The Greater Houston metropolitan area has experienced recurring flooding events in the past two decades related to tropical cyclones and heavy inland rainfall. With the projected recurrence of severe ...weather events, an approach that outlines the susceptibility of different localities within the study area to potential floods based on analyses of the impacts from earlier events would be beneficial. We applied a novel C-band Sentinel-1 Synthetic Aperture Radar (SAR)-based flood detection method to map floodwater distribution following three recent severe weather events with the goal of identifying areas that are prone to future flood hazards. Attempts were made to calibrate and validate the C-band-based results and analyses to compensate for possible sources of error. These included qualitative and quantitative assessments on L-band aerial SAR data, as well as aerial imagery acquired after one of the events. The findings included the following: (1) most urban centers of Harris county, with few exceptions, are not believed to be prone to flooding hazards in contrast to the densely populated areas on the outskirts of Harris county; (2) nearly 44% of the mapped flood-prone areas lie within a 1 km distance of major drainage networks; (3) areas experiencing high subsidence rates have persistently experienced flooding, possibly exacerbated by morphological changes to the land surface induced by subsidence.
In response to Hurricane Florence of 2018, NASA JPL collected quad-pol L-band SAR data with the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) instrument, observing record-setting river ...stages across North and South Carolina. Fully-polarized SAR images allow for mapping of inundation extent at a high spatial resolution with a unique advantage over optical imaging, stemming from the sensor’s ability to penetrate cloud cover and dense vegetation. This study used random forest classification to generate maps of inundation from L-band UAVSAR imagery processed using the Freeman–Durden decomposition method. An average overall classification accuracy of 87% is achieved with this methodology, with areas of both under- and overprediction for the focus classes of open water and inundated forest. Fuzzy logic operations using hydrologic variables are used to reduce the number of small noise-like features and false detections in areas unlikely to retain water. Following postclassification refinement, estimated flood extents were combined to an event maximum for societal impact assessments. Results from the Hurricane Florence case study are discussed in addition to the limitations of available validation data for accuracy assessments.
The normalized difference vegetation index (NDVI) has been frequently used to map hail damage to vegetation, especially in agricultural areas, but observations can be blocked by cloud cover during ...the growing season. Here, the European Space Agency’s Sentinel-1A/1B C-band synthetic aperture radar (SAR) imagery in co- and cross polarization is used to identify changes in backscatter of corn and soybeans damaged by hail during intense thunderstorm events in the early and late growing season. Following a June event, hail-damaged areas produced a lower mean backscatter when compared with surrounding, unaffected pixels vertical–vertical (VV): −1.1 dB; vertical–horizontal (VH): −1.5 dB. Later, another event in August produced an increase in co- and cross-polarized backscatter (VV: 0.7 dB; VH: 1.7 dB) that is hypothesized to result from the combined effects of crop growth, change in structure of damaged crops, and soil moisture conditions. Hail damage regions inferred from changes in backscatter were further assessed through coherence change detections to support changes in the structure of crops damaged within the hail swath. While studies using NDVI have routinely concluded a decrease in NDVI is associated with damage, the cause of change with respect to the damaged areas in SAR backscatter values is more complex. Influences of environmental variables, such as vegetation structure, vegetation maturity, and soil moisture conditions, need to be considered when interpreting SAR backscatter and will vary throughout the growing season.
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BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Analysis was performed to determine whether a lightning flash could be associated with every reported lightning-initiated wildfire that grew to at least 4 km(exp 2). In total, 905 lightning-initiated ...wildfires within the Continental United States (CONUS) between 2012 and 2015 were analyzed. Fixed and fire radius search methods showed that 81–88% of wildfires had a corresponding lightning flash within a 14 day period prior to the report date. The two methods showed that 52–60% of lightning-initiated wildfires were reported on the same day as the closest lightning flash. The fire radius method indicated the most promising spatial results, where the median distance between the closest lightning and the wildfire start location was 0.83 km, followed by a 75th percentile of 1.6 km and a 95th percentile of 5.86 km. Ninety percent of the closest lightning flashes to wildfires were negative polarity. Maximum flash densities were less than 0.41 flashes km(exp 2) for the 24 h period at the fire start location. The majority of lightning-initiated holdover events were observed in the Western CONUS, with a peak density in north-central Idaho. A twelve day holdover event in New Mexico was also discussed, outlining the opportunities and limitations of using lightning data to characterize wildfires.
The role of the Dingo (variously Canis familiaris, C. familiaris dingo or C. lupus dingo, and hereafter C. dingo) in suppressing Red Fox (Vulpes vulpes) populations in Australia has been ...investigated, with various data tending to show an inverse relationship between densities of the two species (e.g. Letnic et al. 2012; Johnson and VanDerWal 2009). There are very few examples in the literature where direct killing was either observed or inferred (but see Moseby et al. 2012), making each a valuable datapoint. Here, we present a short description of a young adult female Red Fox presumed to have been killed by Dingo in Myall Lakes National Park on the basis of: (1) the close proximity of a Dingo pack (within approximately 20m) to the carcass; (2) the overlap between recorded values of inter-canine distance in Dingo and the wounds on the Red Fox; and (3) the location of those wounds on the body.
Severe weather events including tornadoes, damaging winds, hail, and their combination produce changes in land surface vegetation and urban settings that are frequently observed through remote ...sensing. Capabilities continue to improve through a growing constellation of governmental and commercial assets, increasing the spatial resolution of visible, near to shortwave infrared, and thermal infrared remote sensing. Here, we highlight cases where visual interpretation of imagery benefitted severe weather damage assessments made within the NOAA/NWS Damage Assessment Toolkit. Examples demonstrate utility of imagery in assessing tracks and changes in remote areas where staffing limitations or access prevent a ground-based assessment.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A technique is presented to produce real-time, daily vegetation composites at 0.01 ° resolution ( ~ 1 km) over the Conterminous United States (CONUS) for use in the NASA Land Information System (LIS) ...and weather prediction models. Green vegetation fraction (GVF) is derived from direct-broadcast swaths of normalized difference vegetation index from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the NASA Earth Observing System satellites. The real-time data and increased resolution compared to the 0.144 ° ( ~ 16 km) resolution monthly GVF climatology in community models result in an improved representation of vegetation in high-resolution models, especially in complex terrain. The MODIS GVF fields show seasonal variations that are similar to the community model climatology, and respond realistically to temperature and precipitation anomalies. The wet spring and summer 2010 over the U.S. Plains led to higher regional GVF than in the climatology. The GVF substantially decreased over the U.S. Southern Plains from 2010 to 2011, consistent with the transition to extreme drought in summer 2011. LIS simulations depict substantial sensitivity to the MODIS GVF, with regional changes in heat fluxes around 100 Wm -2 over the northern U.S. in June 2010. CONUS LIS simulations during the 2010 warm season indicate that the larger MODIS GVF in the western U.S. led to higher latent heat fluxes and initially lower sensible heat fluxes, with a net drying effect on the soil. With time, the drier soil eventually lead to higher mean sensible heat fluxes such that the total surface energy output increased by late summer 2010 over the western U.S. A sensitivity simulation of a severe weather event using real-time MODIS GVF data results in systematic changes to low-level temperature, moisture, and instability fields, and improves the evolution of simulated precipitation.
The catastrophic derecho that occurred on 10 August 2020 across the Midwest United States caused billions of dollars of damage to both urban and rural infrastructure as well as agricultural crops, ...most notably across the state of Iowa. This paper documents the complex evolution of the derecho through the use of low-Earth orbit passive-microwave imager and GOES-16satellite-derived products complemented by products derived from NEXRAD weather radar observations. Additional satellite sensors including optical imagers and synthetic aperture radar (SAR) were used to observe impacts to the power grid and agriculture in Iowa. SAR improved the identification and quantification of damaged corn and soybeans, as compared to true-color composites and Normalized Difference Vegetation Index (NDVI). A statistical approach to identify damaged corn and soybean crops from SAR was created with estimates of 1.97 million acres of damaged corn and 1.40 million acres of damaged soybeans in the state of Iowa. The damage estimates generated by this study were comparable to estimates produced by others after the derecho, including two commercial agricultural companies.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Intracapsular femoral neck fractures are associated with decreased cortical width and increased proportions of Haversian canals with diameters greater than the normal mean plus 3 SD (i.e., >385 μm). ...Such canals might be formed if closely associated resorbing osteons merge; a cortical event analogous with the loss of cancellous connectivity. To test this, we investigated the pattern of osteon distribution in the aging femoral neck to determine if remodeling osteons were distributed in anatomical clusters. Femoral neck biopsies from female patients with intracapsular hip fractures (n = 13) were compared with age/gender-matched cadaveric controls (n = 13). Solochrome-stained sections were analyzed for Haversian canal location, canal diameter, and the presence of an osteoid surface. Clustering was investigated using statistical software with a cluster defined as two or more osteoid-bearing osteon centers within 0.75 mm of each other. Clusters occurred more frequently than would be expected by chance (
p < 0.001). Fracture cases had more clusters per unit area (3.14 ± 0.31 clusters/25 mm
2 of cortical bone) than controls (1.89 ± 0.22) (
p = 0.002). In fracture cases, the antero-inferior, antero-superior, and infero-anterior regions had more clusters per 25 mm
2 than comparable control regions (ant/inf: 4.12 ± 0.79, 1.70 ± 0.60,
p = 0.025; ant/sup: 5.31 ± 1.1, 1.80 ± 0.59,
p = 0.013; inf/ant: 3.15 ± 0.49, 1.27 ± 0.29,
p = 0.004). The mean number of clusters per 25 mm
2 per region correlated with the mean porosity per region (adjusted r
2 = 0.60;
p = 0.014), and the total number of giant canals per region correlated with the total number of clusters per region (adjusted r
2 = 0.58;
p = 0.011). In conclusion, remodeling osteons are clustered or grouped anatomically, and fracture cases have more clusters than controls. Our data suggest that merging of adjacent, clustered osteons during resorption could lead to the rapid development of canals with excessive diameters and focal weakness. Clustering is greatest in those regions that we have previously shown to have the largest relative reductions in bone strength compared with controls and known to be maximally loaded during a sideways fall. This implicates the remodeling process underlying clustering of remodeling osteons in the aetiology of hip fracture.
It has been suggested that, in hip fracture, the cortex on the inferoanterior (IA) to superoposterior (SP) axis is thinned and shows increased porosity. This is dependent on the presence of giant ...canals (i.e., diameter >385 μm), which are related to clusters of remodeling osteons. To investigate further the relationship between remodeling and bone loss, osteonal diameter (On.Dm), wall thickness (W.Th), osteoid width (O.Wi), and extent (OS) were measured in femoral neck biopsies from 12 female intracapsular hip fracture cases and 11 age- and gender-matched controls. Over 83% of giant canals were “composite” osteonal systems in which a single canal was surrounded by multiple packets of osteonal bone. Among smaller canals, over 80% of systems had a canal encircled by a single cement line containing one packet of bone (“simple”). Composites were nearly twice as prevalent in fractures (fracture cases 9.8 ± 0.7/25 mm
2, controls 5.3 ± 0.4/25 mm
2,
p < 0.0001), and were dependent (
R
2 = 0.52) on femoral neck region (
p = 0.0008) and the regional distribution of clusters of remodeling osteons (
p = 0.0045). Both the inferior (I) and anterior (A) regions had an elevated number of composites (I: 263% of control values,
p = 0.0054; A: 202% of control values,
p = 0.0092). On.Dm was similar in fracture cases and controls (simple: fracture cases 183 ± 3 μm, controls 191 ± 4 μm; composites: fracture cases 446 ± 13 μm, controls 460 ± 13 μm). W.Th in simples was similar in fracture cases and controls (fracture cases 51 ± 0.8 μm, controls 49 ± 0.7 μm), but composites had significantly (
p < 0.0001) thinner walls, with the reduction in fracture cases (31%) being twice that of controls (12%,
p < 0.0001). There were no differences in O.Wi. It was unusual for osteoid to fully surround the composite canal surface; OS was 38% lower in composite than simple canals (
p < 0.0001). This study indicates that, in the femoral neck cortex, the principal remodeling deficit in hip fracture is specific to composite osteons. Hip fracture cases had zonal increases in composite osteon density with reduced bone formation. The data suggest that generation of composite osteons is a plausible mechanism leading to increasing porosity and trabecularization of the cortex, thus weakening the cortex in regions maximally loaded on fall impact.
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