The distribution of carbon monoxide in the lower atmosphere of Venus

We have obtained spatially resolved near-infrared spectroscopy of the Venus nightside on 15 nights over three observing seasons. We use the depth of the CO absorption band at 2.3 μm to map the two-dimensional distribution of CO across both hemispheres. Radiative transfer models are used to relate the measured CO band depth to the volume mixing ratio of CO. The results confirm previous investigations in showing a general trend of increased CO abundances at around 60° latitude north and south as compared with the equatorial regions. Observations taken over a few nights generally show very similar CO distributions, but significant changes are apparent over longer periods. In past studies it has been assumed that the CO latitudinal variation occurs near 35 km altitude, at which K-band sensitivity to CO is greatest. By modeling the detailed spectrum of the excess CO at high latitudes we show that it occurs at altitudes around 45 km, much higher than has previously been assumed, and that there cannot be significant contribution from levels of 36 km or lower. We suggest that this is most likely due to downwelling of CO-rich gas from the upper atmosphere at these latitudes, with the CO being removed by around 40 km through chemical processes such as the reaction with SO₃.     

The characteristics of rain electricity in Nigeria. I — Magnitudes and variations

The characteristics of rain and point charges based on routine measurements extending over four rainy seasons are presented. An average rain current density of (1.0±0.1)×10^–10 A m^–2 and charge per unit volume of rain water of (0.43±0.02)×10^–4 C m^–3 for the locality are obtained, which are compared with data obtained elsewhere by other workers. The point-discharge current measurements lead to a revised estimate of (0.86±0.08)×10^–9 A m^–2 for the average point discharge current below storm clouds.     

Circulation anomalies in the atmospheric centers of action during the Eastern Pacific and Central Pacific El Niño

Based on the statistical analysis the teleconnections between circulation anomalies in the atmospheric centers of action and sea surface temperature anomalies are revealed for two types of El Niño. It is demonstrated that for the Eastern Pacific El Niño stronger teleconnections are registered in the Northern Hemisphere whereas the response to the Central Pacific El Niño is much stronger in the Southern Hemisphere. The Central Pacific El Niño is characterized by the more rapid signal propagation from the tropical zone to distant regions. In some cases the pattern of interaction with the atmospheric circulation considerably differs for two types of El Niño that defines differences in the fields of weather anomalies.     

Reflections on the history of research on large wood in rivers

Dynamics and functions of large wood have become integral considerations in the science and management of river systems. Study of large wood in rivers took place as monitoring of fish response to wooden structures placed in rivers in the central United States in the early 20th century, but did not begin in earnest until the 1970s. Research has increased in intensity and thematic scope ever since. A wide range of factors has prompted these research efforts, including basic understanding of stream systems, protection and restoration of aquatic ecosystems, and environmental hazards in mountain environments. Research and management have adopted perspectives from ecology, geomorphology, and engineering, using observational, experimental, and modelling approaches. Important advances have been made where practical information needs converge with institutional and science leadership capacities to undertake multi-pronged research programmes. Case studies include ecosystem research to inform regulations for forest management; storage and transport of large wood as a component in global carbon dynamics; and the role of wood transport in environmental hazards in mountain regions, including areas affected by severe landscape disturbances, such as volcanic eruptions. As the field of research has advanced, influences of large wood on river structures and processes have been merged with understanding of streamflow and sediment regimes, so river form and function are now viewed as involving the tripartite system of water, sediment, and wood. A growing community of researchers and river managers is extending understanding of large wood in rivers to climatic, forest, landform, and social contexts not previously investigated. © 2020 John Wiley & Sons, Ltd.     

Vertical circulation in the tropical atmosphere during extreme El Niño-Southern Oscillation events

Scenarios for the development of large-scale vertical circulation anomalies during warm and cold phases of El Niño-Southern Oscillation are generalized based on the NCEP/NCAR reanalysis data for 1958-1998. Composite models of the cells of vertical circulation in the monsoon and trade-wind regions of the tropical Pacific are obtained for the first time for El Niño and La Niña separately. An unprecedented shift of the ascending branch of the zonal Walker circulation from the “maritime continent” of Indonesia to the east, to the central and eastern Pacific, was observed during the warm phase over the tropical Pacific; this shift was accompanied by an abrupt increase in the tropical cyclogenesis activity in the southern Pacific zone of convergence. On the contrary, during the cold phase, the ascending motions in the region of the summer Australian monsoon are subject to abrupt intensification. The reconstruction of the vertical meridional circulation during the warm phase manifested itself in the almost complete disappearance of the Hadley classic circulation over the central Pacific, characteristic of the trade-wind intertropical convergence zone (ITCZ), and in its replacement by the latitudinal monsoon circulation typical of the ITCZ over the Indian Ocean. During a cold phase, the Hadley circulation is both restored and intensified.     

Formation of the Bencubbin polymict meteoritic breccia

The Bencubbin meteorite is a polymict breccia consisting of a host fraction of ~60% metal and ~40% ferromagnesian silicates and a selection of carbonaceous, ordinary and ‘enstatite’ chondritic clasts. Concentrations of 27 elements were determined by neutron activation in replicate samples of the host silicates and the ordinary and carbonaceous chondritic clasts; 12 elements were determined in the host metal. Compositional data for the ordinary chondrite clast indicate a classification of LL4 ± 1. Refractory element data for the carbonaceous chondrite clast indicate that it belongs to the CI-CM-CO clan; its volatile element abundances are intermediate between those of CM and CO chondrites. Abundances of nonvolatile elements in the silicate host are similar to those in the carbonaceous chondrite clast and in CM chondrites; the rare earths are unfractionated. We conclude that it is not achondritic as previously designated, but chondritic and that it is probably related to the CI-CM-CO clan; its volatile abundances are lower than those in CO chondrites. Oxygen isotope data are consistent with these classifications. Host metal in Bencubbin and in the closely related Weatherford meteorite has low abundances of moderately volatile siderophiles; among iron meteorite groups its nearest relative is group IIIF.We suggest that Bencubbin and Weatherford formed as a result of an impact event on a carbonaceous chondrite regolith. The impact generated an ‘instant magma’ that trapped and surrounded regolithic clasts to form the polymict breccia. The parent of this ‘magma’ was probably the regolith itself, perhaps mainly consisting of the so-called ‘enstatite’ chondrite materials. Accretion of such a variety of materials to a small parent body was probably only possible in the asteroid belt.     

A shipborne magnetic survey in Hudson Bay

A marine magnetic total-field survey of Hudson Bay was conducted from 1975 to 1978. Approximately 62 000 line-km of data, or 35 000 five-minute averages, were acquired. The data were corrected for secular variation by means of a polynomial in latitude, longitude, and time, first fitted to annual mean differences from nine observatories and then integrated over time. The data were corrected for diurnal and transient variations by means of a linear interpolation, over geomagnetic latitude, of running hourly mean values from two neighbouring magnetic stations (numbering seven in all). Crossover differences are analysed in terms of a mixture of normal distributions resulting from the intermittent transient variations, and indicate the effectiveness of the corrections. The variance of the data is reduced, as a result of the corrections, by 87% during quiet periods and by 53% during disturbed periods, the weighted variance being reduced by 66%. Navigational accuracy is estimated, from a novel method utilizing crossover differences and field gradients, to be approximately 300 m. Anomalies are presented in profile form, and discussed briefly.Contribution from the Earth Physics Branch No. 973.     

The flux of secondary anti-deuterons and antihelium produced in the interstellar medium

Several measurements have been performed to find antiprotons in the primary cosmic radiation. Because it is difficult to get completely separated secondary produced antiprotons primary ones, calculations based on accelerator results have been performed for the flux of secondary produced antideuterons and antihelium.     

An Intercomparison of NO2 and OClO Measurements at Arrival Heights, Antarctica during Austral Spring 1996

For several years NO2 and OClO, two species important to understanding ozone destruction in the Antarctic stratosphere, have been measured at Arrival Heights, Antarctica by two groups: New Zealand's National Institute of Water and Atmospheric Research (NIWA) and the NOAA Aeronomy Laboratory in Boulder, Colorado. Using data independently collected by these two groups during the Austral spring of 1996, it is shown that the two data sets are in extremely close agreement. Besides offering validation of the instrumentation and analysis techniques of both groups, this result provides confidence in the more complete history of these species gained by combining the two data sets.