Tornado folk science in Alabama and Mississippi in the 27 April 2011 tornado outbreak

In this paper, we collect, categorize, and discuss the existence of numerous ways of knowing about tornado threat that largely differ from the perspective taken by the meteorological community. These alternate ways of knowing became apparent during interviews with survivors of the 27 April 2011 tornado outbreak in the US southeast, particularly in Alabama and Mississippi. Phenomena discussed herein include perceptions of safety near waterways, vulnerability near a specific highway with a recently modified landscape, the protective nature of hills, relative optimism about home sites, and local observational weather knowledge. Theoretical explanations offered for these observed phenomena include ideas from risk perception and place attachment literatures.     

Physical modeling of near-Earth Asteroid (29075) 1950 DA

Near-Earth Asteroid (29075) 1950 DA may closely encounter Earth in 2880. The probability of Earth impact may be as high as 1/300, but the outcome of the encounter depends critically on the physical properties of the asteroid [Giorgini et al., 2002. Science 196, 132-136]. We have used Arecibo and Goldstone radar data and optical lightcurves to estimate the shape, spin state, and surface structure of 1950 DA. The data allow two distinct models. One rotates prograde and is roughly spheroidal with mean diameter 1.16±0.12 km. The other rotates retrograde and is oblate and about 30% larger. Both models suggest a nickel-iron or enstatite chondritic composition. Ground-based observations should be able to determine which model is correct within the next several decades.     

Use of turbidometry to characterize suspended sediment and phosphorus fluxes in the Lake Tahoe basin,California, USA

The efficacy of in‐stream nephelometric turbidometry as a surrogate for total suspended solids (TSS) and total phosphorus (TP) concentrations was evaluated for use in low turbidity (<50 NTU) subalpine watersheds at Lake Tahoe, California–Nevada, USA. Continuous turbidity records for the 1999, 2000 and 2001 snowmelt seasons and data from water quality samples (1982–2000) were examined to determine watershed sediment delivery dynamics. Strong correlations were found between turbidity and both TSS and TP concentration. The strong correlation indicates that turbidity can serve as a good surrogate for direct measurement in these watersheds. The watersheds displayed clockwise hysteresis: sediment flushing and depletion, on daily, seasonal and decadal time‐scales. The hysteresis curves had strong concave shapes, indicating a sensitive response to peak flow. A pronounced seasonal trend was observed for the ratio of suspended sediment concentration (SSC)/discharge over time, indicating early season flushing of available sediment. Significant linear relationships (p < 0·05) were found for 12 of 17 years. Comparison of annual sediment rating curve coefficients indicated smaller coefficients during high sediment loading years and in the years following. The smaller coefficients are evidence of sediment depletion during high flow years. The effect of hysteresis on monitoring methods was illustrated by comparing turbidity estimates of TSS load with sediment rating curve estimates of SSC. After accounting for differences in SSC/TSS methods of analysis, daily loads calculated with turbidity methods were 58–98% of rating curve estimates for the spring snowmelt seasons of 1999–2001. Copyright © 2006 John Wiley & Sons, Ltd.     

Lagrangian air mass tracking with smart balloons during ACE‐2

A 3rd‐generation smart balloon designed at National Oceanic and Atmospheric Administration, Air Resources Laboratory Field Research Division, in collaboration with the University of Hawaii, was released from ship‐board during the recent Second Aerosol Characterization Experiment (ACE‐2) to provide Lagrangian air‐mass tracking data. ACE‐2 is the 3rd in a series of field experiments designed to study the chemical, physical, and radiative properties and processes of atmospheric aerosols and their role in climate and is organized by the international global atmospheric chemistry (IGAC) program. The adjective smart in the title of this paper refers to the fact that the buoyancy of the balloon automatically adjusts through the act of pumping air into or releasing air from the ballast portion of the balloon when it travels vertically outside a barometric pressure range set prior to release. The smart balloon design provides GPS location, barometric pressure, temperature, relative humidity, and other data via a transponder to a C130 research aircraft flying in the vicinity of the balloon. The addition of 2‐way communication allows interactive control of the balloon operating parameters by an observer. A total of 3 cloudy Lagrangian experiments were conducted during the ACE‐2 field program which lasted from 16 June through 26 July 1997. This paper reviews the design and capability of the smart balloons and their performance during the ACE‐2 Lagrangian experiments. Future development and applications of the technology are discussed.     

Petrography and geochemistry of five new Apollo 16 mare basalts and evidence for post‐basin deposition of basaltic material at the site

Abstract— We present the petrography and geochemistry of five 2–4 mm basalt fragments from the Apollo 16 regolith. These fragments are 1) a high‐Ti vitrophyric basalt compositionally similar to Apollo 17 high‐Ti mare basalts, 2) a very high‐Ti vitrophyric basalt compositionally similar to Apollos 12 and 14 red‐black pyroclastic glass, 3) a coarsely crystalline high‐Al basalt compositionally similar to group 5 Apollo 14 high‐Al mare basalts, 4) a very low‐Ti (VLT) crystalline basalt compositionally similar to Luna 24 VLT basalts, and 5) a VLT basaltic glass fragment compositionally similar to Apollo 17 VLT basalts. High‐Ti basalt has been reported previously at the Apollo 16 site; the other basalt types have not been reported previously. As there are no known cryptomaria or pyroclastic deposits in the highlands near the Apollo 16 site (ruling out a local origin), and scant evidence for basaltic material in the Apollo 16 ancient regolith breccias or Apollo 16 soils collected near North Ray Crater (ruling out a basin ejecta origin), we infer that the basaltic material in the Apollo 16 regolith originated in maria near the Apollo 16 site and was transported laterally to the site by small‐ to medium‐sized post‐basin impacts. On the basis of TiO₂ concentrations derived from the Clementine UVVIS data, Mare Tranquillitatis (?300 km north) is the most likely source for the high‐Ti basaltic material at the Apollo 16 site (craters Ross, Arago, Dionysius, Maskelyne, Moltke, Sosigenes, Schmidt), Mare Nectaris/Sinus Asperitatis (?220 km east) is the most likely source for the low‐Ti and VLT basaltic material (craters Theophilus, Madler, Torricelli), and a large regional pyroclastic deposit near Mare Vaporum (?600 km northwest) is the most likely source region for pyroclastic material (although no source craters are apparent in the region).     

Spatially and temporally distributed modeling of landslide susceptibility

Mapping of landslide susceptibility in forested watersheds is important for management decisions. In forested watersheds, especially in mountainous areas, the spatial distribution of relevant parameters for landslide prediction is often unavailable. This paper presents a GIS-based modeling approach that includes representation of the uncertainty and variability inherent in parameters. In this approach, grid-based tools are used to integrate the Soil Moisture Routing (SMR) model and infinite slope model with probabilistic analysis. The SMR model is a daily water balance model that simulates the hydrology of forested watersheds by combining climate data, a digital elevation model, soil, and land use data. The infinite slope model is used for slope stability analysis and determining the factor of safety for a slope. Monte Carlo simulation is used to incorporate the variability of input parameters and account for uncertainties associated with the evaluation of landslide susceptibility. This integrated approach of dynamic slope stability analysis was applied to the 72-km² Pete King watershed located in the Clearwater National Forest in north-central Idaho, USA, where landslides have occurred. A 30-year simulation was performed beginning with the existing vegetation covers that represented the watershed during the landslide year. Comparison of the GIS-based approach with existing models (FSmet and SHALSTAB) showed better precision of landslides based on the ratio of correctly identified landslides to susceptible areas. Analysis of landslide susceptibility showed that (1) the proportion of susceptible and non-susceptible cells changes spatially and temporally, (2) changed cells were a function of effective precipitation and soil storage amount, and (3) cell stability increased over time especially for clear-cut areas as root strength increased and vegetation transitioned to regenerated forest. Our modeling results showed that landslide susceptibility is strongly influenced by natural processes and human activities in space and time; while results from simulated outputs show the potential for decision-making in effective forest planning by using various management scenarios and controlling factors that influence landslide susceptibility. Such a process-based tool could be used to deal with real-dynamic systems to help decision-makers to answer complex landslide susceptibility questions.     

Spatial Prediction of Landslide Hazard Using Logistic Regression and ROC Analysis

An empirical modeling of road related and non‐road related landslide hazard for a large geographical area using logistic regression in tandem with signal detection theory is presented. This modeling was developed using geographic information system (GIS) and remote sensing data, and was implemented on the Clearwater National Forest in central Idaho. The approach is based on explicit and quantitative environmental correlations between observed landslide occurrences, climate, parent material, and environmental attributes while the receiver operating characteristic (ROC) curves are used as a measure of performance of a predictive rule. The modeling results suggest that development of two independent models for road related and non‐road related landslide hazard was necessary because spatial prediction and predictor variables were different for these models. The probabilistic models of landslide potential may be used as a decision support tool in forest planning involving the maintenance, obliteration or development of new forest roads in steep mountainous terrain.     

Arsenic distribution, speciation and solubility in shallow groundwater of Owens Dry Lake, California

Generation of dust particles from the Owens Lake playa creates a severe air pollution hazard in the western United States. Much of the dust produced from the dry lakebed is derived from salts formed by evaporation of saline groundwater that often contains high concentrations of dissolved arsenic (As). The objectives of this research were to study the spatial distribution of dissolved arsenic in the shallow groundwater, and to examine factors affecting arsenic solubility and speciation. Evapoconcentration, redox potential, pH, and mineral solubility were examined as factors regulating arsenic biogeochemistry. Dissolved arsenic concentrations ranged from 0.1 to 96 mg L⁻¹ and showed a general increase from the shoreline to the center of the lakebed. Arsenic concentrations were strongly correlated to electrical conductivity (EC) and δD suggesting that evapoconcentration is an important process regulating total As concentrations. Arsenite [As(III)] was the dominant form of inorganic arsenic at Eh values less than about −170 mV while arsenate [As(V)] was predominant at higher Eh values. Organic arsenic was negligible (<0.21%) in all shallow groundwater samples. Dissolved arsenic concentrations do not appear to be strongly regulated by solid-phase reactions. Solid-phase arsenic concentrations generally ranged between 4.0 and 42.6 mg kg⁻¹ and a maximum concentration range (20 to 40 mg kg⁻¹) was reached as solution concentration increased up to 80 mg L⁻¹, indicating minimal sorption and/or precipitation of arsenic. Chemical equilibrium modeling indicated that orpiment (As₂S₃) was the only solid phase with a positive saturation index (indicating over-saturation), but only at high arsenic and sulfide concentrations. The findings of this research are important for assessing the potential environmental impacts of elevated arsenic concentrations on dust mitigation efforts taking place at Owens Dry Lake.     

Concentrations of unsubstituted polycyclic aromatic hydrocarbons in softshell clams from Coos Bay,Oregon, USA

Concentrations of benzo[a]pyrene (BAP) were measured in subpopulations of softshell clams, Mya arenaria, from four intertidal sites in Coos Bay from June 1976 to June 1978. Subsequently, concentrations of 15 unsubstituted polynuclear aromatic hydrocarbons (PNAH) were determined in two subpopulations from September 1978 to August 1979. There were significant differences between BAP concentrations in clams from the four sites. For the two-year period, they were highest in clams inhabiting areas adjacent to the industrialized bayfront and lowest in clams inhabiting more remote areas. There were no significant seasonal variations in BAP concentrations during this period. During the 1978–1979 study, the average total PNAH concentration in clams from the bayfront area was 555.1 μg kg^?1 compared to 76.3 μg kg^?1 for clams from a more remote environment. In general, PNAH concentrations were lowest in the fall-winter and highest during the spring-summer.     

Focused infiltration of snowmelt water in partially frozen soil under small depressions

Ephemeral puddles in small closed depressions can play an important role in the hydrology and ecology of many landscapes, by storing runoff water, recharging soil moisture and shallow groundwater, and by providing food and habitat for many organisms. Infiltration of snowmelt water under small depressions (<1000 m²) has been studied in the St. Denis National Wildlife Area in Saskatchewan, Canada, located within the northern glaciated prairie of North America where numerous depressions of varying sizes exist. The depressions stored most of the snowmelt runoff generated within their respective watersheds. The water level in a typical depression declined at 0.6 mm/h while the underlying frozen soil was thawing. This rate was likely limited by the rate of downward movement of the thawing front, which was functioning as a moving impermeable boundary. The rate of thawing was controlled by the external energy input from the ground surface. Standing water in depressions efficiently trapped incoming radiation and conducted it to the thawing front. The recession rate increased to 1.1 mm/h when the soil under the depression thawed completely. The recession rate at this later stage appears to be limited by the hydraulic conductivity of the subsoil (0.04–4 mm/h), which is much smaller than the topsoil conductivity (10–20 mm/h).