Lower Great Plains Research Articles

Being African American and Rural: A Double Jeopardy From COVID-19.

Being African American and Rural: A Double Jeopardy From COVID-19.

Comparison of Historical and Recent Fish Distribution Patterns in Oklahoma and Western Arkansas

In the past century and a half, surface waters in the lower Great Plains have been impacted by numerous factors related to human settlement and development of the region including construction of reservoirs, which have been well documented to have negative effects on stream fish communities. In Oklahoma, by 1925 there were only seven artificial impoundments (of 36–970 hectares), but by 2007 there were 146 impoundments in the state lake registry ranging up to 42,000 hectares. Most were built from the 1930s to the 1970s. We examined historic and recent distribution patterns of fishes in Oklahoma and western Arkansas using data from 86 collections made by A. I. Ortenburger from 1925–1927 and from 381 collections we made from 1975–2009 in the same region, to ask if faunal changes were apparent following the era of dam construction. Although exact sites in the 1920s and in 1975–2009 were not identical, there were collections in 14 Hydrologic Units (HUCs as identified by eight-digit Hydrologic Unit Codes) in th...

Predicting the elements

On 20 May this year, a massive and powerful tornado hit Moore, Oklahoma. With peak winds of 340km/h, the 2km wide tornado tore through the heavily populated town on a 27km long path across the Oklahoma City region, killing 24 people and ripping down 13,000 homes, schools, farms and businesses. Water supplies were cut, more than 61,500 power outages were registered and Oklahoma Department for Insurance estimates claims will top $1bn. This twister was one of 53 in a large, violent weather system that swept across the midwestern United States and lower Great Plains from 18 to 21 May, killing two more people. What's more, this spate of tornadoes came only a day after a 23-strong outbreak that spanned Texas, Louisiana and Alabama, killing six people. Set these against a back-drop of hurricanes, earthquakes, floods, and tsunamis that take place worldwide, year in, year out, and one fact becomes very clear; each and every extreme weather event is so very difficult to predict.

Fortis and lenis obstruents in English

The primary contrast between obstruents in English has been described in alternative ways: either /p, t, t∫, k, f, θ, s, ∫/ are voiceless and /b, d, d3, g, v, ð, z, 3/ voiced, or the former set is fortis and the latter lenis. This paper reviews the phonetic properties of fortis sounds and draws together both published and new arguments for a basic fortis/lenis contrast in English obstruents. Rules are presented for phonetic and phonological alternations involving English obstruents, and it is shown that stressed vowel shortening, final glottalization, and aspiration are all properties of fortis obstruents while certain devoicings and final cluster simplifications operate on lenis obstruents. Schwa devoicing is also related to consonant strength. It is argued that a fortis/lenis analysis provides a more general explanation of a wider range of phenomena than the voiced/voiceless analysis and that voicing is predictable from fortis and lenis properties. Two sound changes in English, the [θ/ð] split and the development of an initial implosive in Lower Great Plains English, are shown to require the fortis/lenis analysis, as is Notker's Law in Old High German, suggesting that the fortis/lenis contrast is quite old in Germanic. Finally it is argued that fortis and lenis obstruents form natural classes and that a feature [fortis] must be added to the root node of the feature tree.

Temporal Stability of Minnow Species Co-Occurrence in Streams of the Central United States

Abstract We examined temporal stability of minnow species co-occurrence using four sets of collections made by seining in streams of the central United States. These collections were made at spatial scales ranging from within a single watershed to across a six-state region of the lower Great Plains, and over time periods ranging from 17 to 75 years. A Jaccard's index of co-occurrence based on presence-absence was calculated for all possible species pairs across all sites for each set of collections. Stability of co-occurrence patterns was assessed using Mantel tests to compare co-occurrence matrices for sequential collections. Within a single watershed (Piney Creek, Izard County, Arkansas) patterns of co-occurrence at 12 sites were correlated highly across sequential collections (r = 0.618 to 0.871, n = 9), suggesting that species associations within the watershed are stable and predictable. Within the Red River basin (Red and Washita rivers), correlations of co-occurrence patterns at six sites were varia...

Diurnal Oscillations of Low-Level Jets, Vertical Motion, and Precipitation: A Model Case Study

Abstract Heavy convection that occurred over Tulsa, Oklahoma, during the evening and night of 26/27 May 1984 is studied through a series of numerical experiments with a regional forecast model. The emphasis is on diurnal oscillations of the boundary-layer flow and the sensitivity of model predictions of nocturnal low-level jets to the presence or absence of cloud radiative interaction and latent heating. The nocturnal low-level jet appears to be established mainly by boundary-layer processes and to be significantly amplified by the latent heat of condensation, which increases during the night over the lower Great Plains. The presence of cloud radiative interactions appears to have less impact on the prediction of the low-level jet and nocturnal convection for the present case, but it is important for the timing of the nocturnal precipitation. The regional model underestimates the extreme precipitation rates observed over Tulsa. The possibility that this underestimation is a consequence of insufficient res...

Tropospheric chemistry over the lower Great Plains of the United States. 1. Meteorology

Convective clouds and thunderstorms inject planetary boundary layer air with high concentrations of ozone (O3) and O3 precursors into the free troposphere. By altering the chemistry and radiative balance of the upper troposphere, these local actions can have global consequences. In order to extrapolate from individual observations to general trends we have devised a method to identify weather patterns conducive to convection in the southern or lower Great Plains in early summer and applied this method to meteorological and chemical data from a series of research flights carried out in June 1985. Previous studies have noted that weather patterns in the lower Great Plains in this season are characterized by alternating pulses of polar and maritime air masses and very frequent episodes of violent convection, usually in maritime conditions in advance of a surface cold front or along the frontal zone itself. In this study, a set of selection criteria is applied to surface and upper air meteorological data from central Oklahoma to distinguish the two meridional phases characteristic of this region: maritime and polar. A deep layer of moist, southerly flow and convective instability is encountered in the maritime regime, while the polar phase is convectively stable throughout the midtroposphere and much less conducive to convection. For the period 1980–1985 both maritime and polar regimes occur with a frequency of about 35% in May, while the maritime phase becomes dominant in June (53% maritime versus 20% polar). Within the maritime regime, conditions conducive to the development of severe storms are characterized by the presence of a dry, low‐level inversion that tends to inhibit scattered midday convection over a wide region while simultaneously enhancing the probability of larger thunderstorms and mesoscale convective systems. This “modified maritime” category accounts for approximately 25% of the total cases in May and in June. The instances of frontal passage account for approximately 15% of the total cases. Profiles, from the surface to 200 mbar, made on 18 flights of the NCAR Sabreliner in the 1985 PRESTORM project, are categorized according to the selection criteria. Part 2 of this study presents representative concentrations of ozone, carbon monoxide, and reactive nitrogen compounds as a function of altitude (0–12 km) for each category and discusses the implications of these findings.