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.     

The shape of the sunspot cycle

The temporal behavior of a sunspot cycle, as described by the International sunspot numbers, can be represented by a simple function with four parameters: starting time, amplitude, rise time, and asymmetry. Of these, the parameter that governs the asymmetry between the rise to maximum and the fall to minimum is found to vary little from cycle to cycle and can be fixed at a single value for all cycles. A close relationship is found between rise time and amplitude which allows for a representation of each cycle by a function containing only two parameters: the starting time and the amplitude. These parameters are determined for the previous 22 sunspot cycles and examined for any predictable behavior. A weak correlation is found between the amplitude of a cycle and the length of the previous cycle. This allows for an estimate of the amplitude accurate to within about 30% right at the start of the cycle. As the cycle progresses, the amplitude can be better determined to within 20% at 30 months and to within 10% at 42 months into the cycle, thereby providing a good prediction both for the timing and size of sunspot maximum and for the behavior of the remaining 7–12 years of the cycle. The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.     

Dissipation of fast magnetoacoustic waves in a cold plasma

The dissipation of ducted, fast magnetoacoustic waves by ion viscosity, electron heat conduction and radiation is re-considered and the results show that these waves are not readily dissipated in the solar corona. It seems unlikely, therefore, that they will play a role in the heating of the solar atmosphere.     

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.     

Evaluation of the snow‐covered area data product from MODIS

The Moderate Resolution Imaging Spectroradiometer (MODIS), flown on board the Terra Earth Observing System (EOS) platform launched in December 1999, produces a snow‐covered area (SCA) product. This product is expected to be of better quality than SCA products based on operational satellites (notably GOES and AVHRR), due both to improved spectral resolution and higher spatial resolution of the MODIS instrument. The gridded MODIS SCA product was compared with the SCA product produced and distributed by the National Weather Service National Operational Hydrologic Remote Sensing Center (NOHRSC) for 46 selected days over the Columbia River basin and 32 days over the Missouri River basin during winter and spring of 2000–01. Snow presence or absence was inferred from ground observations of snow depth at 1330 stations in the Missouri River basin and 762 stations in the Columbia River basin, and was compared with the presence/absence classification for the corresponding pixels in the MODIS and NOHRSC SCA products. On average, the MODIS SCA images classified fewer pixels as cloud than NOHRSC, the effect of which was that 15% more of the Columbia basin area could be classified as to presence–absence of snow, while overall there was a statistically insignificant difference over the Missouri basin. Of the pixels classified as cloud free, MODIS misclassified 4% and 5% fewer overall (for the Columbia and Missouri basins respectively) than did the NOHRSC product. When segregated by vegetation cover, forested areas had the greatest differences in fraction of cloud cover reported by the two SCA products, with MODIS classifying 13% and 17% less of the images as cloud for the Missouri and Columbia basins respectively. These differences are particularly important in the Columbia River basin, 39% of which is forested. The ability of MODIS to classify significantly greater amounts of snow in the presence of cloud in more topographically complex, forested, and snow‐dominated areas of these two basins provides valuable information for hydrologic prediction. Copyright © 2003 John Wiley & Sons, Ltd.     

Wave propagation in a magnetically structured atmosphere

The propagation of waves in a magnetic slab embedded in a magnetic environment is investigated. The possible modes of propagation are examined from the general dispersion relation, both analytically and numerically, for disturbances which are evanescent in the environment. Approximate dispersion relations governing propagation in a slender slab of field are derived both from the general dispersion relation and from an application of the slender flux tube approximation.Several different situations, representative of both photospheric and coronal conditions, are considered. In general, the structures are found to support both fast and slow, body and surface, waves. Under coronal conditions, for two dimensional propagation, disturbances propagate as fast and slow body waves. The fast body waves are analogous to the ducted shear waves of seismology (Love waves).     

Role of nuclear volume in driving equilibrium stable isotope fractionation of mercury, thallium, and other very heavy elements

Equilibrium stable isotope fractionations of mercury and thallium are estimated for molecules, atoms and ions using first-principles vibrational frequency and electronic structure calculations. These calculations suggest that isotopic variation in nuclear volume is the dominant cause of equilibrium fractionation, driving ²⁰⁵Tl/²⁰³Tl and ²⁰²Hg/¹⁹⁸Hg fractionations of up to 3‰ at room temperature. Mass-dependent fractionations are smaller, ca. 0.5-1‰ for the same isotopes. Both fractionation mechanisms tend to enrich the neutron-rich isotopes in oxidized mercury- and thallium-bearing phases (Tl³⁺ and Hg²⁺) relative to reduced phases (Tl⁺ and Hg⁰). Among Hg²⁺-bearing species, inorganic molecules and complexes like HgCl₂, and will have higher ²⁰²Hg/¹⁹⁸Hg than coexisting methylmercury species, suggesting a possible application of Hg-isotope measurements to understanding mercury methylation and increasing methylmercury concentrations at the top of the food chain. Estimated ²⁰⁵Tl/²⁰³Tl fractionation between and is in reasonable agreement with the fractionations previously observed between seawater and Fe-Mn crusts, supporting an equilibrium-like reduction/oxidation fractionation mechanism.More generally, nuclear-volume isotope fractionation will concentrate larger (heavier) nuclei in species where the electron density at the nucleus is small—due to lack of s-electrons (e.g., Hg²⁺—[Xe]4f¹⁴5d¹⁰6s⁰ vs. Hg⁰—[Xe]4f¹⁴5d¹⁰6s²) or enhanced s-electron screening by extra p, d, or f electrons (e.g., Tl⁰—[Xe]4f¹⁴5d¹⁰6s²6p¹ vs. Tl⁺—[Xe]4f¹⁴5d¹⁰6s²6p⁰). Nuclear-volume fractionations become much smaller for lighter elements, declining from ∼1‰/amu for thallium and mercury to ∼0.2‰/amu for ruthenium and ∼0.02‰/amu for sulfur.     

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.     

The Kilo-Degree Survey

The Kilo Degree Survey (KiDS) is a 1500 square degree optical imaging survey with the recently commissioned OmegaCAM wide-field imager on the VLT Survey Telescope (VST). A suite of data products will be delivered to the European Southern Observatory (ESO) and the community by the KiDS survey team. Spread over Europe, the KiDS team uses Astro-WISE as its main tool to collaborate efficiently and pool hardware resources. In Astro-WISE the team shares, calibrates and archives all survey data. The data-centric architectural design realizes a dynamic ‘live archive’ in which new KiDS survey products of improved quality can be shared with the team and eventually the full astronomical community in a flexible and controllable manner.