Interannual and seasonal variation of the Huanghe (Yellow River) water discharge over the past 50 years: Connections to impacts from ENSO events and dams

The Huanghe, the second largest river in China, is now under great pressure as a water resource. Using datasets of river water discharge, water consumption and regional precipitation for the past 50 years, we elucidate some connections between decreasing water discharges, global El Niño/Southern Oscillation (ENSO) events and anthropogenic impacts in the drainage basin. Global ENSO events, which directly affected the regional precipitation in the river basin, resulted in approximately 51% decrease in river water discharge to the sea. The degree of anthropogenic impacts on river water discharge is now as great as that of natural influences, accelerating the water losses in the hydrological cycle. The large dams and reservoirs regulated the water discharge and reduced the peak flows by storing the water in the flood season and releasing it in the dry season as needed for agricultural irrigation. Thus, as a result, large dams and reservoirs have shifted the seasonal distribution patterns of water discharge and water consumption and finally resulted in rapidly increasing water consumption. Meanwhile, the annual distribution pattern of water consumption also changed under the regulation of dams and reservoirs, indicating that the people living in the river basin consume the water more and more to suit actual agricultural schedule rather than depending upon natural pattern of annual precipitation. The combination of the increasing water consumption facilitated by the dams and reservoirs and the decreasing precipitation closely associated with the global ENSO events over the past half century has resulted in water scarcity in this world-famous river, as well as in a number of subsequent serious results for the river, delta and coastal ocean.     

Prospects for the GLAS Rayleigh laser beacon on the 4.2-m WHT

The scientific exploitation of adaptive optics (AO) with natural guide stars is severely constrained by the limited presence of bright guide stars for wavefront sensing. Use of a laser beam as an alternative means to provide a source for wavefront sensing has the potential of drastically improving the sky coverage for AO. For this reason at the 4.2-m William Herschel Telescope a project was started to develop a Rayleigh laser beacon to work together with the existing NAOMI adaptive optics instrumentation and the OASIS integral field spectrograph. This paper presents the rationale for this development, highlights some of the technical aspects, and gives some expected performance measures.     

kSZ from patchy reionization: The view from the simulations

We present the first calculation of the kinetic Sunyaev–Zel’dovich (kSZ) effect due to the inhomogeneus reionization of the universe based on detailed large-scale radiative transfer simulations of reionization. The resulting sky power spectra peak at ℓ = 2000–8000 with maximum values of [ℓ(ℓ + 1)C_ℓ/(2π)]_max  4–7 × 10 ⁻¹³. The scale roughly corresponds to the typical ionized bubble sizes observed in our simulations, of 5–20 Mpc. The kSZ anisotropy signal from reionization dominates the primary CMB signal above ℓ = 3000. At large-scales the patchy kSZ signal depends only on the source efficiencies. It is higher when sources are more efficient at producing ionizing photons, since such sources produce larger ionized regions, on average, than less efficient sources. The introduction of sub-grid gas clumping in the radiative transfer simulations produce significantly more power at small-scales, but has little effect at large-scales. The patchy reionization kSZ signal is dominated by the post-reionization signal from fully-ionized gas, but the two contributions are of similar order at scales ℓ  3000 − 10⁴, indicating that the kSZ anisotropies from reionization are an important component of the total kSZ signal at these scales.     

Terrestrial age measurements using natural thermoluminescence of a drained zone under the fusion crust of Antarctic ordinary chondrites

Abstract— Miono et al. (1990) and Miono and Nakanishi (1994) have proposed that the build‐up of natural thermoluminescence (TL) in a drained layer directly below the meteorite fusion crust can be used to determine terrestrial ages of meteorites in the 40 to 200 ka range. We have measured the natural TL of the drained layer of 15 meteorites. The data indicate that this technique could be used to determine terrestrial ages of meteorites with ages <200 ka, after which TL equilibrium is reached. Comparison of TL build‐up with terrestrial ages for a suite of Antarctic meteorites suggests that the meteorites have been exposed to temperatures of 0 to 5 °C. The close correspondence between natural TL levels and surface exposure TL growth curves suggest that Allan Hills meteorites with ages <200 ka have spent a significant portion of their terrestrial history exposed on the ice surface, rather than being buried in the ice sheet. The technique is, however, sensitive to thermal history; and, for Antarctic meteorites with terrestrial ages <200 ka, natural TL of the drained zone largely reflects exposure on the ice surface.     

Lunar meteorite Queen Alexandra Range 94281: Glass compositions and other evidence for launch pairing with Yamato 793274

Abstract— Lunar meteorite Queen Alexandra Range 94281 is remarkably similar to Yamato 793274. Pairing in the conventional Earth-entry sense is difficult to reconcile with the 2500 km separation between the find locations for these two samples. Nonetheless, both of these regolith breccias are dominated by very-low-Ti (VLT) mare basalt, the pyroxenes of which feature exsolution lamellae on a remarkably coarse scale (typical lamella width = 0.5–1 μm) by mare standards. The pyroxenes also show similar compositional variations (e.g., Fe# vs. Ti# trends, which confirm parentage from VLT mare basalt). Plots using Al₂O₃ or FeO as a tracer of the highland component indicate indistinguishable internal mare-highland geochemical mixing trends. The same two distinctive glass types dominate the mare glass populations of both breccias. Glass type YQ1 features 0.37–0.63 wt% TiO₂, 10–17 wt% MgO, and 9–11 wt% Al₂O₃. Glass type YQ2 features higher TiO₂ (0.99–1.22 wt%), which is inversely correlated with MgO (12.6–13.8 wt%), and nearly constant (8.8 wt%) Al₂O₃. All of these similarities suggest that Y-793274 and QUE 94281 are a launch pair, which we designate YQ. Most of these similarities also extend to another mare-breccia meteorite, Elephant Moraine 87521. However, the EET 87521 mare basalt is unusually V-poor (～88 μg/g), whereas the YQ mare component contains ～166 μg/g. Queen Alexandra Range 94281 features a variety of textural domains. Discrete patches of dark matrix material appear to represent clods of mature regolith that have been mixed with a coarser, relatively immature material. Interior to a frothy fusion crust are areas of massive glass that probably formed as a splash coating on QUE 94281 when it was still on the Moon. The coarse YQ and EET 87521 pyroxene exsolution features imply relatively slow cooling in either a very shallow sill or an unusually thick (ponded) lava and/or later annealing within a cryptomare. Mare pyroclastic glasses, including the two YQ varieties, are systematically MgO-rich compared to crystalline mare basalts. This disparity may be a consequence of limited survival of graphite—the main fuel for explosive volcanism—during formation of the mare source regions as magma ocean cumulates. Graphite (2.2 g/cm³) survived preferentially in regions that avoided extensive early melting and thus remained MgO-rich. An apparent bimodality in the TiO₂ contents of mare volcanics, especially the pyroclastic glasses, also seems a plausible consequence of petrogenesis by remelting of magma ocean cumulates. Cumulates deposited after the magma ocean evolved to ilmenite saturation had vastly higher TiO₂ contents than cumulates deposited shortly before. The YQ regolith's subequal proportions of mare and highland matter are consistent with derivation from a terrain close to a mare-highland boundary. However, a similar mixture might also develop through vertical mixing in a cryptomare or a region of thin mare coverage. Thus, unfortunately, the YQ bulk composition is not a very useful clue to the identity of the source crater.     

M4–18: the planetary nebula and its WC10 central star

We present a detailed analysis of the planetary nebula M4–18 (G146.7+07.6) and its WC10-type Wolf–Rayet (WR) central star, based on high‐quality optical spectroscopy (WHT/UES, INT/IDS, WIYN/DensPak) and imaging ( HST /WFPC2). From a non-LTE model atmosphere analysis of the stellar spectrum, we derive T _eff=31 kK,     v _∞=160 km s⁻¹ and abundance number ratios of H/He<0.5, C/He=0.60 and O/He=0.10. These parameters are remarkably similar to those of He 2–113 ([WC10]). Assuming an identical stellar mass to that determined by De Marco et al. for He 2–113, we obtain a distance of 6.8 kpc to M4–18 [ E ( B−V )=0.55 mag from nebular and stellar techniques]. This implies that the planetary nebula of M4–18 has a dynamical age of ∼3100 yr, in contrast to ≥270 yr for He 2–113. This is supported by the much higher electron density of the latter. These observations may be reconciled with evolutionary predictions only if [WC]-type stars exhibit a range in stellar masses.
Photoionization modelling of M4–18 is carried out using our stellar WR flux distribution, together with blackbody and Kurucz energy distributions obtained from Zanstra analyses. We conclude that the ionizing energy distribution from the WR model provides the best consistency with the observed nebular properties, although discrepancies remain.     

A 20 cm2 CCD mosaic camera for a dark matter search part I : Mechanics,optics and cryogeny

A 20cm ² CCD mosaic camera has been especially built to search for dark galactic halo objects by the gravitational microlensing effect. The sensitive area is made of 16 edge-buttable CCDs developped by Thomson-CTS, with 23×23 µm ² pixels. The 35 kg camera housing and mechanical equipment is presented. The associated electronics and data acquisition system are described in a separate paper. The camera resides at the focal plane of a 40 cm, f/10, Ferson reflector. The instrument has been in operation since December 1991 at the La Silla Observatory (ESO).