Development and Evaluation of High Resolution Simulation Tools to Improve Fire Weather Forecasts

Fire weather forecasts rely on numerical weather simulations where the grid size is 4 km x 4 km or larger. In areas of complex terrain, this model resolution will not capture the details of wind flows associated with complicated topography. Wind channeling in valleys, wind speed-up over mountains and ridges, and enhanced turbulence associated with rough terrain and tall forest canopies are poorly represented in current weather model applications. A number of numerical wind flow models have been developed for simulating winds at high resolution; however, there are limited observational data available at the spatial scales appropriate for evaluating these types of models. In response to this need for high resolution validation data, we collected wind measurements at very high spatial resolution over a range of meteorological conditions from three different types of terrain/landcover features: an isolated mountain covered predominantly by grass and sagebrush, a steep river canyon covered predominantly by grass, and a dissected montane drainage with a tall forest canopy. We used data from the isolated mountain and the steep river canyon to evaluate surface wind predictions from routine weather forecasts and a high resolution wind simulation model, WindNinja, developed specifically for fire behavior applications. Data from the third field site will be used for future model evaluations planned to investigate the effect of tall forest canopies on surface wind predictions. Analyses of observations from the isolated mountain and steep river canyon sites indicate that operational weather model (i.e., with numerical grid resolutions of around 4 km or larger) wind predictions are not likely to be good predictors of local near-surface winds (i.e., at sub-grid scales) in complex terrain. Under periods of weak synoptic forcing, surface winds tended to be decoupled from large-scale flows, and under periods of strong synoptic forcing, variability in surface winds was sufficiently large due to terrain-induced mechanical effects that a large-scale mean flow would not be representative of surface winds at most locations on or within the terrain feature. These findings are reported in a manuscript titled “High Resolution Observations of the Near-Surface Wind Field over an Isolated Mountain and in a Steep River Canyon” submitted for publication in Atmospheric Chemistry and Physics. Links to the observed data from this effort as well as an online interface to query, visualize, summarize, and download subsets of the data are available at: http://www.firemodels.org/index.php/windninja-introduction/windninja-publications. Findings from the model evaluations work indicate that using WindNinja to downscale from numerical weather prediction (NWP) model winds can, in some cases, improve the accuracy of surface wind forecasts in complex terrain. Predictions of surface wind speeds and directions improved with downscaling via WindNinja when flow features induced by large scale effects were adequately captured by the NWP model used to initialize WindNinja. This suggests that WindNinja could be incorporated into current fire forecast methods to provide better short-term forecasts for fire management operations. These findings are reported in a manuscript titled “Downscaling Surface Wind Predictions from Numerical Weather Prediction Models in Complex Terrain with a Mass-consistent Wind Model” that will be submitted to the Journal of Applied Meteorology and Climatology later this spring

Development and Evaluation of High Resolution Simulation Tools to Improve Fire Weather Forecasts

Fire weather forecasts rely on numerical weather simulations where the grid size is 4 km x 4 km or larger. In areas of complex terrain, this model resolution will not capture the details of wind flows associated with complicated topography. Wind channeling in valleys, wind speed-up over mountains and ridges, and enhanced turbulence associated with rough terrain and tall forest canopies are poorly represented in current weather model applications. A number of numerical wind flow models have been developed for simulating winds at high resolution; however, there are limited observational data available at the spatial scales appropriate for evaluating these types of models. In response to this need for high resolution validation data, we collected wind measurements at very high spatial resolution over a range of meteorological conditions from three different types of terrain/landcover features: an isolated mountain covered predominantly by grass and sagebrush, a steep river canyon covered predominantly by grass, and a dissected montane drainage with a tall forest canopy. We used data from the isolated mountain and the steep river canyon to evaluate surface wind predictions from routine weather forecasts and a high resolution wind simulation model, WindNinja, developed specifically for fire behavior applications. Data from the third field site will be used for future model evaluations planned to investigate the effect of tall forest canopies on surface wind predictions. Analyses of observations from the isolated mountain and steep river canyon sites indicate that operational weather model (i.e., with numerical grid resolutions of around 4 km or larger) wind predictions are not likely to be good predictors of local near-surface winds (i.e., at sub-grid scales) in complex terrain. Under periods of weak synoptic forcing, surface winds tended to be decoupled from large-scale flows, and under periods of strong synoptic forcing, variability in surface winds was sufficiently large due to terrain-induced mechanical effects that a large-scale mean flow would not be representative of surface winds at most locations on or within the terrain feature. These findings are reported in a manuscript titled “High Resolution Observations of the Near-Surface Wind Field over an Isolated Mountain and in a Steep River Canyon” submitted for publication in Atmospheric Chemistry and Physics. Links to the observed data from this effort as well as an online interface to query, visualize, summarize, and download subsets of the data are available at: http://www.firemodels.org/index.php/windninja-introduction/windninja-publications. Findings from the model evaluations work indicate that using WindNinja to downscale from numerical weather prediction (NWP) model winds can, in some cases, improve the accuracy of surface wind forecasts in complex terrain. Predictions of surface wind speeds and directions improved with downscaling via WindNinja when flow features induced by large scale effects were adequately captured by the NWP model used to initialize WindNinja. This suggests that WindNinja could be incorporated into current fire forecast methods to provide better short-term forecasts for fire management operations. These findings are reported in a manuscript titled “Downscaling Surface Wind Predictions from Numerical Weather Prediction Models in Complex Terrain with a Mass-consistent Wind Model” that will be submitted to the Journal of Applied Meteorology and Climatology later this spring

Hydrologic and Erosion Responses to Wildfire Along the Rangeland-Xeric Forest Continuum in the Western US: A Review and Model of Hydrologic Vulnerability

The recent increase in wildfire activity across the rangeland–xeric forest continuum in the western United States has landscape-scale consequences in terms of runoff and erosion. Concomitant cheatgrass (Bromus tectorum L.) invasions, plant community transitions and a warming climate in recent decades along grassland–shrubland–woodland–xeric forest transitions have promoted frequent and large wildfires, and continuance of the trend appears likely if warming climate conditions prevail. These changes potentially increase overall hydrologic vulnerability by spatially and temporally increasing soil exposure to runoff and erosion processes. Plot and hillslope-scale studies demonstrate burning may increase event runoff or erosion by factors of 2–40 over small-plot scales and more than 100-fold over large-plot to hillslope scales. Reports of flooding and debris flow events from rangelands and xeric forests following burning show the potential risk to natural resources, property, infrastructure and human life. We present a conceptual model for evaluating post-fire hydrologic vulnerability and risk. We suggest that post-fire risk assessment of potential hydrologic hazards should adopt a probability-based approach that considers varying site susceptibility in conjunction with a range of potential storms and that determines the hydrologic response magnitudes likely to affect values-at-risk. Our review suggests that improved risk assessment requires better understanding in several key areas including quantification of interactions between varying storm intensities and measures of site susceptibility, the varying effects of soil water repellency, and the spatial scaling of post-fire hydrologic response across rangeland–xeric forest plant communities

THE RESPONSE OF MECHANORECEPTORS IN RAT SKIN TO BIAXIAL LOADING: A PRELIMINARY STUDY

ABSTRACT Mechanoreceptor neurons were studied in an isolated rat skin preparation subjected to dynamic biaxial stretch. The strength of the relationship between neuronal responses and mechanical variables was determined using multiple logistic regression. The experimental protocol allowed the normal stresses as well as the maximum shear stress to be manipulated. In n=4 neurons, response was associated with the time rate of change of normal stress and this response was affected by the direction of loading. There was no relationship between response and the value of maximum shear stress. There was a strong association with the rate of change of maximum shear stress. INTRODUCTION Mechanoreceptors are sensory neurons that are activated by mechanical stimulation of soft tissues. There are large numbers of mechanoreceptors in skin, and virtually all of them can be activated by stretch stimuli. Stretching skin alters the states of both stress and strain. Work in our laboratory has focused on determining the coupling between stretch-evoked responses in cutaneous neurons and the stress and strain components of stretch stimuli. Recently

Structural and Functional Connectivity as a Driver of Hillslope Erosion Following Disturbance

Hydrologic response to rainfall on fragmented or burnt hillslopes is strongly influenced by the ensuing connectivity of runoff and erosion processes. Yet cross-scale process connectivity is seldom evaluated in field studies owing to scale limitations in experimental design. This study quantified surface susceptibility and hydrologic response across point to hillslope scales at two degraded unburnt and burnt woodland sites using rainfall simulation and hydrologic modelling. High runoff (31–47 mm) and erosion (154–1893 g m–2) measured at the patch scale (13 m2) were associated with accumulation of fine-scale (0.5-m2) splash-sheet runoff and sediment and concentrated flow formation through contiguous bare zones (64–85% bare ground). Burning increased the continuity of runoff and sediment availability and yield. Cumulative runoff was consistent across plot scales whereas erosion increased with increasing plot area due to enhanced sediment detachment and transport. Modelled hillslope-scale runoff and erosion reflected measured patch-scale trends and the connectivity of processes and sediment availability. The cross-scale experiments and model predictions indicate the magnitude of hillslope response is governed by rainfall input and connectivity of surface susceptibility, sediment availability, and runoff and erosion processes. The results demonstrate the importance in considering cross-scale structural and functional connectivity when forecasting hydrologic and erosion responses to disturbances

Designing tools to predict and mitigate impacts on water quality following the Australian 2019/2020 wildfires: Insights from Sydney's largest water supply catchment

The 2019/2020 Australian bushfires (or wildfires) burned the largest forested area in Australia's recorded history, with major socio-economic and environmental consequences. Among the largest fires was the 280 000 ha Green Wattle Creek Fire, which burned large forested areas of the Warragamba catchment. This protected catchment provides critical ecosystem services for Lake Burragorang, one of Australia's largest urban supply reservoirs delivering ~85% of the water used in Greater Sydney. Water New South Wales (WaterNSW) is the utility responsible for managing water quality in Lake Burragorang. Its postfire risk assessment, done in collaboration with researchers in Australia, the UK, and United States, involved (i) identifying pyrogenic contaminants in ash and soil; (ii) quantifying ash loads and contaminant concentrations across the burned area; and (iii) estimating the probability and quantity of soil, ash, and associated contaminant entrainment for different rainfall scenarios. The work included refining the capabilities of the new WEPPcloud-WATAR-AU model (Water Erosion Prediction Project cloud-Wildfire Ash Transport And Risk-Australia) for predicting sediment, ash, and contaminant transport, aided by outcomes from previous collaborative postfire research in the catchment. Approximately two weeks after the Green Wattle Creek Fire was contained, an extreme rainfall event (~276 mm in 72 h) caused extensive ash and sediment delivery into the reservoir. The risk assessment informed on-ground monitoring and operational mitigation measures (deployment of debris-catching booms and adjustment of the water supply system configuration), ensuring the continuity of safe water supply to Sydney. WEPPcloud-WATAR-AU outputs can prioritize recovery interventions for managing water quality risks by quantifying contaminants on the hillslopes, anticipating water contamination risk, and identifying areas with high susceptibility to ash and sediment transport. This collaborative interaction among scientists and water managers, aimed also at refining model capabilities and outputs to meet managers' needs, exemplifies the successful outcomes that can be achieved at the interface of industry and science. Integr Environ Assess Manag 2021;17:1151–1161. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).During manuscript preparation J. Neris, C. Santin, R. Lew, and S.H. Doerr were supported by a Natural Environment Research Council grant (NE/R011125/1)

Protection from erosion following wildfire

Abstract. Erosion in the first year after a wildfire can be up to three orders of magnitude greater than the erosion from undisturbed forests. To mitigate potential postfire erosion, various erosion control treatments are applied on highly erodible areas with downstream resources in need of protection. Because postfire erosion rates generally decline by an order of magnitude for each year of recovery, effective erosion mitigation treatments are most needed during the first year or two after a fire. Postfire treatments include broadcast seeding, scarification and trenching, physical erosion barriers such as contour-felled logs and straw wattles, and mulching with wheat straw, wood straw, and hydromulch. This paper summarizes data from more than seven years of studies to evaluate the effectiveness of postfire erosion mitigation treatments at the hillslope and small watershed-scale in the western U.S. Results suggest that some mitigation treatments may help reduce erosion for some, but not all, rainfall events. Generally, mulching is more effective than seeding, scarifying, or erosion barriers. For small rainfall events, reduction in first year erosion rates have been measured for engineered wood straw and straw mulch (60 to 80%), contour-felled log erosion barriers (50 to 70%), and hydromulch (19%). Grass seeding treatments have little effect on first year erosion reduction. For intense rain events (I 10 greater than 40 mm h -1 ) there was little difference between treated and non-treated areas

Incorporating Hydrologic Data and Ecohydrologic Relationships into Ecological Site Descriptions

The purpose of this paper is to recommend a framework and methodology for incorporating hydrologic data and ecohydrologic relationships in Ecological Site Descriptions (ESDs) and thereby enhance the utility of ESDs for assessing rangelands and guiding resilience-based management strategies. Resilience-based strategies assess and manage ecological state dynamics that affect state vulnerability and, therefore, provide opportunities to adapt management. Many rangelands are spatially heterogeneous or sparsely vegetated where the vegetation structure strongly influences infiltration and soil retention. Infiltration and soil retention further influence soil water recharge, nutrient availability, and overall plant productivity. These key ecohydrologic relationships govern the ecologic resilience of the various states and community phases on many rangeland ecological sites (ESs) and are strongly affected by management practices, land use, and disturbances. However, ecohydrologic data and relationships are often missing in ESDs and state-and-transition models (STMs). To address this void, we used literature to determine the data required for inclusion of key ecohydrologic feedbacks into ESDs, developed a framework and methodology for data integration within the current ESD structure, and applied the framework to a select ES for demonstrative purposes. We also evaluated the utility of the Rangeland Hydrology and Erosion Model (RHEM) for assessment and enhancement of ESDs based in part on hydrologic function. We present the framework as a broadly applicable methodology for integrating ecohydrologic relationships and feedbacks into ESDs and resilience-based management strategies. Our proposed framework increases the utility of ESDs to assess rangelands, target conservation and restoration practices, and predict ecosystem responses to management. The integration of RHEM technology and our suggested framework on ecohydrologic relations expands the ecological foundation of the overall ESD concept for rangeland management and is well aligned with resilience-based, adaptive management of US rangelands. The proposed enhancement of ESDs will improve communication between private land owners and resource managers and researchers across multiple disciplines in the field of rangeland management

Discovery of biphenylacetamide-derived inhibitors of BACE1 using de novo structure-based molecular design

β-Secretase (BACE1), the enzyme responsible for the first and rate-limiting step in the production of amyloid-β peptides, is an attractive target for the treatment of Alzheimer’s disease. In this study, we report the application of the de novo fragment-based molecular design program SPROUT to the discovery of a series of nonpeptide BACE1 inhibitors based upon a biphenylacetamide scaffold. The binding affinity of molecules based upon this designed molecular scaffold was increased from an initial BACE1 IC50 of 323 μM to 27 μM following the synthesis of a library of optimized ligands whose structures were refined using the recently developed SPROUT-HitOpt software. Although a number of inhibitors were found to exhibit cellular toxicity, one compound in the series was found to have useful BACE1 inhibitory activity in a cellular assay with minimal cellular toxicity. This work demonstrates the power of an in silico fragment-based molecular design approach in the discovery of novel BACE1 inhibitors