A quantitative analysis of the properties of several Mt Ruapehu, New Zealand, ash plumes has been performed using multispectral satellite data from the AVHRR-2 and ATSR-2 instruments. The analysis includes: identification of the plume from background clouds using the 'reverse' absorption effect in the thermal channels; modelling and retrieval of particle sizes; determination of the plume height from cloud shadows, stereoscopy and meteorological data; and estimates of the mass of fine particles (radii less than 10 pm). A new spectral technique for identifying opaque, silica-rich ash clouds is demonstrated by utilizing the near-infrared (1.6 pm) and visible (0.67 pm) channels of the ATSR-2, and the optical properties of a simple volcanic cloud are presented for use in radiative transfer studies. It is found that the Ruapehu eruption cloud contained silica-rich ash particles with radii generally less than a few micrometres. The distribution of fine particles is monomodal with a dominant mode peak of about 3 p m radius. Mass loadings of fine particles are found to be in the range = I to ~7 mg m-3, and are consistent with estimates of mass loadings of volcanic clouds from eruptions of other volcanoes. The height of the plume top, derived from radiosonde data and plume-top temperatures in the opaque regions, was found to be between 7.5 and 8.5 km, while the plume thickness was estimated to be between 1.5 and 3 km. Cloud height derived from ATSR-2 stereoscopy on a different plume gave heights in the range 5 to 8 km.The results of this study provide important information on the optical properties of nascent volcanic eruption plumes. This information may prove useful in determining the potential effects of volcanic clouds on local climate, and in assessing any hazard to aviation. t The time taken for ash particles to fall from 20 to 5 km can be up to a month for spherical particles with radii x.5 pm, but several times longer for some other shapes (Wilson and Huang 1979).* Our analysis will show that this height estimate is in error and that the plume height was certainly no greater than 10 km.

A 6 × 6 diallel cross was conducted in spring-planted oilseed rape (Brassica napus L.) in 1983 at Elora and Dundalk, Ontario. The F1 hybrids exhibited positive heterosis for seed yield, of up to 72%, over the higher-yielding parent in the hybrid crosses. Heterosis for 1000 seed weight, percent oil, plant height, and lodging resistance was nonsignificant; negative heterosis for percent protein was observed with some hybrids. Generally, the hybrids were intermediate to the parents in flowering date and physiological maturity. Specific combining ability was more important than general combining ability for seed yield, percent oil, percent protein, plant height (Dundalk), and lodging resistance (Elora); specific combining ability was as important as general combining ability for 1000 seed weight, physiological maturity, plant height (Elora), and lodging resistance (Dundalk). The cultivars 'Topas' and 'Regent' were the best general combiners for seed yield. The best specific combinations for seed yield heterosis, 'Westar' × 'Hanna', 'Regent' × 'Liné', and 'Regent' × 'D-1', exhibited average high-parent heterosis values of 50, 38, and 30%, respectively. The results demonstrated that considerable potential exists for producing high-yielding single-cross hybrids of oilseed rape. Commercial exploitation of this heterosis will depend on the successful development of suitable pollination control mechanisms.Key words: Brassica napus, oilseed rape, F1 hybrid, heterosis, combining ability.

We compare measurements of polar cap ionospheric plasma flow over Resolute Bay, Canada, made by a digital ionosonde using the Doppler drift technique with simultaneous measurements at the same location made by the first operational pair of SuperDARN HF radars. During the 3‐hour comparison interval the flow varied widely in direction and from 100 to 600 m/s in speed. The two measurement techniques show very good agreement for both the speed and direction of flow for nearly all of the samples in the interval. The difference between the velocities determined by the two techniques has a scatter of about ±35° in direction and ±30% in speed, with no systematic difference above the level of the scatter. The few samples which strongly disagreed were usually associated with strong spatial structure in the flow pattern measured by SuperDARN in the vicinity of the comparison point. The drift speed measured by the ionosonde was independently verified by observing the time taken for polar cap F layer ionization patches to drift between ionosondes sited at Eureka and Resolute Bay. These results confirm that the speed and direction of the polar cap ionospheric convection can be reliably monitored by the ionosonde Doppler drift technique.

At any site, the bankability of a projected solar power plant largely depends on the accuracy and general quality of the solar radiation data generated during the solar resource assessment phase. The term “site adaptation” has recently started to be used in the framework of solar energy projects to refer to the improvement that can be achieved in satellite-derived solar irradiance and model data when short-term local ground measurements are used to correct systematic errors and bias in the original dataset. This contribution presents a preliminary survey of different possible techniques that can improve long-term satellite-derived and model-derived solar radiation data through the use of short-term on-site ground measurements. The possible approaches that are reported here may be applied in different ways, depending on the origin and characteristics of the uncertainties in the modeled data. This work, which is the first step of a forthcoming in-depth assessment of methodologies for site adaptation, has been done within the framework of the International Energy Agency Solar Heating and Cooling Programme Task 46 “Solar Resource Assessment and Forecasting”

Bioassays were developed in Zimbabwe to measure pyrethroid in cattle dung. These and chemical assays then estimated concentrations in dung from treated oxen and elucidated risks to dung fauna. Laboratory bioassays with adult beetles (Histeridae and Scarabaeinae, including Copris, Digitonthophagus, Onitis and Sisyphus spp.) and muscoid larvae (Musca lusoria Wiedemann) indicated that the LC50 of pyrethroids, as ppm in the wet weight, averaged 0.04 for deltamethrin pour-on, 0.25 for deltamethrin dip, 0.22 for alphacypermthrin pour-on, 0.10 for cyfluthrin pour-on, 0.23 for cypermethrin dip and 0.63 for flumethrin dip. Field bioassays involved artificial dung pats of 800 g, deployed in woodland and inspected after 24 h to record insects dead and alive. Beetles were most abundant in the wet season. Muscoid larvae were less seasonal. The LC50 of insecticides in the field confirmed laboratory indications. Adult Diptera (muscoids and Sgifidae) were not repelled or killed until the deltamethrin concentration reached 10 ppm. Pat dispersal by dung fauna and termites (Microtermes spp.) was halved by deltamethrin at 0.1-1 ppm. Scavenging of dead beetles by ants was greatest with small beetles (< 15 mm long) uncontaminated with insecticide. Dips and pour-ons of deltamethrin on cattle gave residues of about 0.01-0.1 ppm in dung produced in the fortnight after application. About 1.6% of the deltamethrin applied was transferred to dung. Deltamethrin and alphacypermethrin in dung showed no detectable degradation in 64 days. Contamination levels threaten populations of slow-breeding beetles.