scholarly journals Climatic Variability of Near-Surface Turbulent Kinetic Energy over the United States: Implications for Fire-Weather Predictions

2013 ◽  
Vol 52 (4) ◽  
pp. 753-772 ◽  
Author(s):  
Warren E. Heilman ◽  
Xindi Bian
Keyword(s):  
United States ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Atmospheric Turbulence ◽  
Climatic Variability ◽  
Fire Behavior ◽  
The United States ◽  
Spatial And Temporal Variability ◽  
Fire Weather ◽  
Near Surface

AbstractRecent research suggests that high levels of ambient near-surface atmospheric turbulence are often associated with rapid and sometimes erratic wildland fire spread that may eventually lead to large burn areas. Previous research has also examined the feasibility of using near-surface atmospheric turbulent kinetic energy (TKEs) alone or in combination with the Haines index (HI) as an additional indicator of anomalous atmospheric conditions conducive to erratic or extreme fire behavior. However, the application of TKEs-based indices for operational fire-weather predictions in the United States on a regional or national basis first requires a climatic assessment of the spatial and temporal patterns of the indices that can then be used for testing their operational effectiveness. This study provides an initial examination of some of the spatial and temporal variability patterns across the United States of TKEs and the product of HI and TKEs (HITKEs) using data from the North American Regional Reanalysis dataset covering the 1979–2008 period. The analyses suggest that there are regional differences in the behavior of these indices and that regionally dependent threshold values for TKEs and HITKEs may be needed for their potential use as operational indicators of anomalous atmospheric turbulence conditions conducive to erratic fire behavior. The analyses also indicate that broad areas within the northeastern, southeastern, and southwestern regions of the United States have experienced statistically significant positive trends in TKEs and HITKEs values over the 1979–2008 period, with the most substantial increases in values occurring over the 1994–2008 period.

Turbulent kinetic energy during wildfires in the north central and north-eastern US

2010 ◽  
Vol 19 (3) ◽  
pp. 346 ◽  
Author(s):  
Warren E. Heilman ◽  
Xindi Bian
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Quantitative Measure ◽  
Fire Weather ◽  
Fire Behaviour ◽  
Weather Index ◽  
Fire Weather Index ◽  
Near Surface ◽  
North Eastern

The suite of operational fire-weather indices available for assessing the atmospheric potential for extreme fire behaviour typically does not include indices that account for atmospheric boundary-layer turbulence or wind gustiness that can increase the erratic behaviour of fires. As a first step in testing the feasibility of using a quantitative measure of turbulence as a stand-alone fire-weather index or as a component of a fire-weather index, simulations of the spatial and temporal patterns of turbulent kinetic energy during major recent wildfire events in the western Great Lakes and north-eastern US regions were performed. Simulation results indicate that the larger wildfires in these regions of the US were associated with episodes of significant boundary-layer ambient turbulence. Case studies of the largest recent wildfires to occur in these regions indicate that the periods of most rapid fire growth were generally coincident with occurrences of the product of the Haines Index and near-surface turbulent kinetic energy exceeding a value of 15 m2 s–2, a threshold indicative of a highly turbulent boundary layer beneath unstable and dry atmospheric layers, which is a condition that can be conducive to erratic fire behaviour.

scholarly journals Diurnal Dynamics of the Umov Kinetic Energy Density Vector in the Atmospheric Boundary Layer from Minisodar Measurements

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1347
Author(s):  
Alexander Potekaev ◽  
Nikolay Krasnenko ◽  
Liudmila Shamanaeva
Keyword(s):  
Energy Density ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Energy Flux ◽  
Wind Effect ◽  
Kinetic Energy Density ◽  
Near Surface ◽  
Density Vector ◽  
The Mean ◽  
Umov Vector

The diurnal hourly dynamics of the kinetic energy flux density vector, called the Umov vector, and the mean and turbulent components of the kinetic energy are estimated from minisodar measurements of wind vector components and their variances in the lower 200-meter layer of the atmosphere. During a 24-hour period of continuous minisodar observations, it was established that the mean kinetic energy density dominated in the surface atmospheric layer at altitudes below ~50 m. At altitudes from 50 to 100 m, the relative contributions of the mean and turbulent wind kinetic energy densities depended on the time of the day and the sounding altitude. At altitudes below 100 m, the contribution of the turbulent kinetic energy component is small, and the ratio of the turbulent to mean wind kinetic energy components was in the range 0.01–10. At altitudes above 100 m, the turbulent kinetic energy density sharply increased, and the ratio reached its maximum equal to 100–1000 at altitudes of 150–200 m. A particular importance of the direction and magnitude of the wind effect, that is, of the direction and magnitude of the Umov vector at different altitudes was established. The diurnal behavior of the Umov vector depended both on the time of the day and the sounding altitude. Three layers were clearly distinguished: a near-surface layer at altitudes of 5–15 m, an intermediate layer at altitudes from 15 m to 150 m, and the layer of enhanced turbulence above. The feasibility is illustrated of detecting times and altitudes of maximal and minimal wing kinetic energy flux densities, that is, time periods and altitude ranges most and least favorable for flights of unmanned aerial vehicles. The proposed novel method of determining the spatiotemporal dynamics of the Umov vector from minisodar measurements can also be used to estimate the effect of wind on high-rise buildings and the energy potential of wind turbines.

Compatibility of Passenger Vehicles and Cable Median Barrier Systems

2017 ◽  
Author(s):  
Cody S. Stolle ◽  
John D. Reid
Keyword(s):  
United States ◽  
Kinetic Energy ◽  
The United States ◽  
Detailed Data ◽  
Factors Affecting ◽  
Passenger Vehicles ◽  
Complicating Factors ◽  
Departments Of Transportation ◽  
Severe Type ◽  
Trajectory Angle

Cross-median crashes are one of the most severe type of highway crashes. Many state Departments of Transportation (DOTs) install median barriers, such as cable median barriers (CMBs), to reduce the rate of cross-median crashes. Nonetheless, these barriers are not always successful. Approximately 20,000 cable barrier crashes throughout the United States spanning between 1999 and 2010 were examined, and detailed data was sufficient to determine the prevailing causes of 182 penetration crashes (i.e., barrier was breached). Penetration crashes involving CMBs were affected by: (1) impact conditions; (2) barrier placement and design; and (3) vehicle factors, including geometry and inertial properties. In general, CMB crashes occur at higher CG trajectory angles than with other roadside features. The 85th percentile CG trajectory angle for cable barriers was 39 degrees, compared to 25 degrees when all roadside features are considered. Approximately 2.2% of all CMB crashes were severe, although penetrations were between two and thirteen times more likely to be severe than non-penetration crashes. Vehicle factors such as weight and geometrical profile affected the likelihood of CMB penetrations. Headlights or taillights fractured or were damaged in approximately 80% of non-penetration crashes, but were damaged or fractured in less than 60% of penetration crashes, often by additional unrelated impacts. Lastly, heavier vehicles with more kinetic energy were more likely than similar, lighter vehicles to penetrate CMBs. Through better understanding of all of the complicating factors affecting CMB performance, better designs and guidelines can be prepared to maximize CMB effectiveness.

scholarly journals 692. Effects of Regional Climatic Variability on West Nile Virus Outbreaks in the United States

2018 ◽  
Vol 5 (suppl_1) ◽  
pp. S249-S250
Author(s):  
Raghesh Varot Kangath ◽  
Buddhika Maduraperuma ◽  
Juliana Souza Borges ◽  
Rajasreepai Ramachandrapai
Keyword(s):  
United States ◽  
High Temperature ◽  
Population Density ◽  
Climatic Variability ◽  
The United States ◽  
Climatic Data ◽  
Cca Ordination ◽  
Neuroinvasive Disease ◽  
South Central ◽  
Risk Areas

Abstract Background Transmission of WNV to humans in the United States typically occurs between June and September since warm temperatures accelerate mosquito life cycle. Precipitation can cause increase in aquatic breeding but outbreaks often depends upon human water management. We examine epidemiology, patterns of WNV disease transmission, and identification of high-risk areas in the United States from 2003 to 2014. Methods Trends and relationships of WNV cases and climatic factors were analyzed among the regions of the United States from 2003 to 2014. Human WNV tabulate data and climatic data were obtained from Centers for Disease Control, and NOAA and Climate Data Guide, respectively. Canonical correspondence analysis (CCA) was performed using variables: (i) neuroinvasive disease cases, non-neuroinvasive disease cases, deaths, presumptiveviremic blood donors, (ii) precipitation, temperature, Palmer Drought Severity Index (PDSI) and population density. The CCA ordination was explained the variability between WNV disease cases andclimatic variables. Biplots were used to visualize the associations between WNV cases and climatic anomalies. Results We compared the state wise WNV disease cases in relation to climatic and population density in the United States from 2003 to 2014. A total of 4,064 cases in 2006, 956 cases in 2010 and, 2,141 cases in 2014 were reported in the 32 states of the United States. Colorado state reported the highest WNV cases in 2003 (2,947 cases; 33%), followed by Texas in 2012 (1,868 cases; 35%) and California in 2014 (801 case; 37%). CCA ordination showed distinguishable clustering patterns between south central (Texas, Louisiana, Mississippi, Arkansas, and Oklahoma) and northern Great Plains (North Dakota, South Dakota, and Nebraska) regions (Figure 1). High temperature and prolong drought were the most important variable predictor for high WNV outbreak. Conclusion Vector control methods focusing on prevention must be implemented to avoid epidemics of WNV if high temperature is leading to an unusual drought especially at the risk areas, such as Texas and California. However, high temperature with moist spell anomalies in the south central region showed a negative influence on WNV outbreak. Disclosures All authors: No reported disclosures.

Homogenized Variability of Radiosonde-Derived Atmospheric Boundary Layer Height over the Global Land Surface from 1973 to 2014

2016 ◽  
Vol 29 (19) ◽  
pp. 6893-6908 ◽  
Author(s):  
Xiaoyan Wang ◽  
Kaicun Wang
Keyword(s):  
United States ◽  
Boundary Layer ◽  
Time Series ◽  
Land Surface ◽  
Statistical Significance ◽  
Potential Temperature ◽  
The United States ◽  
Near Surface ◽  
Layer Height ◽  
Boundary Layer Height

Abstract Boundary layer height (BLH) significantly impacts near-surface air quality, and its determination is important for climate change studies. Integrated Global Radiosonde Archive data from 1973 to 2014 were used to estimate the long-term variability of the BLH based on profiles of potential temperature, relative humidity, and atmospheric refractivity. However, this study found that there was an obvious inhomogeneity in the radiosonde-derived BLH time series because of the presence of discontinuities in the raw radiosonde dataset. The penalized maximal F test and quantile-matching adjustment were used to detect the changepoints and to adjust the raw BLH series. The most significant inhomogeneity of the BLH time series was found over the United States from 1986 to 1992, which was mainly due to progress made in sonde models and processing procedures. The homogenization did not obviously change the magnitude of the daytime convective BLH (CBLH) tendency, but it improved the statistical significance of its linear trend. The trend of nighttime stable BLH (SBLH) is more dependent on the homogenization because the magnitude of SBLH is small, and SBLH is sensitive to the observational biases. The global daytime CBLH increased by about 1.6% decade−1 before and after homogenization from 1973 to 2014, and the nighttime homogenized SBLH decreased by −4.2% decade−1 compared to a decrease of −7.1% decade−1 based on the raw series. Regionally, the daytime CBLH increased by 2.8%, 0.9%, 1.6%, and 2.7% decade−1 and the nighttime SBLH decreased significantly by −2.7%, −6.9%, −7.7%, and −3.5% decade−1 over Europe, the United States, Japan, and Australia, respectively.

An Evaluation of NDFD Weather Forecasts for Wildland Fire Behavior Prediction

2018 ◽  
Vol 33 (1) ◽  
pp. 301-315 ◽  
Author(s):  
Wesley G. Page ◽  
Natalie S. Wagenbrenner ◽  
Bret W. Butler ◽  
Jason M. Forthofer ◽  
Chris Gibson
Keyword(s):  
United States ◽  
Wind Speed ◽  
Relative Humidity ◽  
Air Temperature ◽  
Wildland Fire ◽  
Fire Behavior ◽  
The United States ◽  
Mean Bias Error ◽  
Bias Error ◽  
Behavior Prediction

Abstract Wildland fire managers in the United States currently utilize the gridded forecasts from the National Digital Forecast Database (NDFD) to make fire behavior predictions across complex landscapes during large wildfires. However, little is known about the NDFDs performance in remote locations with complex topography for weather variables important for fire behavior prediction, including air temperature, relative humidity, and wind speed. In this study NDFD forecasts for calendar year 2015 were evaluated in fire-prone locations across the conterminous United States during periods with the potential for active fire spread using the model performance statistics of root-mean-square error (RMSE), mean fractional bias (MFB), and mean bias error (MBE). Results indicated that NDFD forecasts of air temperature and relative humidity performed well with RMSEs of about 2°C and 10%–11%, respectively. However, wind speed was increasingly underpredicted when observed wind speeds exceeded about 4 m s−1, with MFB and MBE values of approximately −15% and −0.5 m s−1, respectively. The importance of accurate wind speed forecasts in terms of fire behavior prediction was confirmed, and the forecast accuracies needed to achieve “good” surface head fire rate-of-spread predictions were estimated as ±20%–30% of the observed wind speed. Weather station location, the specific forecast office, and terrain complexity had the largest impacts on wind speed forecast error, although the relatively low variance explained by the model (~37%) suggests that other variables are likely to be important. Based on these results it is suggested that wildland fire managers should use caution when utilizing the NDFD wind speed forecasts if high wind speed events are anticipated.

scholarly journals Shortwave Radiative Fluxes on Slopes

2016 ◽  
Vol 55 (7) ◽  
pp. 1513-1532
Author(s):  
Yingtao Ma ◽  
Rachel T. Pinker ◽  
Margaret M. Wonsick ◽  
Chuan Li ◽  
Laura M. Hinkelman
Keyword(s):  
United States ◽  
Snow Cover ◽  
Spatial Resolution ◽  
Snow Water Equivalent ◽  
The United States ◽  
Spatial And Temporal Variability ◽  
Remotely Sensed Data ◽  
Radiative Fluxes ◽  
Attractive Option ◽  
Moderate Resolution Imaging Spectroradiometer

AbstractSnow-covered mountain ranges are a major source of water supply for runoff and groundwater recharge. Snowmelt supplies as much as 75% of the surface water in basins of the western United States. Net radiative fluxes make up about 80% of the energy balance over snow-covered surfaces. Because of the large extent of snow cover and the scarcity of ground observations, use of remotely sensed data is an attractive option for estimating radiative fluxes. Most of the available methods have been applied to low-spatial-resolution satellite observations that do not capture the spatial variability of snow cover, clouds, or aerosols, all of which need to be accounted for to achieve accurate estimates of surface radiative fluxes. The objective of this study is to use high-spatial-resolution observations that are available from the Moderate Resolution Imaging Spectroradiometer (MODIS) to derive surface shortwave (0.2–4.0 μm) downward radiative fluxes in complex terrain, with attention on the effect of topography (e.g., shadowing or limited sky view) on the amount of radiation received. The developed method has been applied to several typical melt seasons (January–July during 2003, 2004, 2005, and 2009) over the western part of the United States, and the available information was used to derive metrics on spatial and temporal variability of shortwave fluxes. Issues of scale in both the satellite and ground observations are also addressed to illuminate difficulties in the validation process of satellite-derived quantities. It is planned to apply the findings from this study to test improvements in estimation of snow water equivalent.

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