isolate of E. coli, strain 536, in conditions mimicking as much as possible natural environment with mother‐to‐offspring microbiota transmission. Mice were then distributed in 24 independent cages and separated into two different diets: a regular one (chow diet, CD) and high‐fat and high‐sugar one (Western Diet, WD). Genome sequences revealed an early and rapid selection during the breastfeeding period that selected the constitutive expression of the well‐characterized lactose operon. E. coli was lost significantly more in CD than WD; however, we could not detect any genomic signature of selection, nor any diet specificities during the later part of the experiments. The apparently neutral evolution presumably due to low population size maintained nevertheless at high frequency the early selected mutations affecting lactose regulation. The rapid loss of lactose operon regulation challenges the idea that plastic gene expression is both optimal and stable in the wild. [ABSTRACT FROM AUTHOR]

Fire regimes across the globe have been altered through changes in land use, land management, and climate conditions. Understanding how these modified fire regimes impact vegetation structure and dynamics is essential for informed biodiversity conservation and carbon management in savanna ecosystems. We used a fire experiment at the Territory Wildlife Park (TWP), northern Australia, to investigate the consequences of altered fire regimes for vertical habitat structure and above-ground carbon storage. We mapped vegetation three-dimensional (3-D) structure in high spatial resolution with airborne lidar across 18 replicated 1 ha plots of varying fire frequency and season treatments. We used lidar-derived canopy height and cover metrics to extrapolate field-based measures of woody biomass to the full extent of the experimental site (R2=0.82 , RMSE = 7.35 t C ha -1) and analysed differences in above-ground carbon storage and canopy structure among treatments. Woody canopy cover and biomass were highest in the absence of fire (76 % and 39.8 t C ha -1) and lowest in plots burnt late in the dry season on a biennial basis (42 % and 18.2 t C ha -1). Woody canopy vertical profiles differed among all six fire treatments, with the greatest divergence in height classes <5 m. The magnitude of fire effects on vegetation structure varied along the environmental gradient underpinning the experiment, with less reduction in biomass in plots with deeper soils. Our results highlight the large extent to which fire management can shape woody structural patterns in savanna landscapes, even over time frames as short as a decade. The structural profile changes shown here, and the quantification of carbon reduction under late dry season burning, have important implications for habitat conservation, carbon sequestration, and emission reduction initiatives in the region. [ABSTRACT FROM AUTHOR]

The polarimetric L-band imaging synthetic aperture radar (PLIS) is a high spatial resolution (better than 6 m) airborne synthetic aperture radar system that has been dedicated to scientific research into civilian applications since 2010. The weight of PLIS is ∼38 kg, allowing it to be installed aboard small low-cost aircraft, with two antennas used to measure the full backscatter matrix for a swath between 15° and 50° on each side of the flight direction. Calibration based on a total of 96 calibration points and a homogeneous forest during the two recent soil moisture active passive experiments (SMAPEx-4 and 5) showed an overall radiometric accuracy of 0.58 dB (root-mean-square error) over trihedral passive radar calibrators. Independent evaluation based on polarimetric active radar calibrators showed an amplitude imbalance of 0.17 dB with a standard deviation of 0.15 dB and a phase imbalance of 3.87° with a standard deviation of 2.86°. Two calibrated phased-array L-Band synthetic aperture radar-2 (PALSAR-2) images with different observation modes (ScanSAR and Stripmap) were compared with the calibrated PLIS images. The agreement between PALSAR-2 Stripmap and PLIS had a root mean square difference of 1.27 dB and a correlation coefficient of 0.87. Further comparisons over different landcover types confirmed that homogeneous forest and grassland areas constitute optimal targets for cross-validation and/or calibration. [ABSTRACT FROM AUTHOR]

It is evident that using complementary features from different sensors is effective for land cover classification. Therefore, combining complementary information from hyperspectral (HS) and light detection and ranging (LiDAR) data can greatly assist in such applications. In this paper, we propose a model for land cover classification, which extracts effective features representing different characteristics (e.g., spectral, geometrical/structural) of objects of interest from these two complementary data sources (e.g., HS and LiDAR) and fuse them effectively by incorporating dimensionality reduction technique. The HS bands are first grouped based on their joint entropy and structural similarity for group-wise spatial feature extraction. The spectral and spatial features from HS are then fused in parallel via discriminant correlation analysis (DCA) method for each band group. This is followed by a multisource fusion step between the spatial features extracted from HS and LiDAR data using DCA. The resultant features from both band-group fusion and multisource fusion steps are concatenated with several other features extracted from HS and LiDAR data. In the proposed model, DCA fusion produces discriminative features by eliminating between-class correlations and confining within-class correlations. We compare the performance of our feature extraction and fusion scheme using random forest and support vector machine classifiers. We also compare our approach with several state-of-the-art approaches on two benchmark land cover datasets and show that our approach outperforms the alternatives by a large margin. [ABSTRACT FROM AUTHOR]

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Spaceborne laser altimetry waveform estimates of canopy Gap Fraction (GF) vary with respect to discrete return airborne equivalents due to their greater sensitivity to reflectance differences between canopy and ground surfaces resulting from differences in footprint size, energy thresholding, noise characteristics and sampling geometry. Applying scaling factors to either the ground or canopy portions of waveforms has successfully circumvented this issue, but not at large scales. This study develops a method to scale spaceborne altimeter waveforms by identifying which remotely-sensed vegetation, terrain and environmental attributes are best suited to predicting scaling factors based on an independent measure of importance. The most important attributes were identified as: soil phosphorus and nitrogen contents, vegetation height, MODIS vegetation continuous fields product and terrain slope. Unscaled and scaled estimates of GF are compared to corresponding ALS data for all available data and an optimized subset, where the latter produced most encouraging results (R² = 0.89, RMSE = 0.10). This methodology shows potential for successfully refining estimates of GF at large scales and identifies the most suitable attributes for deriving appropriate scaling factors. Large-scale active sensor estimates of GF can establish a baseline from which future monitoring investigations can be initiated via upcoming Earth Observation missions. [ABSTRACT FROM AUTHOR]

Extensive and well-preserved tracksites in the coastally exposed Lower Cretaceous (Valanginian-Barremian) Broome Sandstone of the Dampier Peninsula provide almost the entire fossil record of dinosaurs from the western half of the Australian continent. Tracks near the town of Broome were described in the late 1960s as Megalosauropus broomensis and attributed to a medium-sized theropod trackmaker. Brief reports in the early 1990s suggested the occurrence of at least another nine types of tracks, referable to theropod, sauropod, ornithopod, and thyreophoran trackmakers, at scattered tracksites spread over more than 80 km of coastline north of Broome, potentially representing one of the world's most diverse dinosaurian ichnofaunas. More recently, it has been proposed that this number could be as high as 16 and that the sites are spread over more than 200 km. However, the only substantial research that has been published on these more recent discoveries is a preliminary study of the sauropod tracks and an account of the ways in which the heavy passage of sauropod trackmakers may have shaped the Dampier Peninsula's Early Cretaceous landscape. With the other types of dinosaurian tracks in the Broome Sandstone remaining undescribed, and the full extent and nature of the Dampier Peninsula's dinosaurian tracksites yet to be adequately addressed, the overall scientific significance of the ichnofauna has remained enigmatic. At the request of the area's Goolarabooloo Traditional Custodians, 400C hours of ichnological survey work was undertaken from 2011 to 2016 on the 25 km stretch of coastline in the Yanijarri-Lurujarri section of the Dampier Peninsula, inclusive of the coastline at Walmadany (James Price Point). Forty-eight discrete dinosaurian tracksites were identified in this area, and thousands of tracks were examined and measured in situ and using three-dimensional photogrammetry. Tracksites were concentrated in three main areas along the coast: Yanijarri in the north, Walmadany in the middle, and Kardilakan-Jajal Buru in the south. Lithofacies analysis revealed 16 repeated facies types that occurred in three distinctive lithofacies associations, indicative of an environmental transgression between the distal fluvial to deltaic portions of a large braid plain, with migrating sand bodies and periodic sheet floods. The main dinosaurian track-bearing horizons seem to have been generated between periodic sheet floods that blanketed the preexisting sand bodies within the braid plain portion of a tidally influenced delta, with much of the original, gently undulating topography now preserved over large expanses of the present day intertidal reef system. Of the tracks examined, 150 could be identified and are assignable to a least eleven and possibly as many as 21 different track types: five different types of theropod tracks, at least six types of sauropod tracks, four types of ornithopod tracks, and six types of thyreophoran tracks. Eleven of these track types can formally be assigned or compared to existing or new ichnotaxa, whereas the remaining ten represent morphotypes that, although distinct, are currently too poorly represented to confidently assign to existing or new ichnotaxa. Among the ichnotaxa that we have recognized, only two ( Megalosauropus broomensis and Wintonopus latomorum) belong to existing ichnotaxa, and two compare to existing ichnotaxa but display a suite of morphological features suggesting that they may be distinct in their own right and are therefore placed in open nomenclature. Six of the ichnotaxa that we have identified are new: one theropod ichnotaxon, Yangtzepus clarkei, ichnosp. nov.; one sauropod ichnotaxon, Oobardjidama foulkesi, ichnogen. et ichnosp. nov.; two ornithopod ichnotaxa, Wintonopus middletonae, ichnosp. nov., and Walmadanyichnus hunteri, ichnogen. et ichnosp. nov.; and two thyreophoran ichnotaxa, Garbina roeorum, ichnogen. et ichnosp. nov., and Luluichnus mueckei, ichnogen. et ichnosp. nov. The level of diversity of the main track types is comparable across areas where tracksites are concentrated: Kardilakan-Jajal Buru (12), Walmadany (11), and Yanijarri (10). The overall diversity of the dinosaurian ichnofauna of the Broome Sandstone in the Yanijarri-Lurujarri section of the Dampier Peninsula is unparalleled in Australia, and even globally. In addition to being the primary record of non-avian dinosaurs in the western half of Australia, this ichnofauna provides our only detailed glimpse of Australia's dinosaurian fauna during the first half of the Early Cretaceous. It indicates that the general composition of Australia's mid-Cretaceous dinosaurian fauna was already in place by the Valanginian-Barremian. Both sauropods and ornithopods were diverse and abundant, and thyreophorans were the only type of quadrupedal ornithischians. Important aspects of the fauna that are not seen in the Australian mid-Cretaceous body fossil record are the presence of stegosaurians, an overall higher diversity of thyreophorans and theropods, and the presence of large-bodied hadrosauroid-like ornithopods and very large-bodied sauropods. In many respects, these differences suggest a holdover from the Late Jurassic, when the majority of dinosaurian clades had a more cosmopolitan distribution prior to the fragmentation of Pangea. Although the record for the Lower Cretaceous of Gondwana is sparse, a similar mix of taxa occurs in the Barremian-lower Aptian La Amarga Formation of Argentina and the Berriasian-Hauterivian Kirkwood Formation of South Africa. The persistence of this fauna across the Jurassic-Cretaceous boundary in South America, Africa, and Australia might be characteristic of Gondwanan dinosaurian faunas more broadly. It suggests that the extinction event that affected Laurasian dinosaurian faunas across the Jurassic-Cretaceous boundary may not have been as extreme in Gondwana, and this difference may have foreshadowed the onset of Laurasian-Eurogondwanan provincialism. The disappearance of stegosaurians and the apparent drop in diversity of theropods by the mid-Cretaceous suggests that, similar to South America, Australia passed through a period of faunal turnover between the Valanginian and Aptian. [ABSTRACT FROM AUTHOR]

Across their range, mangroves are responding to coastal environmental change. However, separating the influence of human activities from natural events and processes (including that associated with climatic fluctuation) is often difficult. In the Gulf of Carpentaria, northern Australia (Leichhardt, Nicholson, Mornington Inlet, and Flinders River catchments), changes in mangroves are assumed to be the result of natural drivers as human impacts are minimal. By comparing classifications from time series of Landsat sensor data for the period 1987-2014, mangroves were observed to have extended seawards by up to 1.9 km (perpendicular to the coastline), with inland intrusion occurring along many of the rivers and rivulets in the tidal reaches. Seaward expansion was particularly evident near the mouth of the Leichhardt River, and was associated with peaks in river discharge with Li DAR data indicating distinct structural zones developing following each large rainfall and discharge event. However, along the Gulf coast, and particularly within the Mornington Inlet catchment, the expansion was more gradual and linked to inundation and regular sediment supply through freshwater input. Landward expansion along the Mornington Inlet catchment was attributed to the combined effects of sea level rise and prolonged periods of tidal and freshwater inundation on coastal lowlands. The study concluded that increased amounts of rainfall and associated flooding and sea level rise were responsible for recent seaward and landward extension of mangroves in this region. [ABSTRACT FROM AUTHOR]

The spread of an alien invasive grass (gamba grass-Andropogon gayanus) in the tropical savannas of Northern Australia is a major threat to habitat quality and biodiversity in the region, primarily through its influence on fire intensity. Effective control and eradication of this invader requires better insight into its spatial distribution and rate of spread to inform management actions. We used full-waveform airborne LiDAR to map areas of known A. gayanus invasion in the Batchelor region of the Northern Territory, Australia. Our stratified sampling campaign included wooded savanna areas with differing degrees of A. gayanus invasion and adjacent areas of native grass and woody tree mixtures. We used height and spatial contiguity based metrics to classify returns from A. gayanus and developed spatial representations of A. gayanus occurrence (1 m resolution) and canopy cover (10 m resolution). The cover classification proved robust against two independent field-based investigations at 500 m2 (R2 = 0.87, RMSE = 12.53) and 100 m2 (R2 = 0.79, RMSE = 14.13) scale. Our mapping results provide a solid benchmark for evaluating the rate and pattern of A. gayanus spread from future LiDAR campaigns. In addition, this high-resolution mapping can be used to inform satellite image analysis for the evaluation of A. gayanus invasion over broader regional scales. Our research highlights the huge potential that airborne LiDAR holds for facilitating the monitoring and management of savanna habitat condition. [ABSTRACT FROM AUTHOR]

Savanna ecosystems comprise 22% of the global terrestrial surface and 25% of Australia (almost 1.9 million km2) and provide significant ecosystem services through carbon and water cycles and the maintenance of biodiversity. The current structure, composition and distribution of Australian savannas have coevolved with fire, yet remain driven by the dynamic constraints of their bioclimatic niche. Fire in Australian savannas influences both the biophysical and biogeochemical processes at multiple scales from leaf to landscape. Here, we present the latest emission estimates from Australian savanna biomass burning and their contribution to global greenhouse gas budgets. We then review our understanding of the impacts of fire on ecosystem function and local surface water and heat balances, which in turn influence regional climate. We show how savanna fires are coupled to the global climate through the carbon cycle and fire regimes. We present new research that climate change is likely to alter the structure and function of savannas through shifts in moisture availability and increases in atmospheric carbon dioxide, in turn altering fire regimes with further feedbacks to climate. We explore opportunities to reduce net greenhouse gas emissions from savanna ecosystems through changes in savanna fire management. [ABSTRACT FROM AUTHOR]

Evapotranspiration estimation has benefitted from recent advances in remote sensing and GIS techniques particularly in agricultural applications rather than urban environments. This paper explores the relationship between urban vegetation evapotranspiration (ET) and vegetation indices derived from newly-developed high spatial resolution WorldView-2 imagery. The study site was Veale Gardens in Adelaide, Australia. Image processing was applied on five images captured from February 2012 to February 2013 using ERDAS Imagine. From 64 possible two band combinations of WorldView-2, the most reliable one (with the maximum median differences) was selected. Normalized Difference Vegetation Index (NDVI) values were derived for each category of landscape cover, namely trees, shrubs, turf grasses, impervious pavements, and water bodies. Urban landscape evapotranspiration rates for Veale Gardens were estimated through field monitoring using observational-based landscape coefficients. The relationships between remotely sensed NDVIs for the entire Veale Gardens and for individual NDVIs of different vegetation covers were compared with field measured urban landscape evapotranspiration rates. The water stress conditions experienced in January 2013 decreased the correlation between ET and NDVI with the highest relationship of ET-Landscape NDVI (Landscape Normalized Difference Vegetation Index) for shrubs (r2 = 0.66) and trees (r2 = 0.63). However, when the January data was excluded, there was a significant correlation between ET and NDVI. The highest correlation for ET-Landscape NDVI was found for the entire Veale Gardens regardless of vegetation type (r2 = 0.95, p > 0.05) and the lowest one was for turf (r2 = 0.88, p > 0.05). In support of the feasibility of ET estimation by WV2 over a longer period, an algorithm recently developed that estimates evapotranspiration rates based on the Enhanced Vegetation Index (EVI) from MODIS was employed. The results revealed a significant positive relationship between ETMODIS and ETWV2 (r2 = 0.9857, p > 0.05). This indicates that the relationship between NDVI using high resolution WorldView-2 imagery and ground-based validation approaches could provide an effective predictive tool for determining ET rates from unstressed mixed urban landscape plantings. [ABSTRACT FROM AUTHOR]

ABSTRACT Sediment production, transport and yield were quantified over various timescales in response to rainfall and runoff within an alluvial gully (7 · 8 ha), which erodes into dispersible sodic soils of a small floodplain catchment (33 ha) along the Mitchell River, northern Australia. Historical air photographs and recent global positioning system (GPS) surveys and LiDAR data documented linear increases in gully area and volume, indicating that sediment supply has been relatively consistent over the historic period. Daily time lapse photography of scarp retreat rates and internal erosion processes also demonstrated that erosion from rainfall and runoff consistently supplied fine washload (< 63 µm) sediment in addition to coarse lags of sand bed material. Empirical measurements of suspended sediment concentrations (10 000 to >100 000 mg/L) and sediment yields (89 to 363 t/ha/yr) were high for both Australian and world data. Total sediment yield estimated from empirical washload and theoretical bed material load was dominated by fine washload (< 63 µm). A lack of hysteresis in suspended sediment rating curves, scarp retreat and sediment yield correlated to rainfall input, and an equilibrium channel outlet slope supported the hypothesis that partially or fully transport-limited conditions predominated along the alluvial gully outlet channel. This is in contrast to sediment supply-limited conditions on uneroded floodplains above gully head scarps. While empirical data presented here can support future modelling efforts to predict suspended sediment concentration and yield under the transport limiting situations, additional field data will also be needed to better quantify sediment erosion and transport rates and processes in alluvial gullies at a variety of spatial and temporal scales. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Savannas are highly significant global ecosystems that consist of a mix of trees and grasses and that are highly spatially varied in their physical structure, species composition, and physiological function (i.e., leaf area and function, stem density, albedo, and roughness). Variability in ecosystem characteristics alters biophysical and biogeochemical processes that can affect regional to global circulation patterns, which are not well characterized by land surface models. We initiated a multidisciplinary field campaign called Savanna Patterns of Energy and Carbon Integrated across the Landscape (SPECIAL) during the dry season in Australian savannas to understand the spatial patterns and processes of land surface-atmosphere exchanges (radiation, heat, moisture, CO2, and other trace gasses). We utilized a combination of multiscale measurements including fixed flux towers, aircraft-based flux transects, aircraft boundary layer budgets, and satellite remote sensing to quantify the spatial variability across a continental-scale rainfall gradient (transect). We found that the structure of vegetation changed along the transect in response to declining average rainfall. Tree basal area decreased from 9.6 m2 ha−1 in the coastal woodland savanna (annual rainfall 1,714 mm yr−1) to 0 m2 ha−1 at the grassland site (annual rainfall 535 mm yr−1), with dry-season green leaf area index (LAI) ranging from 1.04 to 0, respectively. Leaf-level measurements showed that photosynthetic properties were similar along the transect. Flux tower measurements showed that latent heat fluxes ( LEs) decreased from north to south with resultant changes in the Bowen ratios ( H/ LE) from a minimum of 1.7 to a maximum of 15.8, respectively. Gross primary productivity, net carbon dioxide exchange, and LE showed similar declines along the transect and were well correlated with canopy LAI, and fluxes were more closely coupled to structure than floristic change. [ABSTRACT FROM AUTHOR]

We demonstrate the efficacy of a commercial portable 2D laser scanner (operating at a wavelength close to 1,000 nm) deployed from a fixed-wing aircraft for measuring the sea surface topography and wave profiles over coastal waters. The LiDAR instrumentation enabled simultaneous measurements of the 2D laser scanner with two independent inertial navigation units, and also simultaneous measurements with a more advanced 2D laser scanner (operating at a wavelength near 1,500 nm). The latter scanner is used routinely for accurately measuring terrestrial topography and was used as a benchmark in this study. We present examples of sea surface topography and wave profiles based on low altitude surveys (< ~300 m) over coastal waters in the vicinity of Cape de Couedic, Kangaroo Island, South Australia and over the surf zone adjacent to the mouth of the Murray River, South Australia. Relative wave heights in the former survey are shown to be consistent with relative wave heights observed from a waverider buoy located near Cape de Couedic during the LiDAR survey. The sea surface topography of waves in the surf zone was successfully mapped with both laser scanners resolving relative wave height variations and fine structure of the sea surface to within approximately 10 cm. A topographic map of the sea surface referenced to the airborne sensor frame transforms to an accurate altimetry map which may be used with airborne electromagnetic instrumentation to provide an averaged altimetry covering a portion of the larger electromagnetic footprint. This averaged altimetry is deemed to be significantly more reliable as a measurement of altimetry than spot measurements using a nadir-looking laser altimeter and would therefore improve upon the use of airborne electromagnetic methods for bathymetric mapping in surf-zone waters. The aperture range of the scanner does not necessarily determine the swath. We observed that instead, the maximum swath at a given altitude was limited by the angle of incidence of the laser at the water surface. [ABSTRACT FROM AUTHOR]

Although the ability to measure vertical eddy fluxes of gases from aircraft platforms represents an important capability to obtain spatially resolved data, accurate and reliable determination of the turbulent vertical velocity presents a great challenge. A nine-hole hemispherical probe known as the “Best Air Turbulence Probe” (often abbreviated as the “BAT Probe”) is frequently used in aircraft-based flux studies to sense the airflow angles and velocity relative to the aircraft. Instruments such as inertial navigation and global positioning systems allow the measured airflow to be converted into the three-dimensional wind velocity relative to the earth’s surface by taking into account the aircraft’s velocity and orientation. Calibration of the aircraft system has previously been performed primarily through in-flight experiments, where calibration coefficients were determined by performing various flight maneuvers. However, a rigorous test of the BAT Probe in a wind tunnel has not been previously undertaken. The authors summarize the results of a complement of low-speed wind tunnel tests and in-flight calibrations for the aircraft–BAT Probe combination. Two key factors are addressed in this paper: The first is the correction of systematic error arising from airflow measurements with a noncalibrated BAT Probe. The second is the instrumental precision in measuring the vertical component of wind from the integrated aircraft-based wind measurement system. The wind tunnel calibration allows one to ascertain the extent to which the BAT Probe airflow measurements depart from a commonly used theoretical potential flow model and to correct for systematic errors that would be present if only the potential flow model were used. The precision in the determined vertical winds was estimated by propagating the precision of the BAT Probe data (determined from the wind tunnel study) and the inertial measurement precision (determined from in-flight tests). The precision of the vertical wind measurement for spatial scales larger than approximately 2 m is independent of aircraft flight speed over the range of airspeeds studied, and the 1σ precision is approximately 0.03 m s-1. [ABSTRACT FROM AUTHOR]

Observations of northward-moving borelike convergence lines over the southern part of the Gulf of Carpentaria region of northern Australia are described. Eleven such disturbances were documented during the 45-day period of the 2002 Gulf Lines Experiment. Of these, six were classified as major and five as minor, depending on their coherence throughout the region. The mean synoptic conditions leading to the two types of events were found to differ. The data for the events provide further insight into the structure and origin of borelike disturbances in the region. Two of the major events, those of 28–29 September and 9 October, are particularly noteworthy. The first of these had a clear double-change structure at all surface stations in the southeastern gulf region with an undular borelike wave preceding and separating from an airmass change in the form of a dryline. It is probably one of the best documented cases of its type. The second, which was documented in unprecedented detail by an instrumented research aircraft, consisted of three separate disturbances: one moving from the southeast, one from the south, and one from the northeast, all of which collided over the gulf. It is believed that the aircraft measurements are the first of their kind anywhere in the world. The aircraft made two long low-level transects through the disturbances and a higher-level transect where they were colliding. Various soundings were also made. The aircraft data showed clearly the undular borelike nature of the southeasterly disturbance. Measured vertical velocities in the waves were as high as 3 m s-1 at a mean altitude of about 230 m. Vertical velocities as high as 5 m s-1 were measured in the region of the collision at an altitude of about 1 km. The longevity of the bores is not explained by the vertical structure of the Scorer parameter, which indicates a leaky waveguide. [ABSTRACT FROM AUTHOR]

Observations of dry-season north Australian cloud lines (NACLs) that form in the Gulf of Carpentaria region of northern Australia and the sea-breeze circulations that initiate them are described. The observations were made during the 2002 Gulf Lines Experiment (GLEX) and include measurements made by an instrumented research aircraft. The observations are compared with numerical simulations made from a two-dimensional cloud-scale model. Particular emphasis is placed on the interaction between the east coast and west coast sea breezes near the west coast of Cape York Peninsula. The sea breezes are highly asymmetric due to the low-level easterly synoptic flow over the peninsula. The west coast sea breeze is well defined with a sharp leading edge since the opposing flow limits its inland penetration, keeping it close to its source of cold air. In contrast, the east coast sea breeze is poorly defined since it is aided by the easterly flow and becomes highly modified by daytime convective mixing as it crosses over the peninsula. Both the observations and the numerical model show that, in the early morning hours, the mature NACL forms at the leading edge of a gravity current. The numerical model simulations show that this gravity current arises as a westward-moving land breeze from Cape York Peninsula. Convergence at the leading edge of this land breeze is accompanied by ascent, which when strong enough produces cloud. Observations show that the decay of the NACL is associated with a decline in the low-level convergence and a weakening of the ascent. [ABSTRACT FROM AUTHOR]