Climate Change Impacts for the Conterminous USA: An Integrated Assessment

Here we simulate dryland agriculture in the United States in order to assess potential future agricultural production under a set of general circulation model (GCM)-based climate change scenarios. The total national production of three major grain crops—corn, soybeans, and winter wheat—and two forage crops—alfalfa and clover hay—is calculated for the actual present day core production area (CPA) of each of these crops. In general, higher global mean temperature (GMT) reduces production and higher atmospheric carbon dioxide concentration ([CO₂]) increases production. Depending on the climatic change scenarios employed overall national production of the crops studied changes by up to plus or minus 25% from present-day levels. Impacts are more significant regionally, with crop production varying by greater than ±50% from baseline levels. Analysis of currently possible production areas (CPPAs) for each crop indicates that the regions most likely to be affected by climate change are those on the margins of the areas in which they are currently grown. Crop yield variability was found to be primarily influenced by local weather and geographic features rather than by large-scale changes in climate patterns and atmospheric composition. Future US agronomic potential will be significantly affected by the changes in climate projected here. The nature of the crop response will depend primarily on to what extent precipitation patterns change and also on the degree of warming experienced.     

A Comparison of Wolf's Reconstructed Record of Annual Sunspot Number with Schwabe's Observed Record of ‘Clusters of Spots’ for the Interval of 1826–1868

Samuel Heinrich Schwabe, the discoverer of the sunspot cycle, observed the Sun routinely from Dessau, Germany during the interval of 1826–1868, averaging about 290 observing days per year. His yearly counts of ‘clusters of spots’ (or, more correctly, the yearly number of newly appearing sunspot groups) provided a simple means for describing the overt features of the sunspot cycle (i.e., the timing and relative strengths of cycle minimum and maximum). In 1848, Rudolf Wolf, a Swiss astronomer, having become aware of Schwabe's discovery, introduced his now familiar ‘relative sunspot number’ and established an international cadre of observers for monitoring the future behavior of the sunspot cycle and for reconstructing its past behavior (backwards in time to 1818, based on daily sunspot number estimates). While Wolf's reconstruction is complete (without gaps) only from 1849 (hence, the beginning of the modern era), the immediately preceding interval of 1818–1848 is incomplete, being based on an average of 260 observing days per year. In this investigation, Wolf's reconstructed record of annual sunspot number is compared against Schwabe's actual observing record of yearly counts of clusters of spots. The comparison suggests that Wolf may have misplaced (by about 1–2 yr) and underestimated (by about 16 units of sunspot number) the maximum amplitude for cycle 7. If true, then, cycle 7's ascent and descent durations should measure about 5 years each instead of 7 and 3 years, respectively, the extremes of the distributions, and its maximum amplitude should measure about 86 instead of 70. This study also indicates that cycle 9's maximum amplitude is more reliably determined than cycle 8's and that both appear to be of comparable size (about 130 units of sunspot number) rather than being significantly different. Therefore, caution is urged against the indiscriminate use of the pre-modern era sunspot numbers in long-term studies of the sunspot cycle, since such use may lead to specious results.     

1999年海城-岫岩地震序列的精准定位

1999年11月29日,北京时间12点10分39秒(04:10:39 UTC)在我国辽宁海城-岫岩地区发生了一次Ms5.4地震.这次地震是继1975年2月4日海城Ms7.3地震之后该地区发生的震级最大的一次地震.区域性的辽宁数字地震台网记录了这一序列的前震、主震与 余震.本文运用该台网的记录资料,用双差法对海城-岫岩地...     

Effectiveness of post-fire salvage logging stream buffer management for hillslope erosion in the U.S. Inland Northwest Mountains

Active wildfire seasons in the western U.S. warrant the evaluation of post-fire forest management strategies. Ground-based salvage logging is often used to recover economic loss of burned timber. In unburned forests, ground-based logging often follows best management practices by leaving undisturbed areas near streams called stream buffers. However, the effectiveness of these buffers has not been tested in a post-wildfire setting. This experiment tested buffer width effectiveness with a novel field-simulated rill experiment using sediment-laden runoff (25 g/L) released over 40 min at evenly timed flow rates (50, 100 and 150 L/min) to measure surface runoff travel length and sediment concentration under unburned and high and low soil burn severity conditions at 2-, 10- and 22-month post-fire. High severity areas 2-month post-fire had rill lengths of up to 100 m. Rill length significantly decreased over time as vegetation regrowth provided ground cover. Sediment concentration and sediment dropout rate also varied significantly by soil burn severity. Sediment concentrations were 19 g/L for the highest flow 2-month post-fire and reduced to 6.9–14 g/L 10-month post-fire due to abundant vegetation recovery. The amount of sediment dropping out of the flow consistently increased over the study period with the low burn severity rate of 1.15 g L⁻¹ m⁻¹ approaching the unburned rate of 1.29 g L⁻¹ m⁻¹ by 2-year post-fire. These results suggest that an often-used standard, 15 m buffer, was sufficient to contain surface runoff and reduce sediment concentration on unburned sites, however buffers on high burn severity sites need to be eight times greater (120 m) immediately after wildfire and four times greater (60 m) 1-year post-fire. Low burn severity areas 1-year post-fire may need to be only twice the width of an unburned buffer (30 m), and 2-year post-fire these could return to unburned widths.     

Arsenic and antimony in geothermal waters of Yellowstone National Park,Wyoming, USA

A total of 268 thermal spring samples were analyzed for total soluble As using reduced molybdenum-blue; 27 of these samples were also analyzed for total Sb using flame atomic absorption spectrometry. At Yellowstone the $\text{Cl}\text{As}$ atomic ratio is nearly constant among neutral-alkaline springs with Cl > 100 mg L^?1, and within restricted geographic areas, indicating no differential effects of adiabatic vs. conductive cooling on arsenic. The $\text{Cl}\text{As}$ ratio increases with silica and decreases with decreasing $\text{Cl}\text{ΣCO}{}_3$; the latter relationship is best exemplified for springs along the extensively sampled SE-NW trend within the Lone Star-Upper-Midway Basin region. The relationship between $\text{Cl}\text{As}$ and $\text{Cl}\text{ΣCO}{}_3$ at Yellowstone suggests a possible rock leaching rather than magmatic origin for much of the Park's total As flux. Condensed vapor springs are low in both As and Cl. Very high $\text{Cl}\text{As}$ ratios ( > 1000) are associated exclusively with highly diluted (Cl < 100 mg L^?1) mixed springs in the Norris and Shoshone Basins and in the Upper White Creek and Firehole Lake areas of Lower Basin. The high ratios are associated with acidity and/or oxygen and iron; they indicate precipitation of As following massive dilution of the Asbearing high-Cl parent water.Yellowstone Sb ranged from 0.009 at Mammoth to 0.166 mg L^?1 at Joseph's Coat Spring. Within basins, the $\text{Cl}\text{Sb}$ ratio increases as the $\text{Cl}\text{ΣCO}{}_3$ ratio decreases, in marked contrast to As. Mixed springs also have elevated $\text{Cl}\text{Sb}$ ratios. White (1967) and Weissberg (1969) previously reported stibnite (Sb₂S₃), but not orpiment (As₂S₃), precipitating in the near surface zone of alkaline geothermal systems.     

The rotation of active regions with differing magnetic polarity separations

The separation of the leading and following portions of plages and (multi-spot) sunspot groups is examined as a parameter in the analysis of plage and spot group rotation. The magnetic complexity of plages affects their average properties in such a study because it tends to make the polarity separations of the plages less than they really are (by the definition of polarity separation used here). Correcting for this effect, one finds a clear and very significant dependence of the total magnetic flux of a region on its polarity separation. Extrapolating this relationship to zero total flux leads to an X intercept of about 25 Mm in polarity separation. The average residual rotation rates of regions depend upon the polarity separation in the sense that larger separations correspond to slower rotation rates (except for small values of separation, which are affected by region complexity). In the case of sunspots, the result that smaller individual spots rotate faster than larger spots is confirmed and quantified. It is shown also that smaller spot groups rotate faster than larger groups, but this is a much weaker effect than that for individual spots. It is suggested that the principal effect is for spots, and that this individual spot effect is responsible for much or all of the group effect, including that attributed in the past to group age. Although larger spot groups have larger polarity separations, it is shown that the rotation rate-polarity separation effect is the opposite in groups than one finds in plages: groups with larger polarity separations rotate faster than those with smaller separations. This anomalous effect may be related to the evolution of plages and spot groups, or it may be related to connections with subsurface toroidal flux tubes. It is suggested that the polarity separation is a parameter of solar active regions that may shed some light on their origin and evolution.Operated by the Association of Universities for Research in Astronomy, Inc., under Cooperative Agreement with the National Science Foundation.     

First record of an arthropod from the Passaic Formation (Late Triassic), near Milford, New Jersey

Mudstones of the Triassic Passaic Formation, near Milford, New Jersey, have yielded the first evidence of an arthropod impression in that formation. Associated trace fossils include Helminthoidichnites, Lockeia, Scoyenia, Spongeliomorpha, and the reptile footprint Rhynchosauroides, representing the Scoyenia ichnofacies. Associated sedimentary structures include desiccation cracks and raindrop impressions. The Passaic sediments were deposited under shallow water lacustrine shoreline conditions subject to periodic subaerial exposure.     

Probabilistic correction of RCM precipitation in the Basque Country (Northern Spain)

A parametric quantile–quantile transformation is used to correct the systematic errors of precipitation projected by regional climate models. For this purpose, we used two new probability distributions: modified versions of the Gumbel and log-logistic distributions, which fit to the precipitation of both wet and dry days. With these tools, the daily probability distribution of seven regional climate models was corrected: Aladin-ARPEGE, CLM-HadCM3Q0, HIRHAM-HadCM3Q0, HIRHAM-BCM, RECMO-ECHAM5-rt3, REMO-ECHAM-rt3 and PROMES-HadCM3Q0. The implemented method presents an error less than 5 % in the simulation of the average precipitation and 1 % in the simulation of the number of dry days. For the study area, an intensification of daily and subdaily precipitation is expected under the A1B scenario throughout the 21st century. This intensification is interpreted as a consequence of the process of ‘mediterraneanisation’ of the most southern ocean climate.     

Relationship of atmospheric ozone profiles to solar magnetic activity

The observed relationship between atmospheric vorticity variations and solar magnetic sector boundary passages is examined for a possible connection via ionization changes affecting ozone distributions. A superposed epoch analysis was performed on Umkehr distributions for 18 years from Arosa, Switzerland, with use of more than 500 solar sector boundary passages as keyday zero. No significant responses are observed in any Umkehr level or in total observed ozone amounts. Further analyses on shorter records for Belsk, Poland, and Hohenpeissenberg, West Germany, corroborate these results. Another analysis for Arosa with about 100 type IV solar flares as keyday zero also shows no definitive trend. It is concluded that ozone distribution changes cannot be the primary causative mechanism for vorticity variations.Journal Paper No. J-8838 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1852.     

Field-Scale Evaluation of Bioaugmentation Dosage for Treating Chlorinated Ethenes

A field demonstration was performed to evaluate the impacts of bioaugmentation dosage for treatment of chlorinated ethenes in a sandy-to-silty shallow aquifer. Specifically, bioaugmentation using a commercially available Dehalococcoides (DHC)-containing culture was performed in three separate groundwater recirculation loops, with one loop bioaugmented with 3.9 × 10¹¹ DHC, the second loop bioaugmented with 3.9 × 10¹² DHC, and the third loop bioaugmented with 3.9 × 10¹³ DHC. Groundwater monitoring was performed to evaluate DHC growth and migration, dechlorination rates, and aquifer geochemistry. The loop inoculated with 3.9 × 10¹² DHC showed slower dechlorination rates and DHC migration/growth compared with the other loops. This relatively poor performance was attributed to low pH conditions. Results for the loops inoculated with 3.9 × 10¹¹ and 3.9 × 10¹³ DHC showed similar timeframes for dechlorination, as evaluated at a monitoring well approximately 10 feet downgradient of the DHC injection well. Application of a recently developed one-dimensional bioaugmentation fate and transport screening model provided a reasonable prediction of the data in these two loops. Overall, these results suggest that increasing bioaugmentation dosage does not necessarily result in decreased dechlorination timeframes in the field. The ability to predict results suggests that modeling potentially can serve as an effective tool for determining bioaugmentation dosage and predicting overall remedial timeframes.