Abstract. Radar echoes from ranges less than 500 km are routinely observed by the Super Dual Auroral Radar Network (SuperDARN) on most days. Many of these echoes have properties which are markedly different from what one would expect from E or F region irregularities. We show that these unusual short-range HF echoes are due to scattering off meteor trails. This explains why, among other things, the Doppler shift from the short-range echoes taken from the SuperDARN Saskatoon antenna are consistent with the mesospheric winds observed by the Saskatoon MF radar. This means that the SuperDARN radars can be used to study neutral winds at meteor heights, a result which is especially interesting since it opens up the capability for a global coverage of mesospheric winds using the worldwide distribution of SuperDARN radars.
A 937‐horizon data set composed of site characteristics, morphology, and laboratory characterization data for soils of Ohio was used to develop soil bulk density (Db) prediction models. We tested the hypothesis that using a combination of continuous variables (laboratory data) and nominal variables (site/state factor and morphological class descriptors) would enable the development of improved Pedo‐Transfer Functions (PTFs) for Db Three primary models were developed. The Lab Model, composed entirely of continuous variables, accounted for 56% of the variability in Db Using only state factors and morphology as nominal variables, the Field Model explained 69%. A combined Field + Lab Model accounted for 72%. Restricting the data set to samples derived from loess and glacial till generated a Field + Lab Model that explained nearly 80% of the variability in Db for a subset of 402 horizons.
This paper examines soil and land degradation. It describes basic processes and factors responsible for degradation, illustrates the cause-effect relationships and differentiates between natural and man-induced regressive effects. The 'critical limit' concept is described in terms of properties beyond which the soil will not support an economically-viable agriculture. This paper is not an exhaustive literature review but emphasizes the scientific principles involved and highlights natural against man-induced processes. Important natural processes are: laterization, hard-setting, fragipan and clay pan formation, and geologic erosion. In comparison, man-induced processes consist of: soil compaction, accelerated erosion, desertification, salt accumulation and leaching and acidification. One of the principal constraints is the problem of data reliability. A reliable database and precise criteria are definitely lacking and hinder the assessment of the extent, type and degree of soil degradation and establishing the cause-effect scenario. Improving our database is, therefore, of a high priority if we are to adopt land use policy for sustainable soil management and long-range resource management. Also outlined, are vital research and development strategies. Judicious resource management policy should emphasize managing prime agricultural land to produce to its maximum potential so that there is no need to cultivate marginal and easily-degraded fragile ecosystems. A strict code of conduct is needed for utilizing marginal/fragile lands. Methods of restoring the productivity of degraded lands must be researched so as to minimize the need to clear and develop new lands.
Abstract. Through the groundscatter process the Super Dual Auroral Radar (Super-DARN) has become a powerful tool for studying F region gravity waves. However, the measurement of the gravity wave position is not direct and relies on an assumption relating ground scatter distance to reflection distance. In previous studies it has been assumed that the tilting of the ionospheric reflecting layer was negligible. Hence the gravity wave distance has been calculated as if the reflecting layer was strictly horizontal. Using virtual height data from an ionosonde and ray tracing, we show that this assumption leads to a systematic error of about 16 % in the positioning of the ionospheric reflection point, with the error more than 30% on occasion. Using ray tracing, we obtained an improved relation between ionospheric reflection and ground scatter distances. With this improved distance calculation, we have found the direction and velocity for a number of gravity waves. These waves were found to be traveling equatorward, usually, with velocities between 50 and 280 m/s, in agreement with previous gravity wave observations and with the notion of filtering by the thermospheric wind. In some cases the source locations were determined by using gravity wave dispersion. These locations were found to be on the poleward side of the auroral oval during periods of weak, but observable, magnetic disturbance. Our raytracing studies found that the strongest features were due to gravity waves of 3-20 km amplitude.
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