Upper stratosphere negative ion composition measurements and inferred trace gas abundances

In situ composition measurements of atmospheric negative ions were made at 40.8 km altitude using a balloon-borne mass spectrometer with large mass range and improved mass resolution. The data obtained show marked differences compared to previous data obtained mostly around or below 33 km.It appears that these differences are mostly due to a higher atmospheric temperature, a lower nitric acid vapour abundance and a larger HSO₃-vapour abundance prevailing at the higher altitude.A particularly striking feature is the relatively large fractional abundance of HSO₃-containing cluster ions.Another interesting result is that nitric acid vapour abundances can be inferred from the negative ion composition data with better accuracy than is possible for lower altitudes. The reason being that collisional ion dissociation occurring during ion sampling is less disturbing.The inferred nitric acid vapour abundance for 40.8 km altitude is consistent with current 2-dimensional model calculations.     

Be andCl depth profiles in an Apollo 15 drill core

Cosmic-ray-produced¹⁰Be (t_1/2 = 1.6 × 10⁶ years) and³⁶Cl (t_1/2 = 3.0 × 10⁵ years) have been measured in the Apollo 15 long core for study of galactic cosmic ray production profiles using tandem accelerator mass spectrometry. From these experiments, the half-attenuation length for¹⁰Be production and³⁶Cl production were calculated to be 120 g/cm² and 132 g/cm² (150–400 g/cm² region). The measured half-attenuation length for¹⁰Be is slightly longer than that predicted by the Reedy-Arnold theoretical model. The flatter and somewhat deeper maximum seen in the³⁶Cl profile compared to the¹⁰Be,²⁶Al and⁵³Mn profiles can be explained by production from secondary thermal neutrons on³⁵Cl.     

Mechanical response of the south flank of kilauea volcano, hawaii, to intrusive events along the rift systems

Increased earthquake activity and compression of the south flank of Kilauea volcano, Hawaii, have been recognized by previous investigators to accompany rift intrusions. We further detail the temporal and spatial changes in earthquake rates and ground strain along the south flank induced by six major rift intrusions which occurred between December 1971 and January 1981. The seismic response of the south flank to individual rift intrusions is immediate; the increased rate of earthquake activity lasts from 1 to 4 weeks. Horizontal strain measurements indicate that compression of the south flank usually accompanies rift intrusions and eruptions. Emplacement of an intrusion at a depth greater than about 4 km, such as the June 1982 southwest rift intrusion, however, results in a slight extension of the subaerial portion of the south flank.Horizontal strain measurements along the south flank are used to locate the January 1983 east-rift intrusion, which resulted in eruptive activity. The intrusion is modeled as a vertical rectangular sheet with constant displacement perpendicular to the plane of the sheet. This model suggests that the intrusive body that compressed the south flank in January 1983 extended from the surface to about 2.4 km depth, and was aligned along a strike of N66°E. The intrusion is approximately 11 km in length, extended beyond the January 1983 eruptive fissures, which are 8 km in length and is contained within the 14-km-long region of shallow rift earthquakes.     

Reconstruction of the last deglaciation: deconvolved records of δ18O profiles,micropaleontological variations and accelerator mass spectrometric14C dating

Bioturbation acts as a low-pass filter in displacing and reducing the amplitudes of stratigraphic signals. This often leads to a loss of high-frequency events in the stratigraphic record. In addition, when considering an isotopic signal ¹⁸O,¹⁴C measured in stratigraphic carriers, such as foraminifera, bioturbation and carrier abundance changes can create artifacts which may be falsely interpreted as leads or lags in the paleoclimatic record.We presenthere a model in which bioturbationis treated as a time-invariant filter whose impulse response function (IRF) is like that of a first-order system. The method involves first deconvoluting the abundance curves of the carriers and then the isotopic signals using the restored carrier abundances. This analysis was initially used to artificially generate ideal curves, with the aim of qualitatively modelling the effects of bioturbation. Following this, deconvolved curves were obtained using data from the core CH73-139C using ¹⁸O, A. M. S. C-14 ages, and abundances of two planktonic foraminifera:G. bulloides andN. pachyderma left-coiling. A comparison of the data with the unmixed curves enables separation of the bioturbation artifacts and the construction of a common deglaciation curve based on the restored signals.Importantly, the model emphasizes some severe limitations of mathematical analysis of stratigraphic signals.     

Le système hydrothermal actuel de Los Humeros (Mexique): Etat du système SO −− 4 —SH2 à 300°C,origine du soufre et phénomènes d'oxydation associés à l'ébullition du fluide ascendant

In the geothermal system of Los Humeros, hydrothermal fluids are low in sulfur (7.7 mM/kg) and are slightly alkaline (pH of ca. 8.5) at depth. Nevertheless, the aqueous sulfate-sulfide species are in isotopic and chemical equilibrium. The “freezing” of these equilibria at 290 °C is tentatively related to boiling of water at this temperature. In the LH1 borehole δ³⁴S values for pyrite (ca. 0‰) and present aqueous SH₂ (ca. ?12‰) are very different. Measured δ³⁴S value of the bulk aqueous sulfur is close to ?11‰ These data suggest a possible magmatic origin of pyrite (ca. 0‰) and, in contrast, a sedimentary source for the present hydrothermal sulfur. The CO₂/CH₄ molar ratio of 58 determined in the fluid from this well is much lower than the ratio calculated for 300° and 350 °C. This divergence is eliminated when the equilibrium constant is reestimated (log K_G=?7.9 at 300 °C). Based on fluid inclusion study the boiling of hydrothermal fluid before the geothermal area was opened by drilling is proven in neoformed minerals sampled at different levels of the volcanic sequence. In this way, the pervasive oxidation of the primary reduced paragenesis (pyrite + pyrrhotite + magnetite) can be explained. The boiling of the ascending water does induce a H₂ loss from the liquid and creates more oxidizing conditions in the ascending liquid. Moreover, the continuous vaporization of liquid water induces its gradual cooling and increases the ascension speed. Furthermore, a persistence of chemical equilibrium between primary paragenesis and the hydrothermal fluid at different levels would require a very fast and unrealistic adjustment of the fO₂-fH₂ parameters to the local equilibrium conditions. This expected disequilibrium induces the afore mentioned oxidation processes under steady-state conditions.     

Infrared visibility prediction by statistical methods

This study attempts to find statistical methods of predicting infrared visibility (IRV), as calculated from hourly meteorological observations from a North Atlantic weather ship. Simple and multiple regressions expressing IRV as a function of its component weather variables, and exponential data transformations, for time lags of 1 to 24 hours, gaveR ² values from 0.68 (1-hour lag) to 0.09 (24-hour lag). These have limited predictive power for lags up to 6 hours, almost none for longer lags. Two-category discriminant analysis, using class breaks at 2 km or 10 km is of little use, due to uneven data distribution.Possibly more promising would be an application of Machine Output Statistics (MOS), used routinely for temperature forecasts, to this problem.     

Effects of size and temperature on mud crab,Panopeus herbstii,predation on hard clams,Mercenaria mercenaria

Predation byPanopeus herbstii onMercenaria mercenaria was significantly affected by temperature, and the size of predators and prey items. LargerP. herbstii opened more clams and preyed more successfully on larger clams than did smaller crabs. Increase in seed clam size and decrease in water temperature significantly reduced predation. Clam size appeared to be more important than crab satiation in reducing predation rate. Planting larger seed clams in cooler months should help to improve clam survival by reducing the impact ofP. herbstii in culture operations.     

Intercomparison of Methods for the Simultaneous Estimation of Zero-Plane Displacement and Aerodynamic Roughness Length from Single-Level Eddy-Covariance Data

We applied three approaches to estimate the zero-plane displacement $d$ through the aerodynamic measurement height $z$ (with $z = z_{m}- d$ and $z_{m}$ being the measurement height above the surface), and the aerodynamic roughness length $z_{0}$ , from single-level eddy covariance data. Two approaches (one iterative and one regression-based) were based on the universal function in the logarithmic wind profile and yielded an inherently simultaneous estimation of both $d$ and $z_{0}$ . The third approach was based on flux–variance similarity, where estimation of $d$ and consecutive estimation of $z_{0}$ are independent steps. Each approach was further divided into two methods differing either with respect to the solution technique (profile approaches) or with respect to the variable (variance of vertical wind and temperature, respectively). All methods were applied to measurements above a large, growing wheat field where a uniform canopy height and its frequent monitoring provided plausibility limits for the resulting estimates of time-variant $d$ and $z_{0}$ . After applying, for each approach, a specific data filtering that accounted for the range of conditions (e.g. stability) for which it is valid, five of the six methods were able to describe the temporal changes of roughness parameters associated with crop growth and harvest, and four of them agreed on $d$ to within 0.3 m most of the time. Application of the same methods to measurements with a more heterogeneous footprint consisting of fully-grown sugarbeet and a varying contribution of adjacent harvested fields exhibited a plausible dependence of the roughness parameters on the sugarbeet fraction. It also revealed that the methods producing the largest outliers can differ between site conditions and stability. We therefore conclude that when determining $d$ for canopies with unknown properties from single-level measurements, as is increasingly done, it is important to compare the results of a number of methods rather than rely on a single one. An ensemble average or median of the results, possibly after elimination of methods that produce outliers, can help to yield more robust estimates. The estimates of $z_{0}$ were almost exclusively physically plausible, although $d$ was considered unknown and estimated simultaneously with the methods and results described above.