The Astro-WISE approach to quality control for astronomical data

We present a novel approach to quality control during the processing of astronomical data. Quality control in the Astro-WISE Information System is integral to all aspects of data handing and provides transparent access to quality estimators for all stages of data reduction from the raw image to the final catalog. The implementation of quality control mechanisms relies on the core features in this Astro-WISE Environment (AWE): an object-oriented framework, full data lineage, and both forward and backward chaining. Quality control information can be accessed via the command-line awe-prompt and the web-based Quality-WISE service. The quality control system is described and qualified using archive data from the 8-CCD Wide Field Imager (WFI) instrument (http://www.eso.org/lasilla/instruments/wfi/) on the 2.2-m MPG/ESO telescope at La Silla and (pre-)survey data from the 32-CCD OmegaCAM instrument (http://www.astro-wise.org/~omegacam/) on the VST telescope at Paranal.     

Equipment Decontamination Procedures for Ground Water and Vadose Zone Monitoring Programs: Status and Prospects

A major portion of the work effort and, therefore, the money spent during investigations of ground water and the vadose zone at hazardous waste sites is associated with collecting chemical data. To that end, effective decontamination of reusable drilling equipment, sampling apparatus, and tools is critical to the credibility of chemical data. Samples representative of the site under study are essential.
Several state and federal regulatory agencies have established guidelines for procedures that should be considered when developing decontamination protocols. These agencies were contacted and asked to furnish copies of their decontamination guidelines. The information received was reviewed, and comparisons were made to assess the status of standards of decontamination practices for ground water and vadose zone monitoring programs at hazardous waste sites. Summaries of a variety of decontamination protocols were prepared. From this review, it is apparent that there is a need to standardize, to the extent possible, procedures for the field decontamination of equipment.
Two ASTM Subcommittees, D18.14 on Waste Management and D18.21 on Ground Water and Vadose Zone Monitoring, are currently working on developing standards for decontamination procedures. They, in cooperation with state and federal agencies and other interested technical groups, will develop standards for the field decontamination of equipment used to study ground water and the vadose zone.     

OCO in Earth’s atmosphere

The chemistry and budgets of atmospheric gases are constrained by their bulk stable isotope compositions (e.g., δ¹³C values), which are based on mixing ratios of isotopologues containing one rare isotope (e.g., ¹⁶O¹³C¹⁶O). Atmospheric gases also have isotopologues containing two or more rare isotopes (e.g., ¹⁸O¹³C¹⁶O). These species have unique physical and chemical properties and could help constrain origins of atmospheric gases and expand the scope of stable isotope geochemistry generally. We present the first measurements of the abundance of ¹⁸O¹³C¹⁶O from natural and synthetic sources, discuss the factors influencing its natural distribution and, as an example of its applied use, demonstrate how its abundance constrains the sources of CO₂ in the Los Angeles basin. The concentration of ¹⁸O¹³C¹⁶O in air can be explained as a combination of ca. 1‰ enrichment (relative to the abundance expected if C and O isotopes are randomly distributed among all possible isotopologues) due to enhanced thermodynamic stability of this isotopologue during isotopic exchange with leaf and surface waters, ca. 0.1‰ depletion due to diffusion through leaf stomata, and subtle (ca. 0.05‰) dilution by ¹⁸O¹³C¹⁶O-poor anthropogenic CO₂. Some air samples are slightly (ca. 0.05‰) lower in ¹⁸O¹³C¹⁶O than can be explained by these factors alone. Our results suggest that ¹⁸O¹³C¹⁶O abundances should vary by up to ca. 0.2‰ with latitude and season, and might have measurable sensitivities to stomatal conductances of land plants. We suggest the greatest use of Δ₄₇ measurements will be to “leverage” interpretation of the δ¹⁸O of atmospheric CO₂.     

K-Ar ages of the metamorphic sole of the Semail Ophiolite: implications for ophiolite cooling history

K–Ar ages have been determined on micas and hornblendes in the basal metamorphic sequence and in metamorphic rocks squeezed into the mantle sequence of the Semail Ophiolite. The hornblende ages of 99±0.5 and 102±0.8 Ma and the 90 Ma ages of coexisting micas from the high-grade metamorphic portion of the sequence are interpreted as cooling stages following the peak of metamorphism (T 800–850° C, P 6.5–9 kbar). The new pressure estimates are based on findings of kyanite in garnet-amphibolite and cordierite in quartzitic rocks. These data indicate a cooling rate of 10–30° C/Ma. The oldest mica ages of 95±1 Ma are observed in the lowest-grade greenschists. These also largely represent cooling ages, but might in part also include formation ages. The pattern of the muscovite ages across the metamorphic sole indicates that the cooling front moved from the low-grade metamorphic zone, through the high-grade rocks and into the base of the overlying ophiolite. Radiometric ages of hornblendes (92.3±0.5 and 94.8±0.6 Ma) indicate that the crustal gabbro sequence cooled below 500° C later than the base of the ophiolite sequence. Metamorphism of the sole rocks occurred during subduction of oceanic sediments and volcanic or gabbroic rocks as they progressively came into contact with hotter zones at the base of the overriding plate. The peak of metamorphism must have been contemporaneous with the main magmatism in the Semail Ophiolite. One of the dated muscovites yields an age of 81.3±0.8 Ma, but this is related to discrete deformation zones that were active during late-stage emplacement of the ophiolite.     

Minor planet 1983TB: A dead comet?

IDS spectra of the Apollo asteroid 1983TB were obtained at McDonald Observatory on 2 December 1983 UT. These spectra were examined for cometary-type emission and none were found. The reflectance of 1983TB was found to be similar to an S-type asteroid.     

Effects of projected climate change on the hydrology in the Mono Lake Basin, California

The Californian Mono Lake Basin (MLB) is a fragile ecosystem, for which a 1983 ruling carefully balanced water diversions with ecological needs without the consideration of global climate change. The hydroclimatologic response to the impact of projected climatic changes in the MLB has not been comprehensively assessed and is the focus of this study. Downscaled temperature and precipitation projections from 16 Global Climate Models (GCMs), using two emission scenarios (B1 and A2), were used to drive a calibrated Soil and Water Assessment Tool (SWAT) hydrologic model to assess the effects on streamflow on the two significant inflows to the MLB, Lee Vining and Rush Creeks. For the MLB, the GCM ensemble output suggests significant increases in annual temperature, averaging 2.5 and 4.1 °C for the B1 and A2 emission scenarios, respectively, with concurrent small (1–3 %) decreases in annual precipitation by the end of the century. Annual total evapotranspiration is projected to increase by 10 mm by the end of the century for both emission scenarios. SWAT modeling results suggest a significant hydrologic response in the MLB by the end of the century that includes a) decreases in annual streamflow by 15 % compared to historical conditions b) an advance of the peak snowmelt runoff to 1 month earlier (June to May), c) a decreased (10–15 %) occurrence of ‘wet’ hydrologic years, and d) and more frequent (7–22 %) drought conditions. Ecosystem health and water diversions may be affected by reduced water availability in the MLB by the end of the century.     

Tree-ring reconstructed dry season rainfall in Guatemala

Climate Dynamics - Drought in Guatemala has negative consequences for agriculture and potable water supplies, particularly in regions of the country with highly seasonal rainfall. General...