8,632 research outputs found
Rediscovery of Ooline, Cadellia pentastylis, near Gunnedah : notes on the habitat and ecology of this dry rainforest tree
Cadellia pentastylis F.Muell., (family Surianaceae), a dry rainforest tree with a conservation listing of Vulnerable at state and national levels, was first collected from the Gunnedah area by the botanical collector J.L. Boorman in 1907. We report the first record of Cadellia pentastylis from the Gunnedah area (30°58’49’’S, 150°15’15’’E) since 1907, and provide details of the community and habitat where it occurs, on the lower slopes of Black Jack Mountain. Although this population is one of the smallest in New South Wales, it is significant as it is at its southern distributional limit, and is found adjacent to semi-evergreen vine thicket, another type of dry rainforest, on the same hillslope. We list the New South Wales occurrences of this species and discuss aspects of its flowering phenology
Lidar remote sensing from space: NASA's plans in the Earth sciences
A multidisciplinary study of the Earth System to provide a better understanding of the complex interrelated processes involved in the system, the Earth Observing System (EOS), is being developed. Capabilities of the Space Station, both the polar orbiting platform and the lower inclination platforms, will be used to accommodate a number of large active and/or passive sensors. Two lidar instruments being considered as part of the Eos payload are the Lidar Atmospheric Sounder and Altimeter (LASA) and the Laser Atmospheric Wind Sounder (LAWS). The LASA instrument is separable into two portions: the atmospheric sounder component and the retroranging component. The LASA atmospheric sounder will sample the spatial distribution of several atmospheric parameters. The retroranging component will be used to determine the precise three-dimensional position of specifically placed retro-reflectors and to sense how these retro-reflectors change position over monthly to yearly time periods. The LAWS utilizes a lidar system capable of measuring the Doppler shift in the backscattered intensity to determine the wind velocity profile
Localised HI 21-cm absorption towards a double-lobed z=0.24 radio galaxy
We present the results of a mini-survey for associated HI 21-cm absorption at
z < 0.42 with the Giant Metrewave Radio Telescope. Our targets are radio
galaxies, selected on the basis that the 1216 Angstrom luminosities are below
10^23 W/Hz, above which there has never been a detection of 21-cm absorption.
Of the three sources for which we obtained good data, two are unclassified
active galactic nuclei (AGN) and one is type-2. Being a non-detection, the
type-2 object is consistent with our previous result that 21-cm absorption in
radio sources is not dictated by unified schemes of AGN. In the case of the
detection, the absorption only occurs towards one of the two resolved radio
lobes in PKS 1649-062. If the absorption is due to an another intervening
galaxy, or cool HI gas in the intergalactic medium, covering only the
south-west lobe, then, being at the same redshift, this is likely to be
gravitationally bound to the optical object identified as PKS 1649-062. If the
absorption is due to an inclined disk centred between the lobes, intervening
the SW lobe while being located behind the NE lobe, by assuming that it covers
the emission peak at 150 kpc from the nucleus, we estimate a dynamical mass of
~3 x 10^12 solar masses for the disk.Comment: 5 pages accepted by MNRAS Letter
Biomass in the upwelling areas along the northwest coast of Africa as viewed with ERTS-1
Light penetration in water is affected by plankton, algae, and dissolved and suspended matter. As a consequence, the composition of backscattered light from below the air-sea interface is determined by the nature of the constituents in the water column. In contrast to the absorption spectrum of chemically pure chlorophyll in solution, algae suspensions absorb and scatter light more uniformly throughout the visible part of the electromagnetic spectrum. Because of their spectral absorption and scattering properties plankton concentration can be estimated by measuring the spectral backscattered radiance over water. Experiments using this approach were performed in upwelling regions along the northwest coast of Africa
Development of LANDSAT Derived Forest Cover Information for Integration into Adirondack Park GIS
Based upon observed changes in timber harvest practices partially attributable to forest biomass removable for energy supply purposes, the Adirondack Park Agency began in 1979 a multi-year project to implement a digital geographic information system (GIS). An initial developmental task was an inventory of forest cover information and analysis of forest resource change and availability. While developing the GIS, a pilot project was undertaken to evaluate the usefulness of LANDSAT derived land cover information for this purpose, and to explore the integration of LANDSAT data into the GIS. The prototype LANDSAT analysis project involved: (1) the use of both recent and historic data to derive land cover information for two dates; and (2) comparison of land cover over time to determine quantitative and geographic changes. The "recent data," 1978 full foliage data over portions of four LANDSAT scenes, was classified, using ground truth derived training samples in various forested and non-forested categories. Forested categories include the following: northern hardwoods, pine, spruce-fir, and pine plantation, while nonforested categories include wet-conifer, pasture, grassland, urban, exposed soil, agriculture, and water
Albedo climatology analysis and the determination of fractional cloud cover
Monthly and zonally averaged surface cover climatology data are presented which are used to construct monthly and zonally averaged surface albedos. The albedo transformations are then applied to the surface albedos, using solar zenith angles characteristic of the Nimbus 6 satellite local sampling times, to obtain albedos at the top of clear and totally cloud covered atmospheres. These albedos are then combined with measured albedo data to solve for the monthly and zonally averaged fractional cloud cover. The measured albedo data were obtained from the wide field of view channels of the Nimbus 6 Earth Radiation Budget experiment, and consequently the fractional cloud cover results are representative of the local sampling times. These fractional cloud cover results are compared with recent studies. The cloud cover results not only show peaks near the intertropical convergence zone, but the monthly migration of the position of these peaks follows general predictions of atmospheric circulation studies
The application of satellite data in the determination of ocean temperatures and cloud characteristics and statistics
The author has identified the following significant results. The major shortcoming of the data was the loss of the infrared radiances from the S191 spectrometer. The cloud thermodynamic phase determination procedure was derived and tested with the data collected by the S192 multispectral scanner. Results of the test indicate a large fraction of the data could be classified thermodynamically. An added bonus was the inclusion of snow in the classification approach. The conclusion to be drawn from this portion of the effort is that in most cases considered ice clouds, liquid water droplet clouds, and snow fields can be spectroscopically separated to a high degree of accuracy
The effects of ground hydrology on climate sensitivity to solar constant variations
The effects of two different evaporation parameterizations on the climate sensitivity to solar constant variations are investigated by using a zonally averaged climate model. The model is based on a two-level quasi-geostrophic zonally averaged annual mean model. One of the evaporation parameterizations tested is a nonlinear formulation with the Bowen ratio determined by the predicted vertical temperature and humidity gradients near the earth's surface. The other is the linear formulation with the Bowen ratio essentially determined by the prescribed linear coefficient
Probing the cool ISM in galaxies via 21cm HI absorption
Recent targeted studies of associated HI absorption in radio galaxies are
starting to map out the location, and potential cosmological evolution, of the
cold gas in the host galaxies of Active Galactic Nuclei (AGN). The observed 21
cm absorption profiles often show two distinct spectral-line components:
narrow, deep lines arising from cold gas in the extended disc of the galaxy,
and broad, shallow lines from cold gas close to the AGN (e.g. Morganti et al.
2011). Here, we present results from a targeted search for associated HI
absorption in the youngest and most recently-triggered radio AGN in the local
universe (Allison et al. 2012b). So far, by using the recently commissioned
Australia Telescope Compact Array Broadband Backend (CABB; Wilson et al. 2011),
we have detected two new absorbers and one previously-known system. While two
of these show both a broad, shallow component and a narrow, deep component (see
Fig. 1), one of the new detections has only a single broad, shallow component.
Interestingly, the host galaxies of the first two detections are classified as
gas-rich spirals, while the latter is an early-type galaxy. These detections
were obtained using a spectral-line finding method, based on Bayesian
inference, developed for future large-scale absorption surveys (Allison et al.
2012a).Comment: 1 page, 1 figure, published in Proceedings of IAU Symposium No. 29
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