Simple two-dimensional kinematic framework designed to test warm rain microphysical models

This paper describes a two-dimensional kinematic framework designed to test warm rain microphysical models. The idealized flow field is based on a case study from the Hawaiian Rainband Project (1990). Analyses of radar and aircraft data collected in convective cells embedded in Hawaiian rainbands are included for model validation. A Cloud Condensation Nuclei (CCN) activation spectrum, a condensational growth equation including the CCN chemical composition, collection efficiencies, and terminal velocities of the growing drops, are all provided. A sample set of figures from the test run with bulk microphysical parameterization illustrates the desired format for comparisons between the detailed model results and for validation of the model output with observations. This simple yet realistic test formulation includes vertical and horizontal advection, and can be used to evaluate microphysical model performance without complexities resulting from dynamical–microphysical interactions in dynamic cloud models. Without such interactions, scientists can focus on key physical processes involved in the formation of warm rain. The accurate representation of these processes in detailed models is essential to successfully simulate the observed evolution of warm precipitating clouds.     

FR II radio galaxies with z < 0.3 — I. Properties of jets, cores and hotspots

In previous papers we have discussed high-resolution observations of a large sample of powerful radio galaxies with z  < 0.3. Jets are detected in up to 80 per cent of the sample, and radio cores in nearly all the objects; in addition, we are able to resolve the hotspots in most sources. In this paper we present measurements of the radio properties of these components.   The prominences of the jets detected do not appear to be a function of radio luminosity, providing the clearest evidence yet that the reported low detection rate of jets in radio galaxies has been an artefact of low-sensitivity observations. We find a positive correlation between the total source length and core prominence in the narrow-line radio galaxies. We have found evidence for a relationship between hotspot size and total source size, but few other significant relationships between hotspot properties and those of the jets or lobes. We compare our measurements with those of Bridle et al., based on observations of a sample of quasars, and argue that the results are consistent with a modification of the unified model in which the broad-line radio galaxies are the low-luminosity counterparts of quasars, although the situation is complicated by contamination with low-excitation radio galaxies which appear to have radio properties different from the high-excitation objects. We discuss the classes of empirical model that can be fitted to the data set.     

Particle size distributions of methanesulfonate in the tropical pacific marine boundary layer

Fourteen high-volume cascade impactor samples were collected during a January-February, 1990, research cruise in the tropical Pacific from Panama to 180°. Aqueous extracts of the samples were analyzed for methanesulfonate (MSA), sulfate, and the seasalt tracer ion magnesium. The majority of MSA size distributions showed no pronounced maximum on submicrometer particles, as has been observed elsewhere. Analysis of the data indicated that MSA was distributed essentially uniformly with the effective surface area of particles >0.5 m in radius, which were primarily seasalt. Relatively less MSA was found in smaller particles which were primarily sulfate. These results are consistent with those from theoretical and laboratory experimental studies reported in the literature which suggest that MSA produced from photochemical oxidation of dimethylsulfide condenses on pre-existing particles in strong preference to nucleating into new particles. This implies that MSA may not contribute appreciably to enhancing cloud condensation nucleus populations in the remote tropical marine atmosphere.     

40Ar-39Ar ages and trace element contents of Apollo 14 breccias; an interlaboratory cross-calibration of 40Ar-39Ar standards

Rare gas data are presented from step-wise heatings of lunar breccias 14066 and 14318 and from an interlaboratory cross-calibration of five standards used in ⁴⁰Ar-³⁹Ar dating. Four samples of 14066 all show depressed ⁴⁰¹Ar/³⁹¹Ar ratios at high temperatures, thus making age interpretation uncertain. While different in detail, the Ar release patterns in the four samples yield indistinguishable plateau ages of $\text{3.93 ± 0.03}$ b.y. and > 400°C total ages of $\text{3.87 ± 0.06}$ b.y. Concentrations of K, Ca, Ba, Br, U and I are given for 14318 and 14066. We also present an updating of all of the ⁴⁰Ar-³⁹Ar ages and trace element concentrations previously published by this laboratory.⁴⁰Ar-³⁹Ar dating standards from Menlo Park, Pasadena, Stony Brook, Toronto and Berkeley are calibrated against each other and the internal homogeneity of their ⁴⁰¹Ar/K ratios is tested. The Berkeley standard (from the St. Severin meteorite) has an age of $\text{4.504 ± 0.020}$ b.y. from this intercalibration.⁸⁰Kr from capture of lunar neutrons is detected in 14318. A comparison of the release pattern of the ⁸⁰Kr produced by lunar neutrons with the ^80,82Kr produced by pile neutrons in 14318, indicates that 14318 has lost approximately 35 per cent of the ⁸⁰Kr produced by lunar neutrons.     

Sergej Zilitinkevich (13.4.1936–15.2.2021)

Boundary-Layer Meteorology -     

Lithospheric mantle beneath the south-eastern Siberian craton: petrology of peridotite xenoliths in basalts from the Tokinsky Stanovik

We provide petrographic, major and trace element data for over 30 spinel peridotite xenoliths from the Tokinsky Stanovik (Tok) volcanic field on the Aldan shield to characterize the lithospheric mantle beneath the south-eastern margin of the Siberian craton, which formed in the Mesoproterozoic. High equilibration temperatures (870–1,010°C) of the xenoliths and the absence of garnet-bearing peridotites indicate a much thinner lithosphere than in the central craton. Most common among the xenoliths are clinopyroxene-poor lherzolites and harzburgites with Al₂O₃ and CaO contents nearly as low as in refractory xenoliths from kimberlite pipes (Mir, Udachnaya) in the central and northern Siberian craton. By contrast, the Tok peridotites have higher FeO, lower Mg-numbers and lower modal orthopyroxene and are apparently formed by shallow partial melting (3 GPa). Nearly all Tok xenoliths yield petrographic and chemical evidence for metasomatism: accessory phlogopite, amphibole, phosphates, feldspar and Ti-rich oxides, very high Na₂O (2–3.1%) in clinopyroxene, LREE enrichments in whole-rocks.Electronic Supplementary Material Supplementary material is available for this article at     

The Role of the Kink Instability of a Long-Lived Active Region AR 9604

We have traced the long-term evolution of a non-Hale active region composed of NOAA 9604–9632–9672–9704–9738, which displayed strong transient activity with associated geomagnetic effects from September to December, 2001. By studying the development of spot-group and line-of-sight magnetic field together with the evolution of H_α filaments, the EUV and X-ray corona (TRACE 171 Å, Yohkoh/SXT), we have found that the magnetic structure of the active region exhibited a continuous clockwise rotation throughout its entire life. Vector magnetic data obtained from Huairou Solar Observing Station (HSOS) and full-disk line-of-sight magnetograms from SOHO/MDI allowed the determination of the best-fit force-free parameter (proxy of twist), α_best, and the systematic tilt angle (proxy of writhe) which were both found to take positive values. Soft X-ray coronal loops from Yohkoh/SXT displayed a pronounced forward-sigmoid structure in period of NOAA 9704. These observations imply that the magnetic flux tube (loops) with the same handedness (right) of the writhe and the twist rotated clockwise in the solar atmosphere for a long time. We argue that the continuous clockwise rotation of the long-lived active region may be a manifestation that a highly right-hand twisted and kinked flux tube was emerging through the photosphere and chromosphere into the corona.